Lithium heating pads
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
Forum Discussion
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).
