Charging LFP vs Temp ?

BFL13 wrote:
I see Trilliums specify that you must use fewer amps initial charging rate as temperatures cool. Are all the LFPs like that? If so, that means it is not just below freezing they have a temperature issue.

https://www.trojanbattery.com/pdf/datasheets/27_Lithium_12.8-110.pdf

As a rule they are. I don't do a lot of camping in subfreezing weather so I am not too concerned about that but I will probably put in a battery heater if I go with LiFe batteries.

I have found some batteries that come equipped for cold weather.

Chins cold weather battery

Yes the low temperature charging at lower speed is normal for lithium. Too fast and the metallic lithium separates in the battery. BMS should control this but need to verify. Best to keep them warmer.

It is all about scenarios as usual. That jump from 15 to 56 amps at 41F can't be right. Must be a sliding scale?

Camping up-Island off-grid in provincial park in Dec, Jan, Feb, it is usually around 35F when doing the two hour gen time from 9-11am.

15 amps limit per 111AH. No tapering with LFP so you get to restore 30AH in the two hours per 111AH of bank. Using 150AH or so per day.

You would need two of those batts for one day, but how to recharge them at 60AH for two hours gen time? If you use the two hour evening gen time after dark (no thanks) that would total 120AH.

As is at 35F, I can restore 184AH as a "50-90" in just over two hours with my four 6s and 75 amper. (I cheat a little on the two hour limit--don't tell anybody)

So wait till March? Now you can use proper 56 amps above 41F so you can do 112AH in an hour with two batts if you have a 112 amp charger (and a 3000w gen--not impossible--we used to have that with the 5er) or take two hours with the 55 amp converter and a 2000w gen.

So no good for our winter scenario and it is not even down to freezing.

How about those LFP heating pads people buy to keep them above freezing?
Just how warm do they get the battery when ambient is 32F? Does it get them above 41F so you can charge at a decent amps rate or just get them a little above freezing? Nobody has mentioned that AFAIK.

My lfp batteries are in the front compartment of the 5th wheel with no heating pads on them. The compartment has had foam insulation added on the walls where possible and did tap into the end of the heat duct in the compartment but it doesn't add awhole lot. With nighttime lows in below freezing, early morning till 9:30 outside temps 25f, daytime getting to low 40s and the cells will stay at roughly 42f and compartment 47f. Still using the batteries like any other day.

Now when the temp hits 10f outside with 25f as the highs, that's when I have to throw my little electric heater in the compartment for an hour to blast the chill out of there. The cells will start to slowly creep towards 32f. The batteries sit on a 1/2" thick rubber mat but the sits on the metal floor of the compartment which work like a large heat sink sucking all warm from the cells at those temps.