why i call Li fussy

itinerant1,

Below about -20 c condensation because not much of an issue where I live. I've even sometimes used a humidifier. (but rarely).

time2roll I've taken special measures with the water system, so it is not an issue for me. The worst problem is finding a place to dump. The only local campground open in winter now wants $20 for a dump. I do have thermostatic control of the waste tanks--and the fresh water is inside the heated area.

BFL13 wrote:


No info to compare different heating methods and "size" of heaters, but one of the low temp LFPs that uses the charger to heat it up first before charging starts has this info :

"Because it takes time to heat the cells, the charging process in below freezing temperatures will take a little longer. For example, with the low-temperature RELiON RB100-LT 100Ah battery, it takes about an hour to warm from -20°C to +5°C before charging begins. Over a smaller temperature range, heating to a safe charging temperature happens proportionately faster."

https://relionbattery.com/blog/lithium-battery-cold-weather

That seems consistent with relion using a 100W heater for their battery. Based on the assumptions above 125W will get you ~30C temperature rise, 100W should get you about 25C temperature rise.

It also demonstrates the point that heating the batteries is fast - an hour is reasonable, or maybe 2 hours if you have a less wattage available.

FWC wrote:
The other thing to note, is that it really doesn't take that long or that much energy to heat the batteries.

The heat capacity of LiFePO4 is about 1000 J/KG/C meaning 1000 Joules of energy will raise the temperature of 1kg of battery 1C. A 100Ah LiFePO4 is about 15Kg, so to raise each battery 30C you would need 1000*15*30 = 450,000J. One Wh is 3,600J, so it would take 125Wh (ie 125W for an hour) to raise the temperature of the battery 30C.

Now that is per battery, but assume a decent sized bank of 600Ah, that is still only 750Wh. That is a standard electric space heater on low for 1 hour. Or it is 30A from your alternator for 2 hours. Or just using each battery to heat itself, it is only 15% of the battery capacity. Compared to heating the several tonnes of the RV up, this is trivial.

No info to compare different heating methods and "size" of heaters, but one of the low temp LFPs that uses the charger to heat it up first before charging starts has this info :

"Because it takes time to heat the cells, the charging process in below freezing temperatures will take a little longer. For example, with the low-temperature RELiON RB100-LT 100Ah battery, it takes about an hour to warm from -20°C to +5°C before charging begins. Over a smaller temperature range, heating to a safe charging temperature happens proportionately faster."

https://relionbattery.com/blog/lithium-battery-cold-weather

With all those extreme limiters in mind, sounds like a lifestyle change may be in order??…Either way, it would seem that extended periods at -30 degs does help to rationalize your inclination towards Sio2 (this,
supposing they’ll do the job adequately?)…FWIW, I view this as an outlier scenario…

3 tons

Itinerant1 wrote:
I couldn't imagine the condensation from extreme cold to warming temps inside the trailer.

I'd be buying propane every 3 days.

The other thing to note, is that it really doesn't take that long or that much energy to heat the batteries.

The heat capacity of LiFePO4 is about 1000 J/KG/C meaning 1000 Joules of energy will raise the temperature of 1kg of battery 1C. A 100Ah LiFePO4 is about 15Kg, so to raise each battery 30C you would need 1000*15*30 = 450,000J. One Wh is 3,600J, so it would take 125Wh (ie 125W for an hour) to raise the temperature of the battery 30C.

Now that is per battery, but assume a decent sized bank of 600Ah, that is still only 750Wh. That is a standard electric space heater on low for 1 hour. Or it is 30A from your alternator for 2 hours. Or just using each battery to heat itself, it is only 15% of the battery capacity. Compared to heating the several tonnes of the RV up, this is trivial.

I couldn't imagine the condensation from extreme cold to warming temps inside the trailer.

time2roll wrote:
Takes my fridge a solid 12 hours to get cold even in mild conditions.
Can't imagine hopping in a -30 cold soaked RV and instantly expecting everything to work normal. How long would you run the furnace before you rolled out? Water system might need more preparation than the LFP.
Just about everything is fussy at -30.

This is why I don't understand this use scenario. The batteries are only one of many things that are going to be problematic at -30C. Assuming you left them at least partly charged, there is no real hurry to heat the batteries, they only need to be (relatively) warm before you charge them.

Takes my fridge a solid 12 hours to get cold even in mild conditions.
Can't imagine hopping in a -30 cold soaked RV and instantly expecting everything to work normal. How long would you run the furnace before you rolled out? Water system might need more preparation than the LFP.
Just about everything is fussy at -30.

3 tons,

Not when you start up a cold soaked RV in the -30 region. Heaters are a fail in that situation. It takes HOURS to warm up a battery in those situations.

It does work if the RV is in use.