Lithium heating pads

Yes. I have Battle Born LiFePO4 batteries and just used their thermostat-controlled heating pads. Not cheap, but very easy.

Rob

Someone I know used motorcycle or snowmobile grip heating pads.

I have. I added a waste tank heater stuck to a thin aluminum plate. That goes directly under my 6 LiFePO4 batteries. I also have a battery temperature probe attached to my Victron setup to prevent charging if the temp goes below 5C. Batteries are surrounded by foam board insulation.
I considered the grip heating pads, but the waste tank heater has the automatic temp kick in, so I went with that instead. Seems to work very well. It draws down roughly 6 amps per hr and comfortably kept the batteries 10 degrees above ambient. I didn't get a chance to measure under colder conditions as our season wrapped up first.

deltabravo wrote:
BattleBorn heat pads

Nice, but very expensive $220 for essentially what the waste tank heater does at 1/5 the price (I guess you'd need one of the Battleborn heaters for each battery, for me that would cost over $1200!)

What tank heater did you use

Any pictures of your set up? Also, what waste tank heater model is it? An Auto temp kick in sounds great! Tia!

phemens wrote:
I have. I added a waste tank heater stuck to a thin aluminum plate. That goes directly under my 6 LiFePO4 batteries. I also have a battery temperature probe attached to my Victron setup to prevent charging if the temp goes below 5C. Batteries are surrounded by foam board insulation.
I considered the grip heating pads, but the waste tank heater has the automatic temp kick in, so I went with that instead. Seems to work very well. It draws down roughly 6 amps per hr and comfortably kept the batteries 10 degrees above ambient. I didn't get a chance to measure under colder conditions as our season wrapped up first.

Here is the heater I purchased from Amazon (it's more $$ in Canada): Link
It goes on automatically at roughly 7C and shuts off at 20C.

Attached it to some stock sheet aluminum to spread the heat across all 6 batteries. Added a cut-off switch for when I don't need it.

Also use a Victron temperature sensor connected to my Victron MPPTs to ensure that the solar won't charge the batteries is they go below 5C.

My battery is 10.5x20 you think I can stick the pad right to the bottom and do you think I would have to enclose battery. It’s great to converse with someone that has done this

dennych1 wrote:
My battery is 10.5x20 you think I can stick the pad right to the bottom and do you think I would have to enclose battery. It’s great to converse with someone that has done this

I think if you centered it you'd be fine. My footprint is considerably wider and it does fine with the aluminum sheet. As far as enclosing the battery, it depends on where it is located and to what temp you expect to use it. The heating mat can reliably keep the battery temp a minimum of 10C above ambient (at least from what I've observed in limited testing so far). I use foam insulation because they're located in the front storage compartment that has openings for the landing gear and gets quite cold. The batteries have considerable thermal mass, so it shouldn't take much to keep them in the acceptable temp zone with the heated pad. I'm probably veering on the other extreme of precautions, but I want to protect my investment.
I think a good temperature sensor on the batteries is a must for this.