Lithium heating pads

[dennych1]

Has anyone added heat pads to your lithium batteries so you can charge below freezing. If you did what did you use and how did it work

[gatorcq]

Folks, my system works very well in 17 degrees F. The batteries are staying around 40. You be the judge, I can charge my batteries with no issues.
Oh I forgot to mention, my LB were $420 ea @100 Ahrs. Far cry from $1000 BB.

[phemens]

FWC wrote:
A couple of things to think about before adding heaters to your LiFePO4 batteries:

1. Are you really 'protecting' them? Many (most?) LiFePO4 batteries have a low temperature charge cut off built in to the BMS, so they protect themselves and won't accept a charge below a certain temperature (I think it is about -3C for Battleborn). The downside of not having a heater is that you may miss out on some charge opportunities when it is very cold, not that you will damage the batteries.

2. How much energy will heating the batteries use? Several of the solutions presented here keep the batteries MUCH warmer than they need to be. There is no advantage in heating the batteries to 20C and it wastes energy. You also only need the batteries to be heated when charging, they can be cold while discharging. It is far more (electrical) power efficient to heat your batteries with what ever heater you use to heat your living space - which I assume you keep above -3C.

3. There are situations where you really do need to heat the batteries - but they are less common than most folks think. In the case you do need heat then external heat pads are the best option. While internally heated batteries seem like a good idea, if you us a battery monitor to track things (eg a Victron BMV) the internal heaters will throw everything off as the current for the heaters cannot be accounted for by the monitor.

To your point 1) & 3), that's exactly why I have the heating pad, to permit charging in conditions where normally the BMS would prevent it. Admittedly for me this is in cases where it's marginal (i.e. the battery temp is already close to the cutoff @ 5-8 C according to my Victron battery temp sensor) but I never reached it. Better safe than sorry for me, having the capability to charge when I want was important to me - we leave our RV at a remote site off grid and keep the residential fridge running, so I need to ensure the batteries stay charged.

For point 2), the heating pad draws a steady 6 amps @ 12v. For me, since I have more than ample capacity, I don't worry about that too much, the solar tops batteries up usually before noon. Batteries are in the front compartment and it is not ducted for heat, and we rarely run the main heater, we prefer to use a Mr. Buddy to cut down on noise. (we only run it when we're up, not overnight).

[dennych1]

Using the tank heater pads can you actually feel the warmth when it’s on

[FWC]

A couple of things to think about before adding heaters to your LiFePO4 batteries:

1. Are you really 'protecting' them? Many (most?) LiFePO4 batteries have a low temperature charge cut off built in to the BMS, so they protect themselves and won't accept a charge below a certain temperature (I think it is about -3C for Battleborn). The downside of not having a heater is that you may miss out on some charge opportunities when it is very cold, not that you will damage the batteries.

2. How much energy will heating the batteries use? Several of the solutions presented here keep the batteries MUCH warmer than they need to be. There is no advantage in heating the batteries to 20C and it wastes energy. You also only need the batteries to be heated when charging, they can be cold while discharging. It is far more (electrical) power efficient to heat your batteries with what ever heater you use to heat your living space - which I assume you keep above -3C.

3. There are situations where you really do need to heat the batteries - but they are less common than most folks think. In the case you do need heat then external heat pads are the best option. While internally heated batteries seem like a good idea, if you us a battery monitor to track things (eg a Victron BMV) the internal heaters will throw everything off as the current for the heaters cannot be accounted for by the monitor.

[gatorcq]

I installed Universal Car Seat Heaters. There are 2 pairs, 1 for bottom, 1 for back.
Setup using a small T-stat controller (C degrees) less then $15 for 4 units.
Tied directly into the battery terminal (Fused).
Working very well in Toronto, On.
My LB are installed up front, next to the Generator. Used Foam board to insulate around the LB. Heaters underneath and behind.
T-stat turns on at 40 Degree F. Works very well right now. Batteries will stay up around 40 to 60 degrees.

[dennych1]

Thanks you have been very helpful

[phemens]

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.

[dennych1]

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

[phemens]

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.

[riah]

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.

[dennych1]

What tank heater did you use

[phemens]

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!)

[deltabravo]

BattleBorn heat pads

[phemens]

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.