this is why

[pianotuna]

Hi Folks,

This is why Li batteries are not a good fit for me.

https://weather.gc.ca/city/pages/sk-32_metric_e.html

-40 on Wednesday night.

[pianotuna]

Little Bill,

My RV is highly modified to withstand cold. Look at the full time forum where I have posted the upgrades I've made. On my maiden trip, the pex water hoses froze, and it was not particularly cold.

I agree rv use in extreme cold is somewhat rare, however I know of two other RV'ers who have managed to boondock at -40 (and not just one night), so it may not be as unusual after all. I've missed my chance to join the -40 club this year.

[FWC]

I am still not following - why would it taking 3 hours to heat the living quarters mean that Li would not meet you needs?

Regardless of the battery chemistry, if you are going to use them in very cold temperatures, it almost always makes sense to heat the batteries. The capacity of all batteries is greatly decreased at low temperature. With FLA at -40F/C you can get about 20% of their rated capacity, with AGM/Gell/SiO2 you can get about 40%. LiFePO4 is a bit better and retains about 50% of its capacity at -40. The other big issue is battery voltage decreases with decreasing temperature and internal resistance increases, so if you are using you batteries to power something like an inverter with a high current draw and a low voltage cut off, you will only be able to use a small amount of the already reduced capacity at low temperatures.

Ideally you would use the heat from the living space or a furnace vent to heat the batteries, but even if you had to use half the batteries own power for heat you would still be better off than using the batteries cold.

[LittleBill]

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.

[pianotuna]

As I said earlier, I've boondocked at -37 C (-34 f). If I were not in the Toronto area looking after a sick friend I would have gone on a pavement trip just to test things out at -40.

I know the Yamaha Generator (electric start) will fire up at -26 C(it was not happy but caught on the 4th try--with a three minute wait between attempts). I do have a magnetic block heater for it, which has never been used. I have not needed to heat the propane tank, but again I could do so with the magnetic heater.

I know that at -26 C (-15 f) it takes over 3 hours with all the energy from the generator and the furnace running constantly to warm up the "house" to temperatures where one doesn't need a winter coat inside the RV (about 10 C {50f}). The heat output is about 28,000 BTU's combined. That's why even an installation of LI inside the living quarters would NOT meet my needs, even if the batteries were equipped with warmers.

My own personal belief is that no battery bank should be in the living quarters, unless there is a sealed box vented to outdoors, but others may do as they wish. After all, it is a free country.

The battery bank, starter battery, and (now) generator battery are all maintained by a solar system.

[StirCrazy]

pianotuna wrote:

I have room for 7 group 29 batteries. If it will fit, I'll replace the starter battery with an SiO2 as well. That ought to leave me close to 7 kwh of usable storage.

Maybe when it is 30 above, but at -40 that will work out to about 3kwh using SIO2. still much better than 0.5kwh agm would give you at thoes temps.

[StirCrazy]

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

[StirCrazy]

time2roll wrote:
I don't think I could survive at that temperature unless I had continuous utility power to heat both the battery and propane cylinders. In which case LFP would be fine.

If power went out, I think I could still make the night to roll out in the morning.

I can't imagine SiO2 retains all its rated energy at that level either.

When do we get a trip report? 😉

it doesnt, at -20C it only has 80% of its original capacity, 60% at -30C, and at -40C/F it only has 40%.

https://azimuthsolar.ca/wp-content/uploads/2019/01/Lead-Crystal-Chart.png

Steve

[2oldman]

FWC wrote:
Firstly it doesn't seem like the OP is planning on going camping at -40C.

I believe he lives in that right now.

[FWC]

valhalla360 wrote:

pianotuna wrote:
valhalla360,

Exactly so. I'll be glad when I can get to B.C. to buy 7 or 8 SiO2 batteries.

I'm still not seeing the point of your original post.
- If you need a big battery bank for other purposes but will have access to shore power during extreme cold, there are simple solutions to make lithium work.
- If you don't need a big battery bank and will always have shore power, just get the standard single battery and save yourself a lot of money.

Maybe it would be better if you lay out your use case.

Agreed. This has been described for years, but doesn't make sense to me either. Firstly it doesn't seem like the OP is planning on going camping at -40C. But if he is, it would be very interesting to see what sort of camper could survive this. A mass market RV certainly wouldn't be useable for a whole variety of reasons, lack of insulation, insufficient heat, moisture management, tanks etc.

Secondly, I assume if he is planing on using the camper, he has some sort of auxiliary power and heat, shore power, a generator and a furnace with which to warm his camper. If you are actually going to inhabit the camper, humans, water and food are more temperature sensitive than any sort of batteries.

[pianotuna]

valhalla360,

My use is rural business trips of two weeks, often in cold weather. I may have a single 15 amp circuit, but not always.

Since I'm in a class C, the propane tank is fixed. There is no access to refill in small towns. Therefore I wish to run off 120 power for all energy needs including space heating.

I will not sleep with a generator running. Hence the need for a large capacity battery bank.

I have room for 7 group 29 batteries. If it will fit, I'll replace the starter battery with an SiO2 as well. That ought to leave me close to 7 kwh of usable storage.

[RetiredRealtorR]

Bionic Man wrote:
Sounds like a good reason to move south. I have no desire to live anywhere where those temps are common.

x2 . . I have no idea why anyone would endure that kind of cold.

[jaycocreek]

Having lived and worked in similar temps as pianotuna,I wouldn't own lithium either..To many things to go wrong that could permanently damage the lifepo4 batteries...I don't miss those days..


Jayco

[valhalla360]

pianotuna wrote:
valhalla360,

Exactly so. I'll be glad when I can get to B.C. to buy 7 or 8 SiO2 batteries.

I'm still not seeing the point of your original post.
- If you need a big battery bank for other purposes but will have access to shore power during extreme cold, there are simple solutions to make lithium work.
- If you don't need a big battery bank and will always have shore power, just get the standard single battery and save yourself a lot of money.

Maybe it would be better if you lay out your use case.

[pianotuna]

valhalla360,

Exactly so. I'll be glad when I can get to B.C. to buy 7 or 8 SiO2 batteries.

[valhalla360]

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.