cold weather charge Lithium iron phosphate battery

[Stan0]

So in reading about lithium bat after buying one, I found out that you can't charge it under 32 deg. without possibly damaging it. We don't plan on doing too much of the extreme off roading but if we did get caught I am wondering if my mppt controller would adjust for this condition because it has a temp gauge option on it.
Anyone have knowledge on this subject? thanks.
S

 

[trailscape]

Unless it's specific about lithium batteries, the sensor is probably only going to compensate for voltage variances that occur with temperature changes. It's likely more designed to prevent over/under charging. Also, the sensor will only work properly if it's in the same location as the battery.

 

[dreadlocks]

Victron SmartSolar will stop charging in its lithium profile when it gets near freezing based upon external temp input from either a BMV or their dedicated BT temp monitor.. Ive tested and confirmed this behavior.

 

[Stan0]

WhIch MPPT do you have ?
I expect if it has that feature it will be claimed in its document.
Does your BMS otherwise monitor temperature and cut off if outside safe limits ?

rover Li 40 Amp MPPT .... upon further review it says I can't use temp gauge feature with lithium.... also a little confused about equalization.

 

[dwh]

Temp compensation for lead-acid batteries raises the bulk/absorb/float voltage setpoints as temp goes down and lowers the voltage settings as temp goes up.

Not a good idea to apply even higher voltage to an ice-cold lithium that isn't supposed to getting charged in the first place.


Equalization for lead-acid batteries is "a timed, controlled overcharge" to stir up the chemistry and break loose some lead-sulfate from the plates.

Not a good idea to use that function on a lithium.

(Note: Marketing departments are mostly liars, so there are quite a few chargers that have what they call "equalization", but don't actually do "a timed, controlled overcharge".)

 

[Stan0]

Temp compensation for lead-acid batteries raises the bulk/absorb/float voltage setpoints as temp goes down and lowers the voltage settings as temp goes up.

Not a good idea to apply even higher voltage to an ice-cold lithium that isn't supposed to getting charged in the first place.


Equalization for lead-acid batteries is "a timed, controlled overcharge" to stir up the chemistry and break loose some lead-sulfate from the plates.

Not a good idea to use that function on a lithium.

(Note: Marketing departments are mostly liars, so there are quite a few chargers that have what they call "equalization", but don't actually do "a timed, controlled overcharge".)

Much obliged , even further instruction manual/ app examination reveals that the rover 40A does not provide any time for an equalization period on a lithium bat. Encouraging in that respect. For now we will limit our camping to above freezing but monitor battery closely during sneaky cold fronts.

 

[Neil]

Don't know the exact details but some German friends of ours had a 6000 euro lithium battery bank in their truck. They picked it up from storage in the winter to discover that the battery bank and charger had shut down. It wasn't easy to get the ambient temperature back up to a charging level without power. They were seriously un impressed.

Neil

 

[Stan0]

yes that is an issue and I would be bummed too. The controller/ charger must have software/capability to deal with the shutdown feature on a lithium. It is reccomended battery is to be stored inside at a normal to cool but not cold temp. I will be taking ours out at end of our camping season well before that could be a problem. (hopefully) Good news is it's only 28lbs!

 

[dreadlocks]

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.

 

[Stan0]

Is it possible to use/wrap some sort of powered thermal warming pad around the battery safely for extenuating circumstances?

 

[dreadlocks]

yeah probably, I have an old rugged laptop designed to operate in artic temps.. the old mechanical hdd had a lil electric blanket thing that just burned energy to keep the bearing from freezing.. I threw it in the trash because battery runtime was already garbage heh.

but at that point just run a dummy load, seriously I can watch my battery temp sky rocket fast when I run my microwave.. You've got a Flyer right? I put my Propex furnace in same area as battery and put a passive intake vent right next to battery.. Ive been out plenty of sub-freezing nights camping so far and with furnace circulating air in battery compartment it's never been in danger of freezing.. battery is 70F like rest of the trailer.. in the winter when I'd go out there and work on my trailer or just hide from the family it was pretty easy to warm up the battery when I wanted.

 

[Jocke]

You can get heater pads for terrariums (reptile tanks) and such. Get one of those and stick it under the battery, keep the battery in an insulated box. If it drops below 0ºC use the pad to heat it up so the battery can take charge, then at below -20ºC you need to stop draining power from it. Check your battery manufacturer for details. A system to monitor this could easily (relative term, right?) be built using an Arduino and some sensors and some relays.

 

[dwh]

https://www.etrailer.com/Vehicle-Heaters/Kats-Heaters/KH23075.html

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https://www.comstatinc.com/thermostats/snap-disk

 

[Alloy]

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.

 

[Hillbilly Heaven]

https://www.etrailer.com/Vehicle-Heaters/Kats-Heaters/KH23075.html
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https://www.comstatinc.com/thermostats/snap-disk

I can testify to those heaters. We use the 120 volt version of them at work to warm engine oil.

I use these snap disc thermostats to control fans when heat sink temps rise on electronics. They are opposite action of what is needed for heating purposes.
You need open on temp rise and auto reset. I would think anything from 50-75 degree F would be perfect.
https://www.comstatinc.com/thermostats/snap-disk/auto-reset-c-1_2_3-l-en.html