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Build your own RV Lithium Battery Heater

Updated: Dec 27, 2022

Leisure-Lee February 2021

I have been a dedicated Battle Born Battery dealer for 6 years, and absolutely love the batteries and the company. Recently, Battle Born began offering their 100AH battery with a really nice internal heater.

This is particularly interesting to me, since I live in Colorado and many of my customers do cold weather camping. LiFePO4 batteries don’t really like to be charged below 32F, and Battle Born has built into their standard BMS (Battery Monitor System) a fail safe where the battery will still give you a full charge down to about -10F, but will not allow the battery to charge below 32F.

MortonsOnTheMove and Battle Born did a great study on cold weather battery performance of LiFePO4 vs lead acid here.

I designed a battery heater remote control based on a great bluetooth battery monitor system here.

Battle Born has sold 10’s of thousands of batteries prior to introducing the internal battery heater, and I’ve been building my own RV lithium battery heaters for my customers and friends for several years. After several iterations, I’ve come up with a low cost method that many DIY’ers could use to build their own battery heater.

Pro’s and Con’s of buying the Battle Born Heated battery vs. Building your own heater.


  • Battle Born is an excellent engineering company and has a great heater

  • It is backed by the full 10 year warranty

  • It is very easy to install, and works well on every battery in a multi-battery system

  • An internal heater is inherently more efficient than an external heater


  • It costs an extra $150 per battery (on top of an already expensive battery, and well worth every penny)

  • It doesn’t help you if you already own Battle Born Batteries without the heater!

  • You can’t buy it from your local dealer (like me!), you must buy direct.

  • It works internally, which means your external battery State-Of-Charge (SOC) meter is inaccurate

Here is an example of Battle Born’s great engineering skill. If you happen to pull your battery so low that the internal BMS (Battery-Monitor-System) Low Voltage Cutoff (LCO) activates, the battery will shut itself off. That is a great feature, it saves the life of the battery! Imagine you are cold weather camping, and forget to check your battery SOC (State-Of-Charge) or RTR (Run-Time-Remaining) because your don’t have a good Battery Monitor on the system. I can assure you that every one of my customers has a good Battery Monitor on their RV, its my number one recommendation for upgrades to an RV!

So you happily go to bed, and your RV furnace runs your battery down until it shuts off. You wake up at sunrise to a very cold RV. The Battle Born battery heater will apply whatever solar power you have to heat the batteries until they are warm enough to safely charge! This is a great design feature! Unless you have a cheap Chinese charge controller, which won’t even turn on unless it detects a minimum voltage of 9V. Read my blog on which charge controller are good to “wake up” lithium batteries.

So the Battle Born heaters are a good solution. However, I’ve been building LiFePO4 heaters for years, and have a really good, low cost upgrade for non-heated batteries. Basically, there are a few keys to LiFePO4 battery heaters:

1) A good LiFePO4 heater MUST NOT overheat the batteries. All standard truck battery heaters will do that. Don’t use a standard truck battery heater.

2) It must not provide to much heat. So lower power is better. I’ve found 70W is the max, unless you live in Canada (or Alaska or North Dakota!)

3) It should only heat the batteries to a maximum temperature of about 45F. 45F is the about the maximum you should heat lithium to for maximum life and efficiency.

4) Lithium battery heaters only need to work when there is a charging source. If you are on solar, that is 9AM to 4PM. No need to heat at night, or on cloudy days.

After several design iterations, all field tested, I’ve come up with a darn good LiFePO4 heater at a reasonable price.

I use 12/24V RV tank heaters, with a custom temperature control device that limits the heater temperature to 35F-45F. I use the built-in tank heater temperature control as a fail safe to limit the temperature to 65F. My controller uses a pulse heat control to help limit the power. Since it is an external heater, I also have the advantage that I can measure the actual battery draw, which means my external bluetooth battery monitor is always accurate.

At Leisure Solar, we love great American products like the Battle Born Heated battery, but we also always support the great American tradition of DIY. Call or email to chat more about this.


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