this is why

StirCrazy wrote:

valhalla360 wrote:

3 tons wrote:

SDcampowneroperator wrote:

LittleBill wrote:
this has been solved. they now sell bms's with heating options. When I make the switch they will be used in 0f unprotected temps.

Wont the heating option then use battery power?

No, the heating option is powered by the battery’s charging source.

3 tons

If there is a constant charging source, no need to mess about with a large battery bank...which is the primary reason to install lithium.

Of course, if there is a charging source, a small heating blanket negates the temperature issue of cold.

may not be shore power they are using to preheat the batteries, it might be solar. once the batteries are preheated there is no need to keep them warm as the furnace will be warming the space there in, if they are set up properly. all the BMS does is redirect the power it recives to heating pads or what not instead of the batteries untill the internal temp of the batteries is high enough for them to safely accept a charge. but people keep forgetting that you can discharge LFP batteries in most cases to -20C so in reality you could start the furnace and warm up the rv. If you have the batteries inside the heated space, this inturn would also warm up the batteries, and all you need to do is install a disconect on your solar panels that you can leave off untill they are warm. theres always ways around cold if your willing to look for them.

Steve

Pretty much, the bms's have a configuration for min temp for charge, pretty simple. the battery doesn't charge until the temperature goes up to a set point , at which point it stops heating and redirects the charge into the battery's themselves.

Also don't need a solar disconnect since its in front of the bms, bms will just use the solar to keep the battery's warm, no different than any other charge source.

OP's case is extreme, and shouldn't be considered for a normal use case. Still I would be confident I could keep them warm at -40, with an insulated box, and the heating pads I have looked at... Will it extend charge times? Yes... how much I don't know. But at -40, my generator is prolly running a lot. also how are you dealing with water and tanks? seems like that's a bigger issue to handle power wise, then the battery component.

I have camped so far to about 20F, and its prolly the coldest I'm going. I have single pain windows, and were easily the coldest component of the rv.

let the op buy his batteries. hope they work, for everyone else a heated bms, pretty much allows the lith's to sit outside unprotected. Which is where mine are going.

remember charge/vs use are different values. Most people are not camping below the use case scenario. and in my case. the bank will be so large. I prolly won't need to charge the entire time I am there.