Heating pad for LiFePO4 (Lithium) batteries in your aircraft

[Neal]

I love my EarthX battery and I live in VA so really don't need to worry about extreme cold conditions, however, it has been an unusually cold December with temps below 32 almost every night, typically teens or 20's. LiFePO4 batteries can discharge at a wide temperature range but can only be charged typically in a narrower range such as the bottom side being 32F. So what do you do when you live in a cold climate where you may remain below 32F for extended periods of time?

LiFePO4 batteries typically have an internal battery management system (BMS) or an external BMS such as in my motorhome (RV) as pictured below. The company that installed it has a person that custom makes 12V heating pads that wrap the compartment and is controlled by a temp sensor (Ruuvi bluetooth device) and connects to a Victron device that can sense the temps and turn on/off a relay that controls the heating pads. Not an option to be this elaborate in an aircraft typically but with EarthX etc. on the rise in adoption, heat needs to be part of the solution. The BMS will prevent damaging the battery (hopefully) by preventing charging when the temps are out of limits. There has been discussion that the optimate charger is temperature aware, I have not personally read that and I'm not sure if it does or not, the battery typically controls via the BMS whether it can take a charge or not. The charger and battery may be different temperatures so I personally would not want the charger doing the decision making, the battery (BMS) needs to do that.

Knowing EarthX has a temperature bottom limit that I may go below here in VA I did wrap my battery in a battery insulation I found on Amazon that cars may use in colder climates. In hindsight I wish I didn't as it made things harder to install but it does add a cushion as the EarthX does need vibration protection and they include foam pads for you to use. If installing an EarthX consider good vibration dampening as I believe it's protecting the BMS and electronics within from vibration damage.

So how can you handle this temperature issue? If I lived in a cold climate like Siberia Minnesota or Alaska I would find a 12V heating pad and control it by a rocker switch which is easy to install. You'd need to fabricate some type of mount for it. But there is no reason the EarthX itself can't power its own heater, again, it can discharge below freezing, it just can't be charged. So if you can get the temp up on it then it will take a charge. I did a quick search for 12V heating pads for LiFePO4 batteries and there are options out there. There are also 120V options where you could just plug one in like your engine pre-heater. Just think through the scenarios of when/where you may need heat and ensure you have the ability to heat the battery while away. Fortunately my plane (FX-3) has good heat but if you are flying in a situation where you can't get the inside of the airplane above freezing then it's not going to charge even while in flight which is not a good thing, you need a heating solution to resolve this problem. Ideally EarthX should offer a battery with an internal heater like other brands offer. Nag them to make it happen and I haven't checked to see if they offer anything yet, maybe they have an answer to the problem but I'd reach out to them. When I inquired about this problem a year or so ago they said starting the airplane will generate heat within the battery. I personally don't agree with this as a solution to this problem.

For those that create a solution to this problem, please share for others to learn from.

Here is the 12V rocker switch I use in my RV, simple to install and control an on/off situation such as this manually.

Amazon.com

Here is the heating pad used in my RV (road type) setup.

 

[Cubonaut875]

I was actually thinking about this: TAHP3094-500 - Tanis Aircraft Products My G5 seems to act up in the cold also, it does not seem to start up when it is cold. It is an item I am watching. I am pretty sure I read in the optimate manual that it will not charge outside of the temp parameters, I might be dreaming, but I'll give it a look later in the day.

 

[Neal]

CORRECTION: I did a little digging and if you click on the Specifications tab at this link it shows the info below. Looks like charging stops at -40F! This is odd as your LiFePO4 battery charge below 32F will damage the battery.

 

[Neal]

I reviewed the manual and it does not address temps for charging (attached) and seems like an intentional omission as LiFePO4 batteries have temp limits for charging vs. storage and discharge (aka use). The good news though is the optimate charger and the battery align in their temp window. Whether you/I believe that it can be charged at -30C is another story. Here is the email dialog I had when asked about this, about 3-4 replies into the conversation where I pointed out the specs address use and storage and NOT charging.

 

[Cubonaut875]

As with most things, a straight answer is difficult to get. I do remember reading that the optimate charger would not charge below freezing rendering it almost useless unless running the avionics on the ground for extended periods of time, but I was in such a habit from my other plane attaching the battery sustainer after each flight that it seemed kind of odd not to do it for the new plane. I just came back from the hangar on a crappy no flying day and was sitting down to peruse the manual, thanks for doing the research!

Btw - I put my charger on a $6.00 step stool from Harbor Freight in case the charger melts it only takes out the stool. It's also great for the less limber and athletic to get in the back seat and it folds flat and fits in the back of the plane so the less limber and athletic can exit the plane when it's time to deplane.