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Everything You Need to Know About the 18650 Battery

This article tells you everything you need to know about 18650 batteries. We'll talk about different types, features, charging, lifespans, and our recommendations for batteries and chargers.

18650 batteries

What is an 18650?

An 18650 is a lithium ion rechargeable battery. Their proper name is “18650 cell”. The 18650 cell has voltage of 3.7v and has between 1800mAh and 3500mAh (mili-amp-hours).

18650s may have a voltage range between 2.5 volts and 4.2 volts, or a charging voltage of 4.2 volts, but the nominal voltage of a standard 18650 is 3.7 volts.

There are two types; protected and unprotected. We absolutely recommend protected cell 18650 batteries. Protected cells include a protection circuit that stops the cell from being overcharged.

Unprotected cells can be overcharged and burst and potentially cause a fire unless there are specific electronics to protect the battery. The popular LG HG2 and INR and Samsung 25r and 35e are UNPROTECTED batteries, only use them in a device designed to use unprotected 18650s.

We also recommend you stick with high quality “brand name” 18650s. Many knock off, no-name brands lie about high mAh (capacity).

The average 18650 battery charge time is about 4 hours. Charge time can vary with amperage and voltage of the charger and the battery type.

Recommended 18650 Batteries

Battery Make and Type
All are 3.7v Lithium Ion (Li-ion) 
Max Milliamp hoursNotes
*Shop around for best price*
Orbtronic 18650
3500 mAhOnly available direct from vendor
good price
Olight ORB-186C35
3500 mAhOk price
Nitecore 18650 NL1835R
3500 mAhGood for travel, expensive.
Has micro-USB charger port so it can charge itself with a cable/usb port
Panasonic NCR18650BD Button
3180mAhLess expensive PROTECTED and good for high drain devices.
Panasonic NCR 18650 3400mAh NOT PROTECTED
3400 mAhLess expensive but is
Use carefully.
Panasonic NCR18650BE
3200 mAhLess expensive but is
Use carefully.

More info on the 21700: Everything You Need to Know About the 21700 Battery

Various Battery Sizes

The following is a picture showing various battery sizes. The 18650 is 1170 cubic mm, the 14500 and AA are 700 cubic mm, the AAA is 467 cubic mm.

Note the 14500's cannot be used in all AA devices unless they support both 3.7 and 1.5 volt batteries. The 21700 at 1550 cubic mm, is larger than the 18650 battery – the 21700 and 18650 is not interchangeable.

comparison of AAA, AA, 14500 and 18650 batteries

Comparing 18650s to Other Common Batteries

Battery Make
and Type
RechargeableVoltageMax Milliamp hoursWatt hoursLength & Diameter
Nitecore 21700
(not an 18650 included for comparison)
YES3.7v5000 mAh18.5L: 74mm (2.92 in)
D: 21.4mm (0.84 in)
Orbtronic 18650 Protected Battery
YES3.7v3500 mAh


L: 65mm (2.55 in)
D: 18mm (1. in)
XTAR Li-ion 14500
(not an 18650 included for comparison)
YES3.7v800 mAh


L: 50 mm (1.96 in)
D: 14 mm (0.55 in)
Energizer Lithium AA
(not an 18650 included for comparison)
NO1.5v3000 mAh


L: 50.5 mm (1.99 in)
D: 14.5 mm (0.57 in)
Eneloop Pro AA
(not an 18650 included for comparison)
YES1.2v2550 mAh


Energizer Lithium AAA
(not an 18650 included for comparison)
NO1.5v1000 mAh


L: 44.5 mm (1.75 in)
D: 10.5 mm (0.41 in)
Eneloop Pro AAA
(not an 18650 included for comparison)
YES1.5v950 mAh


12v car battery
(included for comparison)
YES12v40,000 mAh


18650 Terminology

A battery might say protected mode 3.7v 18650 3000 mAh low self discharge for high drain devices. What does that all these features mean?

  • “protected mode” means it has an overcharge and overdraw circuit protection built in (more info below).
  • “3.7v” – is the optimal or peak voltage. It will drop as you use the battery.
  • “3000 mAh” measures the amp hours the battery can provide. A higher number is better. The highest realistically available on an 18650 today is about 4000 mAh, anything higher than that is marketing hype.
  • “Low self discharge” is a good thing. That means it will hold a charge in storage. The less it loses in storage the more charge will be left for you to run your flashlight or other device.
  • “for high drain devices” – the battery is optimized for high drain devices. These are devices that use a lot of power very fast, such as RC toy car.

Protected vs Unprotected 18650 Batteries?

Protected 18650 batteries have an electronic circuit. The circuit is embedded in the cell packaging (battery casing) that protects the cell from “over charge”, heat or “over discharge”, over current and short circuit. A 18650 protected battery is safer than an 18650 unprotected battery (less likely to overheat, burst or start on fire).

Unprotected 18650 batteries are cheaper, but we do not recommend their use. Unprotected batteries should only be used where the load/draw and charging is externally monitored and controlled. The protected batteries normally have a “button top”, but check the specifications to make sure. Generally 18650 flat top batteries do not include the protection circuit.

If any 18650 battery is damaged or looks corroded or appears to be leaking, get rid of it at a battery recycling center. Be safe.

See “Battery Recycling – How to Recycle Different Battery Types and Corroded Batteries Safely“.

How much power does an 18650 have?

A 3.7v a 3400mAh 18650 stores about 2 aH to max of 3.5 aH. It can store about 10 to 13 watt hours. A small air conditioning unit that can cool about 9000 BTU uses about 1100 watts per hour. So it would take more than 110 of the 18650 batteries to run the air conditioner for 1 hour.

In comparison you would need three 12v 40 amp car batteries. But 110 18650s are smaller than three car batteries.

How many times can you recharge an 18650 or other battery?

Recharge cycles vary and are limited. Think of it like a bucket. The trick is that the bucket also gets filled with a tiny bit of other junk over time, so there is less room. As the battery is reused (recharged), the battery degrades due to oxidation and electro-chemical degradation.

This happens to any rechargeable battery such as an 18650, 21700, 26650, 14500, AA, AAA or even a car battery. They can only be recharged a limited number of times.

You want to select rechargeable batteries that can be recharged many times. We specifically recommend 18650's because they have the ability to be recharged 300 to as many as 2000 times.

How frequently should I recharge my 18650?

The way you recharge your battery impacts the life of the battery. If you can measure it, you want to deplete from 3.7v down it to about 3v before you recharge. If you are not sure, use the device until it indicates a battery needs to be replaced. For a flashlight, run it till the light is dim or goes out.

A good charger will tell you the voltage of the battery so you can eventually get a sense of the life of the battery in various devices. If you recharge too frequently you “use up” the life without a return.

Some people don't let it dip below 3.3v (or even higher). Each brand and model of 18650 has different maximum cycles. So this is really a process of matching your device and usage to the life cycle of the battery.

Be aware that an 18650 battery that drops below 2.5v may “lock” the device so it can't be used. The “lock” function happens in devices such as vaping devices.

How do I know my 18650 is Dying?

Here is a list of 7 ways you can tell if you need to get rid of an 18650 (or other rechargeable battery). Look through these to determine if your 18560 is nearing the end of its life and needs to be retired:

  1. The battery will lose a charge on the shelf must faster than normal. It loses it's charge after a couple of days or even worse overnight.
  2. The battery gets hot when charging or discharging, warmer than normal.
  3. You have used the battery frequently over 2 to 3 years.
  4. The battery can hold less than 80% of its original capacity.
  5. Recharge time gets abnormally long.
  6. If there is ANY cracking or deformation in the battery.

These are the 6 signs your 18650 is dead and it is time to get a new one. If you ignore these warning signs you risk fire or even having the battery explode while being recharged.

How can I measure the quality of an 18650 if I am unsure of the age of a battery?

A trick is to buy one or two similar 18650s and mark them “new” with a Sharpe (or label them A, B, C, etc). Then use them and compare their voltage and discharge rates with the questionable 18650s.

Basically you are comparing good vs unknown this way.

You can also gauge temperature this way. Charge both the new and unknown one to see how hot the new one is compared to the one you are unsure of.

18650 Battery Chemistry

There are a number of different chemical combinations for 18650 batteries. We recommend that you focus on protected mode, the chemistry can change and isn't always reported. Many simply say Li-ION (meaning Lithium Ion).

There are actually a number of Li-Ion batteries. Here are some of the current “types”. Depending on your device type one might be better than the others.

  1. LiFePO4 which is Lithium iron phosphate
    • also known as IFR or LFP or Li-phosphate
  2. LiMn2O4 which is Lithium manganese oxide
    • also known as IMR or LMO or Li-manganese (high amp draw)
  3. LiNiMnCoO2 which is Lithium manganese nickel
    • also known as INR or NMC (high amp draw)
  4. LiNiCoAlO2 which is Lithium nickel cobalt aluminum oxide
    • also known as NCA or Li-aluminum
  5. LiNiCoO2 which is Lithium nickel cobalt oxide
    • also known as NCO
  6. LiCoO2 which is Lithium cobalt oxide
    • also known as ICR LCO Li-cobalt

What are 18650 batteries used for?

Flashlights, electronics, laptops, vaping and even some electric vehicles use 18650s. The Tesla uses 7180 of these batteries. Many high lumen flashlights such as the Thrunite TC15 v3 (best buy) or Fenix PD36 TAC (mo43 durable) use the 18650 or the even larger 21700 flashlights like the Nitecore P20iX a 4000 lumen flashlight.

Laptops and other electronic devices use one or more 18650’s and have recharging electronics built in. 18650's are also used in vaping (smoking) devices.

18650s are are generally Lithium Ion batteries. If you are familiar with electronics you can change out some battery packs manually, but be careful – using the wrong type of 18650 or using it incorrectly can cause a fire.

Which is the Best 18650 Battery?

best 18650 battery - orbitronic

Overall best 18650 battery – The Orbtronic 18650 battery. This is an 18650 3.7v 3500mAh Protected cell. This is a high drain battery. We like it but it is expensive.

panasonic 18650 battery

Best low cost 18650 battery – The Olight ORB-186P26 18650 2600mAh 3. The Panasonic 18650 is an 18650 3.7v 2600mAh Protected cell. This battery is less expensive and slightly lower amp hours than the Orbtronic. Also, this lower cost protected 18650 battery is still more expensive than the unprotected ones.

What is the best travel 18650 battery?

Nitecore NL1834R available directly from Nitecore. This is an 18650 3.7v 3400mAh protected cells with a built-in micro-USB charger. It is a few dollars more, but it allows you to charge it on the go and not have to carry a dedicated charger. The unit we have has slightly different packaging.

The cheapest decent one is the Titanium Innovations 18650 at 2600mAh. It won't last as long as the 3400 mAh Nitecore but is 1/2 the price.

What 18650 Brands are Best?

The Orbtronic, Olight, Samsung, LG, Panasonic, Surefire, ThruNite and Nitecore are good reliable 18650 rechargeable cells. Be sure to buy them from a reputable source such as BatteryJunction or direct from the manufacturer. Note: Amazon stopped selling 18650s.

We don't use the lower voltage and amperage 18650s, because they have lower amp hours and low peak wattage and lower sustained wattage.

We are willing to pay a few more dollars for the longer life, higher capacity and better quality.

18650 Battery Charger

18650 batteries are rechargeable, so you will need a good charger. We use two different 18650 chargers.

best 18650 charger

The best 18650 battery charger is the Nitecore UMS4 Battery Charger because it can charge pretty much anything.

Specifically, it supports: lithium ion 26650, 22650, 21700, 18650, 17670, 18490, 17500, 18350, 16340 (the 16340 is also known as RCR123), 14500, 10440 and Ni-MH and Ni-Cd AA, AAA, AAAA, C rechargeable batteries. This is our favorite charger for the 18650s.

18650 battery charger

Our runner up and “best buy” is the XTAR X4 Charger. It is a USB powered 18650 charger. It charges the batteries with any USB power source. This unit is dependent on the power source, and is a bit more expensive.

It has an LCD display for charging status. A 2amp interface yields slower charge speeds. Even the 5amp is slow because it charges at .5 amps. We have used the XTAR and Nitecore with a Nektek solar panel that has a 2amp USB interface and it has worked well.

18650 Flashlight

best 18650 flashlight - Fenix PD35
low priced 18650 flashlight

The best mid priced 18650 flashlight is the Thrunite TC15 2403 lumen flashlight. It is about 1/2 the price of the PD36 and but a bit less bright. It is a GREAT buy (we have the older TN12 in emergency kits). We suggest two of these instead of one of the Fenix.

It has the following modes: Strobe (975 lumens for 226 minutes), Turbo (975 lumens for 126 minutes), High (652 lumens for 199minutes), Medium (266 lumens for 9.7 hrs), Low (19 lumens/177 hrs) and Firefly(0.29 lumens for 62 days) and it can charge itself with a USB power source. It is waterproof (IPX8) and has a max throw of 223m (764ft).

The toughest 18650 flashlight is the Fenix PD36 TAC. It is not cheap but it is durable and very bright, and has a pocket clip. The light level is 1000 lumens, and it is water resistant to IPX8. This is a “duty” quality flashlight.

The PD36 TAC offers five different brightness levels and strobe:

  • Turbo: 3000 lumen – 1 hr 30 min
  • High: 1000 lumen – 3 hr 15 min
  • Medium: 350 Lumen (8hr 24min)
  • Low 150 lumen – 18 hr 45 min
  • Eco: 30 lumen – 160 hr
  • STROBE (about 3hrs 2000 lumen)

It has a 300 yard or 274 meter throw.

Both the Fenix PD36 or the less expensive ThruNite TC15 are great LED Flashlights that use the powerful 18650 battery.

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  1. Apparently, I have lost my ability to find a specific battery for my husband’s solar, windup System: emergency radio. Here ar voltagee the specs. for the battery pack. It takes 2 of these:
    Lithium-ion battery pack
    Model:XTT 18650 2000mAh Material System: Temary Lithium
    Normal voltage 3.7V Charging cut-off voltage: 4.2V
    Specs. 18650-2000mAh-7.4Wh (ofcourse0 MADE IN CHINA TCT200302B004

    1. I suspect that pretty much any 18650 can go in it. The question is it protected or not? To be safe I would use a protected mode 18650. Ones to consider Panasonic NCR 18650BD 3180mAh Protected, or Panasonic NCR 18650B Protected or the Samsung 35E Protected Button Top 3500mAh

      Note the extra capacity might mess things up but i doubt it. Most likely it will just run longer. Those should be readily available, really any “Protected Mode” 18650 battery from: Panasonic, Sanyo (NCR), LG, Orbtronic, Samsung, Olight, Fenix, Tenergy or Klarus. Acebeam and JetBeam seem popular but I have never used those. If you want absolutely safe the Samsung 20R (2000mAh) should be pretty much a 1 for 1 match.

  2. Do they make a flat top 3.7 volt LiFeP04 in a 18650 form factor? I want something safe since it goes in a toy. Or maybe an Alkaline non rechargable 3.7 volt flat top?

    1. Yes there are LIFPO4 batteries. You can find them on Amazon and at a few other online battery stores. In comparison, a Li-ION 18650 should weigh roughly 45g to 48g and the LiFePo4 are about 41g so slightly lighter but also about 40% less capacity, compared to a 3500mAh Li-Ion 18650. I still recommend the boring Li-Ion 18650s.

  3. I have several battery question:
    I have a 4-cell UV flashlight from some Chinese manufacturer (I have no idea who made this). They connected all the UV LEDs in parallel, and built-in a constant voltage converter to convert the battery voltage to a voltage that can power the LEDs. Unfortunately, since the LEDs were wired in parallel, 3 of them burned out, and the 4th wasn’t in very good shape.
    I rebuilt the LED portion by replacing the LEDs with a modern UV LED chip, mounted on a small MCPCB and drove each LED with a 1.4A driver board. That works fine.
    My issue is with the batteries. There are 4 ICR 18650 button-top batteries (3.7V @ 2200mAh) connected in parallel. The flashlight has some sort of built-in charging circuit driven from a small USB charger. There is a charge indicator on the flashlight that glows green when the batteries are fully charged. This thing charges them, but seems to take a while.
    Anyway, I fully charged the batteries and left it away from the charger for about 2 weeks, expecting the batteries to hold a charge. After this time, the batteries were dead and the flashlight wouldn’t light.
    I have several questions:
    1) I am concerned that the batteries didn’t hold a charge for very long. Are there other batteries that would hold a charge for a longer time?
    2) Should I be using protected cells? Should I wire a 3A micro fuse in series with each battery?
    3) Should I even charge these batteries in this flashlight, or get an external charger and change the flashlight switch to run the driver boards directly from the batteries (bypassing the internal charging circuit). The driver boards have a current-source buck converter on them.
    I am now fairly nervous to charge this flashlight, not knowing if I am going to cause a fire.
    Thank you for your help.

    1. Q1) I am concerned that the batteries didn’t hold a charge for very long. Are there other batteries that would hold a charge for a longer time?
      A) 18650s are fairly consistent with the variance being mAh. A higher mAh battery will last longer (all other things being equal).

      Q2) Should I be using protected cells? Should I wire a 3A micro fuse in series with each battery?
      A) Sorry, I can’t answer that. I generally go for the protected mode battery to avoid problems. However, some devices are specifically designed to use non-protected batteries. You need to confirm with the device manufacturer to confirm.

      Q3) Should I even charge these batteries in this flashlight, or get an external charger and change the flashlight switch to run the driver boards directly from the batteries (bypassing the internal charging circuit). The driver boards have a current-source buck converter on them.
      A) Again your expertise on the specific device is higher than mine. As a general rule I use an external charger (that can test mAh and IR/Internal Resistance. That way I know my 18650s are all roughly same mAh/capacity – especially in multi-battery devices. I have spare 18650s so I can grab fresh ones and then charge/test at my leisure.

      General comments: For anything in parallel you want the batteries to be quite similar. Lets say you have four 18650s in parallel – then you want all four to be 3500mAh (or whatever amperage you pick)- don’t mix 2200s and 3500s. I currently have no multi-18650 parallel devices and only had a laptop that used a series of 3, which again I made sure were all the same “profile” (mAh and IR) – but don’t have that laptop any more. For flashlights and other devices with internal chargers – I still use an external moderate to high end charger because it lets me analyze the 18650s (so I dont use a battery that is labeled 2200mAh that is actually 1100mAh and then get surprised with low runtime).

      Keep us posted on your success.

  4. I have built an 18650 battery pack with a 3s BMS module, what would be the best way to charge this pack and when would I know when it is fully charged? Thanks.

    1. Maybe the documentation for the 3S module would help? Also note the process/procedures/measures could vary if the batteries are protected vs unprotected mode and how many you have in series or parallel. Sounds like an interesting project but I dont really have any other advice.

  5. The 18650 I am looking for has a concentric ring PC board on one end so that both terminals are available at that one end. Is there a name for this type of connection? I know that it is not “flat top”. Can a regular battery be modified? I could forward a photo if that would help. Thank you for your help.

    1. You would need to compare the voltage and amperage requirements for the device to make sure you are actually dealing with an 18650 if it is not standard. Further, you would need to confirm that there were no embedded electronics, ie. the button-top is an example of an overcharge protection circuit, and there could be something like that added to perform other functions. Worst case if the device is dead, you could just try a standard 18650 but you might fry the device and/or battery doing that, so I cannot recommend that.

      Even with a picture I could not make a good suggestion, sorry. Best of luck.

  6. Hi August,
    I have a Philips Fc6168 portable hand held vacuum cleaner.
    The batteries are 18650 and seem to last with no discharge at 4.1 volts.
    There are 5 in series making it about 20 volts. The spec says its an 18 volt unit.
    My problem is that the motor draws over 6 amps when running.
    It is now running for only about 1 minute.
    I am guessing the cells are now getting too old to use ??

    Does the 6 amp I measure mean that each cell ( all 5 of them) must be 6000mah units ?
    Does such a cell exist, as all reference I see about these cells is 3.7 volt and 2500 mah ??
    And I see 6000 mah units on the net, but they are 2 sets of 3500mah units ?

    Many Thanks
    Leo Murray

    1. I cant be sure. The problem could be any number of things including shorts, bad charging. 18650s go up to around 3500mah NOT 6000. So 5 would be between 15000mah or 15amps to 17500mah 17.5amps. The amp hours is runtime ie capacity/power. For parallel/serial that can change also.

      The easiest suggestion is replacing them exactly as they are, with fresh 18650s that is probably your best bet (assuming that isnt crazy complicated).

  7. An amazingly complete article on the 18650 battery and it’s on a website that does not specialize in tech… Amazing!

  8. Dear Sir, Thank you very much for all the information provided. I have still one question: Is an 18650 Li-Ion battery recommended for a stanby application like a small UPS? You can look at it like an unending charging cycle… What could be the life span expectancy in such an application?
    Thanking you in advance, HB

    1. Yes many UPS’s use 18650s or 21700 batteries, in packs. That is why an 18650 is called a “cell”. They will discharge and recharge 500 to 1000 times depending on the cell.

      If you discharge “less” and recover, then it could be even more. Say the battery is rated for 500 discharges if you discharge only 50% it would likely last about 900 to 1000 recharges. Battery life is “devil in the details”, based on actual load, temperature, charging cycle, materials if there are any bad cells in the pack. How good the electronics are to control the charge – etc etc.

      Under normal use if the battery pack supports 500 recharges that means the UPS could handle 500 “events” where it needed to recharge. A caveat is that if there is minor draw over time (brownouts, brief blackouts) all would count as events so that will need to be included in the calculation of “events”.

  9. Hi August!
    I have read some of your comments and I find it very interesting. thanks for the clarity of the explanations! 🙂
    I’m contacting you because I have a doubt and I think your experience can help me: Here’s my question: I have 18650 cells, 3.7V 2200mAh with specs: standard dicharge current = 0.5C; max continuous discharge current = 5C; cutt-off voltage= 2.75V.
    Here is the part in datasheet that intrigues me:

    5.6.2 Cycle Life 循环性能
    The rest time is 10min after using 0.5C charge. Then the cell will be discharged to 2.75V using 5 C, The rest time is 20min after discharging. The test shall be terminated when discharging capacity ≤80% of initial capacity in three consecutive cycles. Temperature of standard charge and discharge is 25±2. Cycle time≥ 800 times

    The manufacturer says that discharging the cell up to 2.75V (cutt-off voltage) with 5C (11A!!), the cell will have 800 cycles of life? Is that possible?

    Many thanks for the all the help you can give me!

    1. You are at the edge of my expertise. I can say life cycle is normally about 300 to 500. It is theoretically possible to do more. Some better AA batteries can approach or slightly exceed 1000 recharges. I would follow their recommendation regardless (if possible).

  10. Hi August,

    I am trying to find a charger for a 2600 mah sony 18650 batteries. Unfortunately I cant find anything that specifically states it is compatible. I have a cheap XTAR charger for it that randomly doesn’t charge the batteries at all. Any suggestions?

    1. All 18650 batteries can be charged with a decent 18650 charger, UNLESS the battery is junk. I have an XTAR and have consistently charged 18650s from numerous providers.

      Try the charger with other 18650s if it consistently works on other batteries you may have a bad cell. If the charger is random on all batteries, you need to get a new charger. They do die randomly. I recently had a really good AA/AAA charger die after 15 years.

      Best of luck.

  11. I have a Black & Decker “Gyro” screwdriver and the battery, 18650, is dead. The way this battery is installed in the screwdriver is with soldered connections. Unfortunately, I cannot find a 18650 with soldered wires or connections so, my question is, can I solder a wire to each end of the protected-18650 battery? At Battery+ I was told they would explode if I did. Thanks.

  12. Have bought a cheap solar sensor light – directions were to charge for 3 days before using – winter here and not much sun where the panel is – it has basically gone flat after 3 nights with not that much use – the batteries are labelled ICR 18650 but are only 1500mAh – no name batteries with flat ends – would it be ok to replace the batteries with higher mAh ( the specs also say to charge for 5 days when storing – I am wondering if the batteries are from way back as the model of the light has been around for a while)
    Thanks for a great resource

    1. August is up to his eyeballs at work, so I’ll jump in.

      Given that the light’s not working, it would seem that you have nothing to lose. That said, I’m sure battery swapping would void any warranty. Ideally, I’d contact the manufacturer and ask them directly, but I know that’s not always possible.

  13. Good morning. Wonder if you might help. I have a set of 18650 batteries in a Dremel tool I would like to replace. The battery data is


    Not sure what this data means. Where would you recommend I look to buy these? I’ve watched the videos, understand will need to solder. Any ideas?

    Thanks much

    1. the LGCH118650 appears to be a custom non-USA pack (German I think). If you can solder, it looks like you could use any good 18650s (probably protected mode). I am unsure what the F1511026510 code is or the HE311C2H1 code means (no luck searching). I cannot guarantee standard 18650s would work but probably about a 80% chance.

      1. The batteries are attached to a board. Not sure if that board protects the batteries or if it has more to do with the function of the tool.

        An you suggest a manufacturer and website to buy these batteries?
        and what is the best place to buy?


  14. Hi. I have just bought an RC car which came with a 7.4v 1500mah 25c battery. I bought 2 spares off ebay but both last about a minute before the cars lvc kicks in and the car dies. The original battery lasts around 5-6 minutes. I would like to build a battery with known good parts (eg samsung 18650’s). I know how to build the pack with all the necessary wiring etc but my question is can I put in a higher capacity battery like – Samsung 25R 18650 x2? The Samsung battery is not protected but I have a balance charger and the car has LVC in it.

    1. 99% chance you can use a 18650 with a higher mAh. Going from a 1500 to 3000 should roughly double the runtime. Note a number of RC cars and especially drones use LiPO variants which are much lighter, those are NOT 18650 batteries. Good luck and let us know if the math matches reality.

      1. For RC Lingo, you are running a 2s battery (s=series, and there are two 3.7v cells ran in series inside an RC 2s battery). 18650 or L-ion type lithium batteries aren’t often used because they do better with a steady draw, to where Lithium Polymer (Lipo pack) battery, can handle the rapid and sporadic high voltage draw associated with RC cars and drones. Not sure what kind of RC car you have but you want to pay attention to that “c” number, which relates to how well the battery handles rapid/burst voltage, 25c is pretty low. and could cause what’s called “voltage sag” like when your car sputters low on gas. If you’re just cruising around the park, not a big deal, but if you’re off road and going fast, you’re going to want closer to 50-75c at least. Racing drone pilots won’t use anything under 100c.

        Like August stated, weight is an issue too, but not as much for land vehicles as drones. Milliamps (mah) is the biggest factor, the more mah, the heavier, but the longer run time. A good analogy I once heard, the voltage is like how powerful your car engine is, and mah is the gas and size of your gas tank, the bigger the tank, the longer you can drive, but the heavier your car is.

        Make sure you know the voltage rating of your vehicle and it’s parts too. if it’s 12.6v, then you could move up to a 3s battery, often they are rated by “s” type, like 1-3s capable. Remember a 2s lipo pack will have 7.4v labeled on it, because when at storage level and the way they are shipped, is appx 3.7v per cell, fully charged it will be 8.4v, when not using a Lipo pack, they should ALWAYS be stored in a safe place at storage level to get the most cycles (longest life) out of them. Most decent chargers have a setting to put a Lipo pack at storage level. Always charge/discharge in a safe place, NEVER unattended, preferably using an ammo box or other “lipo bunker” (type that in youtube, tons of videos), Lipo packs don’t have a hard casing as 18650s and L-ion type batteries, meaning they can puff or have a cell let loose, causing thermal runoff and very bad things to happen. August is not joking about their energy potential, I’m a retired firefighter, and I’ve had a couple let loose on me over the years, they are no joke. Be safe, hope this helps.

  15. I have a flashlight with 18650 ( 1200 mah ) battery. The battery suppose to give 2 – 3 hours backup as per flashlight specification. But i observed after 40 minutes, the light started getting dimm and if i switch of flashlight for an hours and turn it on again, it starts with bright ( as expected ) then with in 1 or 2 minutes the light get dimm again. Is it due to battery capacity degradation ? Or something wrong with battery ?

    1. The easiest test is get a different fresh 18650. A 1200mah seems low, a 2500mah or 3500mah battery is going to give you longer runtime. Note: The 18650’s are not readily available on Amazon right now, but they are available at Battery Junction.

      My suspicion is that it is up to 3 hours with a fully charged high mah 18650.

  16. I think it would be wise to add something about the difference in rated nominal capacity vs rated discharge current. As a general rule , the more of one you want, the more of the other you have to sacrifice. Which will vary depending on your device. Examples:
    Samsung 20S (unprotected) has a rated capacity of only 2000mAh but has a rated discharge current of 30A.
    A Panasonic NCR18650B (unprotected) has a rated capacity of 3350mAh but rated discharge current is 4.87A.
    Using these examples above, depending on your particular needs, you can actually get more life and performance from the Samsung 20S if you had a particularly high drain device. This is, of course, not including the protected cells which generally have a cut-off around 5-10A depending on the model. They change the chemistry depending on the current vs capacity need. Choosing the wrong one can cause bad life, performance, excessive heat, and in the worst cases, thermal runaway. Also, you have to beware of brands that advertise a “burst” or “pulse” current. These manufacturers rarely state what exactly the “pulse” conditions they used to get that rating so it could be way over rated. Usually “max continuous current” is what the more reputable companies use and is the safest one to use. Finally, is a very good place (not affiliated with them in any way besides being a repeat customer) to get cells from. The shipping is always fast , they have genuine Samsung, Panasonic, Nitecore, Sony, Sanyo, brands (others too), and they include free cases with every battery. They also give detailed specs in an easy to read format for every cell. You should check them out.

    1. Agreed, we have it in the lower notes, but I will note it. Draw and actual amperage vary with charge, temperature, load and charge level (and of course between batteries). Also since amazon doesn’t seem to carry them we also like Battery Junction (and we dont get any money from them either).

  17. I purchased a 6 cell lithium ion battery pack with no markings except 21.6V 28,100 ah. The individual cells inside are generic and have zero markings on them. I do not think is is physically possible to create such a battery pack using 6 18650 batteries and some protection circuitry. Any opinions out there? They are chinese and the vendor says the spec is correct and challenged me to prove him wrong. Of course, I tore it apart and its extremely low quality, high internal resistance cells inside.

  18. Wait! Found this… m4potofu
    2 years ago
    · edited 2 years ago

    that this battery is protected ?

    It’s not, cells from original manufacturers ( i.e. lg, sanyo, panasonic, samsung, sony) are not protected and have a lenght of 65mm, protection circuits are added by other compagnies (sometimes flashlight compagnies) such as redilast, keepower, eagletac, nitecore… , they are always longer generally 68~69mm, also a bit thicker and more expensive.

    Like kamil4 says you need a relatively high drain cell for this flashlight, like ~>8A to have headroom and more longevity (because less heat generated), no need to go super high like >15A, as you have a trade of with capacity.

    From the website you have linked you have this one for example : KeepPower 3500mAh Sanyo NCR18650GA based on the Sanyo GA and is rated a 10A continuous discharge current.

  19. Protected v. unprotected recommended brand. Can you assist me in finding a flat top, protected, reliable 18650 for a Zebralight H600c Mk IV 18650 XHP50.2 4000K High CRI Headlamp for my hubby who wants to thru-hike the AT. Zebralight website has Sanyo NCR18650GA 3500mAh 10A, but it’s unprotected. Too many no-name brands on Amazon! I’m scared of the unprotected name brands. Ty Obi Wan, you’re my only hope.

  20. I hope this helps I believe you are correct you have a 4S2P that will give you from 2P double the current of each battery and the 4S will give you 4 times the Voltage.

  21. Hello,
    Could you comment about batteries in series versus batteries in parallel to change the output voltage and the capacity?
    I have a custom design LED display and I need to replace the battery pack. (I purchased the LED display from a supplier in China.) Looking at the battery I can see one row of 8 cells. And I know they are 18650 cells with 3.7V per cell.
    I also know that the voltage output is 14.8V. I think each cell capacity is 2200 mAh.
    Even though the pack is 1 row of 8 cells, they can’t all be in series, correct? If that were the case, the output voltage would be 29.6V? Is it possible that the wiring of the cells is 4S2P?
    If that were the case, the voltage would be correct, (4×3.7V) and the capacity would be 2200 x 2 = 4,400 mAh.
    But the supplier is giving me 14.8V 2,200 mAh and that’s it. I think they are wrong, but I’m not sure how to confirm.
    Let me know your thoughts. Thank you.

    1. My brain is distracted this morning, but I hit up clear thinking friends, and here’s the verdict:

      “Voltage is correct for 2 paths of 4 cells = 14.8 volts. mAh will be 4400 mAh (2200 x 2).They should be able to load the battery pack to 4400mA for one hour … 2200 mA would take 2 hours to deplete the batteries.”

      1. Hello Laurie,
        Thank you for your reply and for the help of your colleagues.
        This partly answers my question.
        I’m also trying to figure out the “configuration” of my battery pack.
        I need to know if it is 8S or 4S2P.
        From “the looks of it”, there are 8 cells in a row. (I wish I could upload a pic.)
        But there must be “2 paths of 4 cells” = 14.8V. That’s my guess, because that would equate to the correct voltage.
        I’m not sure how much current the LED display draws when it is fully illuminated. (I was hoping to calculate it… or measure it.) There are 217 individual LEDs on the display. I’m assuming it is much less than 4.4A.
        I guess my most basic question is: Can a battery pack of 18650’s that are physically 8S actually be wired to be 4S2P? (Do you know of any batter suppliers that would do this?)
        I’m basically trying to reverse-engineer what I have so I know what to order. The supplier that I got the display from doesn’t seem to have the technical background. (And I’m just a novice myself…)

        Let me know your thoughts. (You guys are GREAT… by the way!) Thank you!

        1. Ron, some input from the crew:

          “If the 8×3.7V batteries are connected in series (8 batteries in a row), they would produce 29.6V, and the capacity of the battery bank would be 2.2Ah. However, to produce 14.8 V, a Voltage Divider (for example) would need to be added to the circuit. A voltage divider adds resistance to the circuit thus reducing the voltage. I don’t think that a Voltage Divider decreases the Ah or capacity of the batteries, but it would decrease the available current.”

  22. I am so very confused with all the different types of batteries. I have purchased a video doorbell without first looking at the batteries mistake! It asks for the18650 which makes this purchase very expensive needing 3 batteries & charger. Can any rechargeable of the proper size do the job? I realize the benefits to the 18650 but would like to try the item first without a large investment to see if the item is worth keeping.

  23. Hi I just bought a SucbaPro 850 R dive light it says to use TENERGY 18650 2600 mAh Li-ion 3.7v PROTECTED batteries.
    my question is can I use higher mAh numbered batteries to have them last longer or just get what it suggests.
    Is Tenergy a good brand name or do you reccomend something else.
    Thank you.

    1. Tenergy is a good brand (we have a number of them), and higher mAh numbered should be fine – as long as it wouldn’t void any warranty. If you are using within a warranty period, it’s probably best to stick with recommended specs.

  24. Hi Great article. Can you advise I have a battery with LDGBHE41865 cells I want to recondition. Is this the same as 18650 cells? Also the battery is 2S24P configuration so do I have to isolate each cell to test for failed cells as I guess the faulty cells will be lifted up be good cells.?
    Regards Steve

    1. Please contact the manufacturer for advice. I suspect that you may be dealing with 18650s, as they are commonly bundled for use in rechargeable devices, but we are not a battery service company.

  25. Hello . You sure have a lot of info about 18650 batteries here …Thanks …it’s interesting but the more I read the more unsure I am about whay I “Know” …Learning about ebike batteries as mine appears to have died … Do I go with the $300 one on Amazon or the $600 one from the Bike dealer …My dead one came from the dealer …Lasted 3 years Supposto be a Panasonic but upon opening it up it’s LGEBMG 11865 2850 MAH …Good or bad I don’t know much to learn ..discharge rates ..charge rates . I think I may have been charging mine to often dealer says after every trip I was doing it every 5 trips or 30 miles when the yellow battery indicator just started showing …Anyhow would you go with the expensive battery or the cheaper one …Thanks so much

    1. You should buy the replacement battery from the e-bike company or at least buy a pack they approve.

      I am not familiar with eBikes. If you try replacing the individual batteries (ie taking the existing unit apart) You could confirm if the 18650’s still can be charged that way. Take them out and charge them individually to see – using a flashlight to test battery life. But even putting new batteries into a pack could be tricky as the casing is likely sealed, and if the batteries are custom or have specific voltage/amperage profile you could cause serious problems.

      So I recommend sticking with buying one form the bike manufacturer. There could be custom voltage/amperage controls and/or electronics that could cause damage to the bike. I suspect the bike is far more than $300. If you tinker, your are tinkering at your own risk.

      Best of luck.

  26. you don’t explain the different types of 18650 batteries something you should have talked about I have 2 types of 18650 batteries. I have a BMR 18650 battery and a IMP 18650 battery

  27. Great article thanks. Quick question, if I replaced old cells in a battery pack (there are 12) I’d need to unsolder the positive and negative terminals. As these connections would no longer be seeing any voltage would this automatically trigger the low voltage protection circuit?

    If it does how would I reboot it? I thought maybe I could temporarily connect a voltage duri g the swap out to prevent the safety circuit cutting in?


    1. I talked to August (he’s swamped at work), and he said that you’re likely to trigger the low voltage protection, but he hasn’t personally attempted anything quite like this.

  28. I’m buying a protected 18650 battery for a solar charging light in my garage. I only need one, but the S&H is the same as the price of one battery. If I order 2 or 3 and don’t need them for 2-4 years, will they still be good or am I better off just buying the one now and deal with it.

  29. Hi August,

    Is it safe for 18650 batteries to be “plugged in” all the time, for example in applications like emergency back up lights, where they come on only during power outages?


    1. August is up to his eyeballs at work, so I’ll chime in.

      While it might not be ideal from a battery life perspective, if that’s what the device requires to function, that’s what it requires to function. It should not be safety concern (no risk of explosion, etc).

  30. Hi, I just recently started buying LED flashlights powered by 18650’s. I understand the higher mAh batteries give longer runtime, but now I just ordered a “high power” flashlight that says to use “high discharge” rate batteries of 10A or more, so my question is, can you tell if a 18650 cell is “high discharge” just from the numbers/ letters printed on the side of the battery? Thanks, Ed

    1. Some battery types are designed for high discharge, some are “LSD” low self discharge. The high discharge ones generally don’t hold a charge in storage, but do a good job of providing power fast. The low self discharge ones don’t provide power fast but also don’t “leak” power over time. If you have an 18650 battery you will need to research the type of battery to find out if it is normal, low self discharge or high discharge.

      1. Ok, August, so if I understand you correctly, most high discharge batteries will say on the casing “High discharge” or similar- These are the batteries I got; , and I am ordering this flashlight; , which is 3500 lumens- I don’t want to smoke the battery…. Seem like they might work? Thanks, Ed

        1. Ed,

          It would be best to check with the people selling that specific flashlight. We haven’t used that particular product before, and they should know the items they’re selling.

        2. There are far too many general statements here. The author states his opinion of the best batteries and flashlights. Some of my flashlights are definitely better to use unprotected cells for the same reason some of my vape devices do. The protection circuits are sometimes built into the lights now, and protected batteries will not allow the amp draw needed because they are capped at 10 to 12 amps. Also the best light is often based on the intended use…do you need a long throw, more flood, or combination. Some lights now even have proprietary batteries and chargers. That is the case with Olight Seeker 2, but you can actually use an externally charged 21700 orbtronics protected battery with the buttontop closest to the cap. You can’t however charge that battery in the light. The Olight special modified battery re-routs a negative contact to the positive side for the magnetic charging. The negative terminal on the light is at the head.

  31. Please let me be BLUNT! There is no such thing as an 18650 Cell that can deliver over 4000 MAH! NONE Any advert saying that their battery provides this is a Lie False Adverts! and from testing they are usually less than 2400 Mah. Additionally they have a high “internal” resistance, which means that there is a higher voltage drop at higher current levels. My personal guide line would be : Buy Japan or South Korea mfg 18650’s ALL China branded are inferior and/or falsely labeled. Many of the Adverts are just LIES! Amazon and Ebay should stop listing them.

    1. Hi Jaime.

      August is having an extra crazy week at work (they dumped a big project that would normally take months in his lap and want it done this week), so I decided to chime in. For better or worse, the only way to know for sure it to try and see if it works. The odds look good, but you can’t tell for sure until you try.

  32. Hello August: I have a cordless vacuum (Type AE – 14.4V DC) hat uses 4 batteries LGDAHB31865. I searched and find that this refers to a 18650 BATTERY. I want to replace it for equal or ideally better ones. I live in Canada and I do not find the reference above mentioned anywhere other than China. Could you please help me with some brand name, reference o place where I could buy it. I’m older and the vacuum is like new and been working well for me (light and handy), but the batteries are almost dead after 2 years and the manufacturer offers no help even know it is a big Company .
    Thanks in advance
    Jaime R.

    1. Yes the LGDAHB31865 is a High Discharge LG 18650. They appear to be available on eBay. I can’t suggest using any other battery. The risk is that the electronics might be tweaked to match that specific battery (charge/draw). First, idea is to charge the LGDAHB31865 batteries outside the unit to see if they truly are dead (if they dont charge then you know its not your unit). Second idea… I suspect you could use two 2 packs Orbtronic 18650 batteries (I have these). There is a risk that this could damage the vacuum or the new batteries. I suspect the Orbtronic might allow the unit to run longer also.

      Although I cannot recommend it, if you test it out please keep us posted.
      Best of Luck Jaime R, sorry I could not provide a definitive answer.

      1. August, thank you for your prompt answer. I’ll check on eBay to see if they have it. The solution of the Orbtronic 18650 batteries, will be more expensive than buying a new vacuum. Nowadays, it is difficult to find and appliance that last more than 2 years.

        1. Yup that is why they use cheap batteries, everything is about cutting unit costs. might have cheaper one unprotected 18650s (which I suspect that your vacuum is using). We buy the expensive batteries and they last much longer. Again be careful, the electronics could smoke if they had a tight match to the battery specs (and remember unprotected 18650s can burst).

  33. Hello. I have a question that I think will be more common this year with the popularity of outdoor Wifi security cameras, and the solar charging panels to keep the cameras running day & night.

    I have purchased a few of the solar chargers dedicated for Amazon Blink cameras. The Blink cameras run on a pair AA Li-Ion internal batteries, that are advertised to “run for up to two years”. Obviously, replacing the internal pair of AA batteries with a pair of 18650 rechargeable batteries, running from inside a solar panel, to the USB port on the cameras, should do better.

    The Blink cameras’ Chinese aftermarket dedicated solar panels have two 18650 flat top 3.6V 2600 mAh of various branded batteries mounted in the back of the panels; where there is also a bit of circuitry on a small board. The solar panel specs says it outputs 6.0 V, 0.4 A.

    I am curious about what type of 18650 batteries will work best in this variable load/trickle charge situation. The cameras are awake full time 24/7, but not recording and/or sending Wifi radio signals much of that time. The battery usage is a situation where there is a tiny draw full time, and larger draw occasionally when they are motion tripped, and also being recharged maybe 12 – 14 hours a day at various levels of solar power.

    Most of what I’ve seen for the small solar power panels are using lower capacity batteries (2,200 to 2,600 mAh). Aside from price, is that because the charging current from the solar panel is so low (Max 0.4A)?

    I’m concerned about the the “flat top” battery style (not protected?), supplied in the panels, but I used those for years in E-Vape service. Just lucky? I think the high end chargers used, along with the vape devices’ circuitry maybe provided protection?

    Well that’s just one concern. The bigger question is what style/type of 18650 will work best (most durable) for the daily variable solar charging, along with simultaneous variable draw from the batteries. I see a plethora of brands, and models out there, and don’t relish frequently changing out batteries whilst balancing on a ladder . Like some other commentators, price has a lower priority/concern than ladder climbing frequency.

    1. The solar panel USB feed is a good idea. To confirm runtime etc I would need specs on the panel. Two 18650s provide up to 25ah where the two AA provide 9ah. So the panels (if they charge even with lower quality batteries should do far better than the internal AAs and last for years.

      Solar Panel. The wattage (output) of the solar panel and amount of sun it gets is key. If the panel can’t get enough sun the batteries will eventually die.
      Solar Panel 18650. Nearly all manufacturers use the cheapest battery that will perform in the device. Unprotected are cheaper so they build the “protection” into the electronics instead of the battery. If you replace the unprotected battery with a better protected battery it will likely give you better life but I cannot be sure. If the panel gets enough sun it is probably unnecessary to replace the batteries right away. One way to confirm them is remove them and put them in a protected charger to check their max wattage.

      Alternate solution. The 6 MinPak waterproof 6×18650 pack could use your old vaping batteries and still have more than 10x the watt hours. If it works, you could just change them out every 3 to 5 years, recharge and replace. This might be a better pick for wooded areas.
      As I don’t have specs, any “creative solutions” would need to be tested.

  34. I just received a flashlight that uses a 18650 battery. The flashlight says “shustar”, “Albinaly”, and “CE RoHS” in different places. The battery says “shustar”. The wall charger has a light on the plug-in part that glows yellow when plugged in; don’t know if it changes color when the battery is fully charged because I just started charging the battery. Did I get anything worthwhile? I assume the battery is not a protected type.

    1. The best I can say is track back the manufacturer and try to find the specifications and documentation. I do not know which make/model devices you are using. We recommend the better reviewed, name brand flashlights and chargers. The name brand are a few more dollars but you can call for support and they have wider reviews.

      Regarding the battery, we recommend that you use a protected mode 18650 regardless of the device unless it specifies an unprotected 18650.

  35. Hi August, I am one of those species that are naturally inquisitive and will forever “tinker” with everything. the latest being replacing my NiCD batteries in my cordless drill with LI-ion batteries. I have matched the voltage and the drill 18V works fine. I have not yet recharged the batteries.,Can I use my NiCD charger to charge the replaced LI-ion batteries? A friend of mine bought me Rekieta 18650 12000ma/h3.7v batteries from a china shop which I have tried in a similar way on my 14.4v drill, also matching the voltage. Sadly the drill does not work although the voltage is correct. the lettering on these batteries are very foreign and I cannot determine whether they are indeed rechargeable or not. HELP!!!

    1. August is up to his eyeballs in alligators at work at the moment, so not much time for the site.

      From what I was able to find online at this Q&A on Quora “Can I use a NiCad battery charger for lithium?“, the most likely answer seems to be “No. voltage profile, current profile, and current tapering profile are all different.”

      Batteries can explode or have a meltdown under conditions that they were not designed for, so be careful.

  36. Hi. What a useful website!
    I am in the process of changing the Samsung 1500mAh18650 batteries on my AEG vacuum cleaner , it is 5 1/2 years old and they have gone already! (joke). Am I best to replace with the 18650 3500mAh units. Same physical size etc.
    Also, the manufacturer’s instructions are to leave the cleaner permanently on charge. Is that a good idea?

    1. High mAh will in general be safe- it will just run longer (more capacity) – the wattage is 3.7v x 1500 = 5500m-watts vs the 3.7v x 3500 = 12,950 m-watts . The “charge all the time” part is more tricky. It depends on the device, electronics and charger. If you get lower self discharge batteries i suspect you would only want to charge it before use (or after its dead). You really need to confirm with the manufacturer to confirm – if they have another small battery in the electronics the trickle charge could be to keep the unit powered. I cant be sure, so use your best judgement.

  37. I’m trying to use 18650 in a trail camera as directed by the owners manual . The 18650 I bought are Nurie18650-1A , 3.6 v , 2600mAh, it call for 2 batteries in the camera . How do I know if these are the correct battery ? It mentions something about PR200 when discussing the battery ?

    1. I believe you are asking about the PR200 Trail Camera – it looks like that model requires any two 18650s. Although the Nuon NURE18650 will work, it lists that it is a high self discharge battery (it loses charge just sitting around). Also, the Nuon is only 2600mAh. Instead I recommend a 3000mAh to 3400mAh protected mode low self discharge 18650, such as the: Samsung, Panasonic, Orbtronic, LG or Nitecore. Finally, you need to confirm with the camera manufacturer manual for exact information and battery types.

  38. hello, I am a dentist and use my led surgical light powered by battery pack of two pack 18650 2200mah, I just replaced my battery pack with a fresh battery pack. question: how can I make my battery pack last longer?
    use it till it drains and then recharge? or keep it connected to my charger intermittently through out the day as I use is daily???
    thanks Drlopez

    1. Good question. We added a couple sections in the post to answer this. A quick answer is you want to balance recharges with “using up” the battery. Check your specific battery specifications for lifecycle and charging recommendations. In general though, if you recharge before the battery is at least partly depleted you “lose” a recharge – and batteries only have 300 to 2000 total recharges before they should be replaced. Generally you want the battery to drop from 3.7v to about 3v. In other words don’t top off a 3400mAh battery at 3300mAh instead charge it at 2500mAh or even 2000 (where you choose depends on the number of recharges you expect and the devices sensitivity to low voltage/amperage). I hope this helps.

      1. Hi August. I do not agree with you regarding the charging of batteries. If you look at the datasheets of these batteries, you will see that the lesser the drain on the battery the longer the battery will last. It is the same with cellphone batteries, also Li-ion. My cellphone battery get charged every night. Mostly my battery still have 35% to 45% charge left. I have no problem getting 2-3 years life out of my cellphone battery. Years ago people was told to fully discharge the battery before charging. That might have been correct for old battery types like Nickel Metal Hydrate batteries, but Li-Ion batteries give you the best life performance if you can keep them between 40% to 80% charge. I viewed the datasheet of a 100Ah Li-FePo4 battery pack, used for solar systems, the other day. It is rated at 2000 charge cycles, but they gave a graph showing expected life time at different discharge depths between charges. If you don’t discharge it more than 50% you can get almost 20 years life out of the battery, based on every day recharging via solar.

        1. You are correct. It is why I like larger packs where possible (higher wattage at same voltage to allow lower overall drain). And as you noted, this is recommended by the manufacturers and has to do with the design of the 18650 batteries. I don’t follow all the rules, I leave mine in flashlights and other devices until they don’t light up the way I want. So I am not staying in the 40% to 80% range. I don’t worry about the cycle rates because 2000 is awesome but 500 to 1000 is just great too and I don’t have to monitor them all in detail, but if you do you can drastically extend their life. Thanks for the feedback.

    1. After quick research, I believe it is a different form factor of battery. Not an 18650. The “S1 S2 S3 S4 S5” battery, is a brick design for cellphones, specifically a code that matches the form factor for the specific Samsung model. In my mind those are not 18650’s even if they are described as one. They are square or rectangular and thin and unique to a specific device. They use similar technology to an 18650 and fit inside a cellphone, tablet or other thinner portable computing device.

      1. 1s, 2s, is gow many cells in series. series connection will increase voltage, parallel will increase capacity. 1s would be 1 cell @3.7v 2s would be 2 cells connected positive to negative (think old flashlight stacking batteries in handle) @ 7.4, 3 s being 3 cell+-+-+- @ 12.1v and so forth.

  39. I have seen 18650 battery’s advertised with capacities up to 9900 mAh. Are these real? Is that a maximum a 18650 can be in mAh?

    1. The highest current stable 18650 battery is 3500 mAh. I fully expect the research to improve over time. 9900 is not real. Also watch out for batteries without overcharge protection. Check reviews carefully. Best of luck.

  40. im trying to change dead 18650 batteries in a triple drill battery pack
    they have the code SE US 18650VT but i cant work out which battery
    i need, i know they are only 1.5 a/hr…(can i upgrade to bigger) 12v drill
    the other line under that code is..T C112VSG19R.. this is the line i cant
    interperit or find any info on..thanks for any feedback…cheers

    1. It’s probably safest to contact the tool manufacturer directly. If it’s a battery pack (versus individual batteries), they probably have proprietary battery packs and using anything else is likely to void the warranty.

        1. You’re welcome. Sorry I don’t have more specific info, but there are a LOT of different tools out there, and many companies are bundling the 18650s for specific applications, even solar electric systems.

          If you’re past your warranty period on the tool, are handy, and the company is no help, you could try swapping out the batteries in the pack with well rated 18650s. I just snagged August and he’s going to comment more on this option.

    2. We cant recommend any tinkering… but we have done it successfully on a laptop and a simple battery pack (both out of warranty). The risk is that you will damage electronics or even start a fire. Many of the devices are built in a way that you cannot easily access the battery packs. Also some are be designed for a specific voltage and/or amperage. The fact that tons of devices use 18650’s in series or parallel make them a tempting self repair project. All we can say is stay safe and if you choose to tinker and are successful, please leave a comment so others will know too. There are YouTube DIY rebuild videos for various brands of battery packs. All the best.

  41. Hi August. My question is how do I know if my 18650 batteries are not discharging cocorrectly? I bought some Samsung 25R and was notified by the seller not to use them as they were from a bad batch that were not discharging correctly after I had already been using them. They seemed to be working just fine, but I stopped using them anyway. But I have a lot of other 18650 batteris that I use for vaping and would like to know what I need to be on the lookout for. Thanks for your time.

    1. Good question. A bad 18650 can burst or damage the electronics using it. Some electronics have overload protection which greatly reduce the likelihood of damage. Your device may have that protection so the battery is protected once by the in battery “protection” (which might be failing) and again by the device. Regardless, if the manufacturer/seller is recommending not using them, I would stick with that. A burst 18650 is a mess. Get them to give you replacements and move on.

  42. This is the 1st time I’ve ever heard of these and boy am I confused! I’m guessing that you don’t replace your regular rechargeable AA or AAA batteries with these? I’m going to read up and educate myself. This must be something that preppers are into. Love the preppers but the “prepping” is too overwhelming for me being average 65 year old female. Just had to share. I love reading all of the interesting things that preppers are doing. Thanks for letting me share. Debbie

    1. No worries, Debbie. If a device needs an 18650 battery, it’ll be labeled somewhere that it needs one. No swapping out your current batteries required.

      It’s just a way to cram more power in a relatively small package.

      Some preppers use them, I’m sure, but they’re mainly for electronic gadgets that suck a lot of power – like our small LED flashlight that’s bright enough to light up the back of the ten acres from the front of the 10 acres.

  43. Hi August, thank you for putting this article together!
    I bit the bullet and bought a 2018 Lupine Blika headlamp to use on week+ long ski trips here in Alaska. Really only use the 3 watt output setting, the larger bulbs give an unnecessary amount of light and drain a battery VERY quickly.
    The battery pack that came with the head lamp is small and I need more capacity but the larger OEM battery packs are prohibitively expensive. Owner’s manual says the OEM battery packs have 18650 batteries in them so I figured I’d just buy 18650 batteries and make up my own battery packs. Discovered when I went shopping for batteries that there are apparently dozens of 18650 battery types/outputs and I have no idea which one to use. The battery voltage in the owner’s manual says 7.2 volts and it has a visual battery level meter built right into the the battery pack.
    I’m afraid of 2 things:
    I assume the OEM battery pack has circuitry to give a consistent power output so the light stays near the same brightness for the duration of the battery discharge cycle. If I make up my own battery pack, I’ll lose that circuitry and may toast my very expensive headlamp due to too high or too low power input. Is there a stand alone voltage, wattage unit I can buy to put in line to properly regulate my home made battery pack output?
    And, which 18650 battery will be the best for my usage? Because I’m carrying them, low weight and high capacity is necessary.
    Thank you for any answers you have for my above questions and thank you for putting out this great site! Matt Obermiller

    1. Thanks for the positive feedback.

      In response to your comment, the output must match the unit you are using. The 1860 I note in the article is protected mode, so it will not burn up or draw outside spec (that is the battery side). The headlamp battery pack may have a voltage regulator built in. The only suggestion I have is to tinker; but only if you can afford frying one. A lot of the LED emitters circuits will take any 18650 – but some may damage the circuit without protection on the LED side OR they may accept any voltage and work fine.

      The little AA flashlight we reviewed, will use either an AA or 14500 which are dramatically different, so the only way to find out is test it. Watch out for overheating and be prepared to fry your electronics. If you succeed (or fail), would you mind writing a guest post on this? I am sure the community would appreciate the information.

      Regarding weight, all 18650s are all fairly heavy. I have not seen a LIPO 18650 yet, but they might be available somewhere. If you are going for lightweight the Energizer Ultimate Lithium AA are super light but one-time use. You would need an AA based headlamp such as the Fenix HP15 – and then you could pick AA rechargeables such as Eneloop Pro or Tenergy are both good depending on use profile – in your case I think the higher mAh would be better from the Eneloop Pro.

      It really depends on what you are doing. If you are out for long periods the solar panel and rechargeable AA or 18650 would potentially cut your load (and allow you to charge a cellphone or any other USB device) but only if you carried more batteries than the weight of the solar panel. The nektek is 1.3lbs though so unless you need to charge a lot of stuff and are out for a long time this probably isnt an option. (ounces are pounds)

      All the best.

  44. Hi August,

    I enjoy your articles and the great information they contain very much and those of your wife also. I just have one small complaint. Your articles can be shared on social media everywhere for people all over the world but you don’t have a print function. Many times I want to print an article to reference later without trying to remember which website it was on. For everyday living commonsensehome would be one of the first places I would look, but for a certain battery I might have to check seventy different sites and no telling how many articles. Please think about adding the print button.

    1. I totally understand your dilemma and we wanted to provide that feature. Laurie and I researched (and regularly check) for a printing plugin. None of the ones we found so far work on all platforms (windows, unix, android, iPhone, apple mac etc). Here are a couple options: (1) In many browsers you can right click and select print (2) cut the entire post and paste it into your favorite editor and print (3) use the specific browser print function.

  45. August, can you kind of put this in ‘plain English’ for us less tech savvy folks? Are these better than say, nicad batteries? longer life usage wise as well as recharge times wise? Are they more cost effective than other rechargeables? I don’t mind a larger up front cost if it is going to save me more money in the long run. DH uses rechargeable batteries for his work equipment (cheaper stuff, but company reimburses him) and if we can find something more cost effective, that would be great.

    1. Good questions and thank you for the kind words. 1st off I would not switch devices that use AA or AAA to 18650 unless it was an EVERY DAY use. I might use up the old AA or AAA batteries first before considering switching. Remember these are completely different sizes, and weights. But if you have a need for a very bright flashlight or a device that uses the 18650 go for it. They can be recharged and are readily available from dozens of manufacturers and are likely to only get better over time. As an example I would recommend the ThruNite TN12 or Fenix PD35 to a police officer hands down. It has more power so will last longer in use.

      Nicad (NiCD), Lithium ion, Nickel-Metal Hydride (NiMH),lithium polymer, alkaline and lead/sulfuric acid in a 12volt car battery — are all ways to store energy. Alkaline and straight lithium (like Energizer Ultimate) are NOT rechargeable. We like the non-rechargeable Energizer Ultimate (lithium) over the other alkaline batteries because they are much less likely to leak/corrode. Also the Energizer Ultimate has a 20 year shelf life, so is great for emergencies. Some of the rechargables have longer shelf life too. Again you need to compare the battery to your use. 18650’s are designed for use – not shelf storage.

      Are these better than say, nicad batteries? longer life usage wise as well as recharge times wise?
      Not Necessarily, you have to read the specs to confirm. Some of the extreme drain rechargeable batteries will only recharge 100 to 500 times where a more normal high drain could be recharged 2000 times. This matters if you use a device every single day. The AA will last longer for the same amount of light than AAA, and an 18650 will last even longer (see the table). The 18650 has 10x the wattage capacity as the lower end AAA and the 18650 is 3x to 4x the capacity of the AA.

      Are they more cost effective than other rechargeables?
      Again unless you have a need stick with AA or AAA rechargeable batteries. The Eneloop AA is a better buy if you don’t have a direct need. It can be recharged 2100 recharge cycles (2100 times). So it would last 4 to 5 years of recharging with every day recharging. Amazon has good rechargeables also, but they are almost the exact same price as the name brand Eneloop. Here is more info on our AA, AAA and chargers-

      Overall, we recommend any rechargeable including: car batteries, NiMH, NiCD and LiPo. The 18650 is rechargeable Lithium Ion. The only thing we recommend the Alkaline for are gifts or devices that are likely to get lost. Whether you are using AA, AAA, 9v, button or a car battery – match the battery to your needs. But note the Energizer Ultimate has more “capacity” than the normal 14500, but it cannot be recharged.

      We don’t recommend the alkaline AA/AAA batteries they are cheap. BUT an alkaline battery is way more expensive compared to rechargeable after only 2 to 5 recharges. They can be used in high-drain devices (high lumen LED flashlights, digital cameras etc) BUT their life expectancy will be sharply reduced. They also suffer from more temperature sensitivity. And in day to day experience they tend to corrode and fail more frequently.