cold weather charge Lithium iron phosphate battery

[richxd87]

RELiON makes a "Low Temp" Battery with safe charging down to -4F. Is it worth the additional cost?

https://relionbattery.com/low-temperature-series-line

 

[Stan0]

Thanks to all for the valuable info.

 

[scandy]

I ran into this problem a couple nights over the winter with my battleborn battery. I had my diesel heater running all night which kept my interior pretty warm, but my battery, while being inside is in a spot next to my sliding door that still gets very cold. Some nights in the -20s, even though it was 50ish inside. The battery would have a good charge but I think the battery monitor that comes on the battery would shut it off.

Bought some hand warmers I could stuff next to the battery just Incase.

I looked at those heater pads. What I’d really like to do is figure out a temperature activated power switch, that would turn on a heat pad at 35 degrees or so and off at a slightly higher temp. I found some that looked like they could work but the temps for turning on/off weren’t what I wanted and the real deal breaker was that they were all 120v

 

[Hillbilly Heaven]

Links are just a few post prior. I posted link to what I thought to be favorable to control the heating pad. Those thermostats I post should work fine with DC voltages.
If you want an economical heater try universal seat heaters. Use just the heating pad and the above tstat.

 

[dwh]

There are a bazillion different snap-disk thermostats. Tons are used in HVAC and are usually 24v. The one I posted clearly states:

"Models with operating temperature ranges from -45C to +425C" (first bullet point)

This other page says:

"These robust thermostat switches can be used in high current applications; carrying up to 25 amps at 240VAC, for over 100,000 cycles (30 Amps at 12VDC for 30,000 cycles)."

http://senasys.com/automatic-reset-thermostat-options


Shouldn't be too tough to find one normally ooen that closes at 35F and opens at 45F.

 

[richxd87]

Heat stress is just as bad as cold stress for Lithium

Make sure there is an air gap between the heat source and the batteries.

@Alloy any idea what a safe contact temperature might be for LFP batteries if using something like the Kats 12v heater or Universal seat heaters?

Kat's Heaters Oil or Transmission Pan Heating Pad - 5" x 5" - 12V - 75 Watts Kats Heat

Place this heating pad under your oil or transmission pan to keep the fluid from thickening in the winter. Warm fluids lubricate better for a long-las

www.etrailer.com

Amazon.com: Dorman 628-040 Universal Seat Heater Kit: Automotive

Buy Dorman 628-040 Universal Seat Heater Kit: Accessories - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

DC Battery Heater Kit FM316 by GTO ? NOT SOLAR COMPATIBLE

Keep your GTO gate opener running smoothly with the DC Battery Heater Kit FM316. This battery warmer is essential for cold climates and is not solar compatible. Order yours today.

www.northshorecommercialdoor.com

 

[DaveInDenver]

You could probably just tell from the data sheet. For example a randomly selected 1868130 has a max charging temperature of +45°C and max discharging temp of +60°C.

http://cebabattery.com/wp-content/uploads/2018/01/LiFePO4-1868130-3.2V-10Ah-Battery_DATASHEET.pdf

So depends on how they are enclosed and the thermal resistance between the case and batteries. If your proposed heating pad never exceeded +45°C at the battery then seems like it should be safe. I'd personally be careful about keeping the battery temp under control, though. Boom!

One thing to consider is a pad like that is the least efficient way to heat batteries since it'll end up with a wide gradient from contact point to the opposite side. The thermal management systems take great care to equalize, so they enclose the air space around them and use fans to circulate warm air or have liquid jackets around the cells. I'd be thinking a heater on maybe an aluminum plate or old heat sink from an amplifier and circulate warm air inside a battery box.

 

[Hillbilly Heaven]

That silicone pad mounted to copper plate will to do wonders for making a radiant heat source.

 

[shade]

Your still welcome to pull load off your battery if its below freezing, just not charge it.. if I kick my 1200VA inverter on and boil some water the battery would likely warm up enough that it could start taking a charge afterwords.

My LFP sat in my camper all winter @ 40% SOC with charger/loads disconnected, no need to take it out.. it should be fine in that state.

Seems like cycling a load on a timer or thermostat (probe at battery) and insulating the battery would be the simplest & safest way to warm it up for charging. That would also allow the battery to somewhat manage the temperature with its on-board system, rather than relying on external heaters & timers that can't communicate with the battery.

I'm surprised battery manufacturers don't sell warming blankets that can be controlled by the battery's management system.

 

[dreadlocks]

ding ding ding, its completely safe to pull load out of a LFP below freezing.. and it dont have to be much of a load and it'll warm the battery up on its own.

for example, I set my BMV high temp alarm @ 120F.. if I run my Microwave for about 5mins it'll jump from ambient to 120F before the microwave is done.. thats like +40F warming in a few mins w/load.. if my LFP was sitting at 10F, it'd take me just a few mins to get it warm enough to take a charge.. and who cares if I burn a few AH out of it, its about to be hooked to a charge source.. unless I'm at like 5% SOC its not gonna be a problem..

If you dont have a big power draw you can use, like an inverter.. just get a dummy load and hook it up.. It'll take longer to dig out the load, open the battery box and hook it up than it'd take for it to warm you up to safe charge temps.

 

[DaveInDenver]

Seems like cycling a load on a timer or thermostat (probe at battery) and insulating the battery would be the simplest & safest way to warm it up for charging. That would also allow the battery to somewhat manage the temperature with its on-board system, rather than relying on external heaters & timers that can't communicate with the battery.

I'm surprised battery manufacturers don't sell warming blankets that can be controlled by the battery's management system.

What you're talking about is implicit in the battery thermal management algorithms for EVs and stand-by systems. The reason I suspect it's not a standard feature here is it does consume quite a bit of energy and it's not really critical if all you're doing is discharging. In an EV the batteries have to be prepared to accept a charge pretty quickly because of regeneration or that perhaps you might at any time plug in or drive straight to a charging station. If you are fully in control of the both charge and load then manually starting a battery warming or just relying on discharging before charging is fine and doesn't waste energy unnecessarily. Tesla or whomever had to assume you have parked your car outside all night and warming 7,000 cells from their design limit of -30°F to +32°F takes a lot of time, so they have to balance not letting the pack get too cold against how much range it consumes in a parked shut-down state. If you're using a lithium battery to run your RV house you might or might not need to burn whatever, say 20 watts, constantly overnight if you know first thing in the morning you're going to turn on lights and make coffee before the solar kicks in.

 

[richxd87]

Thanks for the responses fellas, lots of good information!

 

[luthj]

You can treat the resistive heating pads as plain resistors. Putting them in series, reducing or increasing voltage to adjust output power. (consult ohms law). The thermostat should be placed in a location that will respond quickly to changes in case temperature. This will prevent spot overheating.

You should put an insulating box/blanket around the battery during the winter. This dramatically reduces the power needed to keep the pack warm.

There are numerous digital 12v temp controllers on the web/amazon. They have adjustable hysteresis, built-in relays, and a handy display. Some can also control and heating or cooling relay, so you could use such a controller to vent an enclosure in hot weather.