The Battery Powered Heater – Mythical Heating System
There are thousands of online searches each month for “battery operated heaters” and “battery powered heaters”. A cordless heater that runs on a couple batteries that we can easily swap and recharge would be handy. Very small individual battery powered heaters for gloves or boots do exist. The bad news: A large portable battery powered space heater does not exist.
Good News: There are some options available you might not know about. You can buy safe indoor propane heaters.
If battery technology advances enough, it is possible a battery powered space heater might exist in the future. We will update this post if technology changes.
Safe Indoor Space Heaters
There are a number of safe indoor propane heaters. Both of the units below are California compliant. If you stock a number of the propane tanks or have a larger external one you can provide relatively safe emergency backup heat.
**Whole home heaters vary from 50,000 BTU to 200,000 BTU (and vary with house size and local climate)
Other Emergency Indoor Heating Options
Consider a wood burning stove and install it with proper ventilation. Consider adding insulation and other improvements that reduce your heat loss. Related posts include: 25 Cheap Ways to Keep Your House Warm in Winter and Best Ways to Keep Your House Warm – New Construction and Remodeling Tips and if you have the time and skills a rocket stove is another option that requires construction.
If you have natural gas utility as an option, you might consider a unit such as the Mr. Heater 30,000 BTU Natural Gas Blue Flame Vent Free Heater – but it requires natural gas feed installation. Remember in large storms and hurricanes natural gas may not continue to be available.
For more information on general house heating see https://smarterhouse.org/heating-systems/types-heating-systems
What about the risks?
Using a propane heater, even a safe one does have risks such as: fire, carbon dioxide and carbon monoxide. But for these safer units the other risk you might not know about is water vapor. A propane burner that has a correct burn, creates mostly water and CO2. That is how the ultra efficient safer units got California compliance. The extra water vapor can be an issue if the unit is run for an extended period.
Fire: The highly efficient indoor propane units are designed with shields, but they is still a risk of fire. Similar to a plug in electrical heater. Never place flammable objects near a heat source, especially a propane heater, unless your unit indicates otherwise. Some portable propane heaters do allow flammable materials on the back side of the unit, such as the cabinet mounted Big Buddy shown below.
CO2: Nearly all the safe indoor propane heaters have oxygen sensors so they will shut off automatically if they detect too little oxygen. If your home is very tight you may need to crack a window to allow carbon dioxide and carbon monoxide to escape and oxygen to enter the area, especially for small areas less than 20 x 20 ft. More information on the exhaust from an indoor propane heater.
Water: Using a safe propane heater indoors can create a lot of water vapor. You may have issues with moisture on windows (condensation) if you use a propane heater in the winter (low humidity).
If you do decide to get an indoor propane heater, consider a carbon monoxide detector just to be safe. If you are really worried you can also purchase a carbon monoxide and carbon dioxide detector which is more expensive but detects both CO2 and CO.
You must have a fire extinguisher in your home or apartment and one in your utility area if you have a larger home. Even if you don't purchase a propane heater, or a wood stove, you need a fire extinguisher.
Questions and Answers About Batteries and Heaters
How does a 12 volt heater in a car work?
It actually isn't a heater. It is a fan that blows air past a coil with hot coolant from the engine. The air is blow past a coil. The air cools the coil (while it warms the air – heat transfer). So the heater is a combination of a fan and the gas or diesel coolant system.
Don't some cars have 12 volt heaters?
Yes, you can purchase 12 volt resistance heaters that create about 150 watts of heat and draw about 20 amps (so it needs a 20amp fuse). A 150 watt heater creates about 500 BTU per hour (a home system creates 40,000 to 200,000 BTU). So the little 20 amp heater is not going to heat a house, but it will still drain a 12 volt car battery dead very quickly.
Electric cars also use a 12 volt resistance heater. The electric car 12 volt resistance heaters use a LOT of electricity, and in electric cars, this quickly results in the backup gas engine being engaged or the car needing a charge quickly.
How Does a battery create heat?
It is basically electric resistance heating, which uses a lot of current (electricity) to create the heat. The battery goes through a high resistance coil (heating element) and it resists the electrical flow and heats up. This uses a lot of electrical power or current. A home normally needs 40,000 to 150,000 BTU. A small car battery heater creates 500 BTU at 12 volts 20amps – so you would need 100 to 500 car batteries to heat a home with electricity for any extended period of time. Its not currently practical to use batteries to power resistance based heat systems.
Can't I get any heat from a battery?
Yes, there are small Battery Powered Hand and Foot Warmers such as the Autocastle rechargeable heated gloves. These type of gloves generally use expensive high wattage LIPO batteries and still only last a few hours. A better alternative for emergency use is chemical hand warmers, such as HotHands Hard Warmers. You can get 8 pair of HotHands Warmers for under 10 bucks, and each set of warmers provides up to ten hours of heat. (Reviewers commented that they've had them stay warm from around 3 hours to 12 hours, depending on conditions.) The chemical hand warmers are far more effective, but they are one time use.
What does exist?
You can purchase battery heated clothing such as Lithium or Li-Po powered jackets, gloves, socks, and even battery powered blankets. Battery powered, heated clothing is available from Dewalt, Bosch, Makita & Milwaukee and many other providers. The only thing we personally have experience with are the heated gloves and vest, that grandpa uses, he appreciates the extra heat.
- Cordless Heated Jacket
The only thing that comes close to a battery powered heater is a unit such as the “Portable Tent Heater” sold on Amazon. This unit likely uses an automotive 12 volt car electric resistance heater. A 12 volt DC resistance heater is normally intended for use while a car is running (generating 12 volt electricity). We don't recommend it.
There are numerous 12v corded blankets and small heaters for your car. However these obviously aren't directly battery powered, and are dependent on the alternator more than than the 12 volt battery.
Could I use a car 12 volt resistance heater?
The small car 12 volt resistance heaters use an 12 volt alternator for power, not the car battery. The alternator is powered by a the gas or diesel engine. It creates about 100 amps of power while the engine is running (the 150 watt 20 amp heaters use up 1/5th of that power).
The alternator charges the battery and runs the electronics in the car, including the 12 volt resistance electric heater. A single automotive 12 volt battery can't power a 12 volt heater for very long without being drained completely. It can be drained so much that it will damage the battery. If you are not careful setting up the power for a heater that uses 12 volt car batteries, it can easily cause a fire. So you might be avoiding propane to avoid fire, but any resistance based heating can also cause a fire.
A safe 12 volt heating system would require multiple 12 volt car batteries. Portable battery powered heating is not practical. You'd need to recharge all the batteries every day, which would be a challenge, as the batteries would drain faster than they charge. It would require overdraw protection and fuses or breakers to protect from excessive amperage draw. Further the amount of electricity needed to create space heating is significant. That is why whole house electric heaters or electric stoves are expensive to operate, they draw a lot of electricity.
To heat a 1200 square foot home would require dozens of 12 volt car batteries. So as we noted, there is is no such thing as a battery operated space heater. If you see one advertised, it is probably a scam or mislabeled product search result.
More Winter Preparedness Posts
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