Heating system for off-the-shelf LiFePO4 battery

[BilTheGalacticHero]

I'm setting up a heater for the LiFePO4 battery system I've built for my Jeep. The battery will be located inside the Jeep and surrounded by foam but we're often out in below freezing conditions and I need a heater so I can charge. This is the battery...



It has a thin ABS case. I got a four pack of 25W silicone sleeved heating pads of Amazon, the same as others have used...



I've been experimenting with two in series and they get to something like 130-140F just sitting on their own. If you put anything on them to absorb the heat (like even your hand) the surface temperature drops to around 100F. I was planning on using just the two pads. I've seen advice to stick them to the side of the battery or under the battery, either with or without an aluminum heat spreader. It appears some people are running four in a series-parallel configuration but that seems like a lot of heat. I'd really like to hear where people are placing these and how (and how many).

In another post I got advice just to tape the temperature sensor to the top of the battery case but I've been reading more threads here and see other people say to attach it to a battery terminal. I still can't decide what to do. The battery case is such thin plastic it really makes me wonder.

Looking forward to hearing (more) advice.

Thanks in advance!

 

[YurtSolar]

I'm setting up a heater for the LiFePO4 battery system I've built for my Jeep. The battery will be located inside the Jeep and surrounded by foam but we're often out in below freezing conditions and I need a heater so I can charge. This is the battery...

View attachment 181061

It has a thin ABS case. I got a four pack of 25W silicone sleeved heating pads of Amazon, the same as others have used...

View attachment 181062

I've been experimenting with two in series and they get to something like 130-140F just sitting on their own. If you put anything on them to absorb the heat (like even your hand) the surface temperature drops to around 100F. I was planning on using just the two pads. I've seen advice to stick them to the side of the battery or under the battery, either with or without an aluminum heat spreader. It appears some people are running four in a series-parallel configuration but that seems like a lot of heat. I'd really like to hear where people are placing these and how (and how many).

In another post I got advice just to tape the temperature sensor to the top of the battery case but I've been reading more threads here and see other people say to attach it to a battery terminal. I still can't decide what to do. The battery case is such thin plastic it really makes me wonder.

Looking forward to hearing (more) advice.

Thanks in advance!

I'm following this thread! Also searching for a good battery heater solution and considering these pads.

 

[davps12341234]

i use a PTL100w heater with included fan, i place it so it blows across the side of the battery, so far at 22f outside it maintains 40f using the temp probe from shunt thats bolted to neg side of battery,,, anyone see faults with my set up,,,,ptl is drawing power from battery if shorepower is not available

 

[Skypower]

If you can stuff some insulation around the battery you’ll use a lot less energy to heat it.

 

[Ralos]

Are you using this as a starter battery or to power the interior as a camper? I don't know if your battery cost was limited, but after the fact, why didn't you get a self heating battery? That being said, you need to watch Will's battery tear down videos on YT and you'll see in most of the batteries in those videos there's usually an air gap or space between the battery cells and the case. That air gap can act as an insulator not letting much of the heat reach the cells. Your idea of external heater pads on the case may work, if they don't get hot enough to melt the case first.

 

[suimei]

In my example, four 12.8V100A Lifepo4 batteries are kept warm by an 18W heater.
I heated the aluminum case because if I put the heater pads directly on the batteries there is a risk that the temperature would be too high. The result was good.

Where to place temperature sensor on enclosed LiFePO4 battery (for heater activation)?

The machine translation is excellent. Nice work and thanks for the experimental data.(y) I hope this will be of some help to the participants. I implemented it in my little camper and mission accomplished.

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