this is why

SiO2 are much better than regular AGM, which are better than flooded. They have little or none of the monkey business needed for Li chemistries.

There is only one Li chemistry (Lithium Titinate) that would meet my weather needs (not wishes), but it is $1800 per 100 amp-hours, and many would be required because the recommended discharge rate is rather low. SiO2 can do 4C continuously.

Li are not well suited to cold except for the aforementioned above.

I fail to see how I could warm li batteries up to where they could be charged without using shore power, or a generator. Physical space will only allow 7 group 29 jars. Li are not that much smaller in dimension, and for MAXIMUM cycle life really only have 50% usable (40% to 90%).

Li do not love to be float charged. That means adding complications to the solar charging system for storage. SiO2 don't mind float at all.

I believe LI are a excellent battery for the middle of USA. Farther south things get a little complicated as LI apparently dislike high temperatures.

LittleBill wrote:

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.

ahh I was talking about how you would do it using solar and with out having one of the warming BMSs as long as its above -20C as you can discharge just can't charge with most cells.

LittleBill wrote:
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.

the ops case is extream, but not uncomon. I have taken a camper across country in -35 and it isnt fun. first the camper wasnt made for cold weather at all and the batteries would barly last the night after driving all day. LFP would have been a good send as I could have pluged in an electric heater on an inverter also with enough battery. this isn't a failure of LFP batteries for the OP but rather a failure of his in trusting the instalation of a totaly sealed battery that doesnt off gas whats so ever in the heated space. they could very easialy heat up his rv, and in the space he is going to get 7kwh in the summer he could get three times the power which would let him run even more electric heaters and warm it up even faster.

the bigger question is, why do people have to bash products and go on missions to make people think they don't work, becasue they don't want to use them like there made to be used?

if you don''t want to put them inside thats not a short coming of the battery, its kinda what they were made for, but just come out and say yes they are great batteries and would work just fine if I put them inside the heated space but I don;t want batteries inside so I cant use them. simple, arguments are all done and your not falsely bashing products and trying to promote a different one which isn;t as good as better. yes SIO2 have there space but they still have most of the limitations of lead asid batteries except they have a stupid factor built in. so if your stupid and forget to plug in your tractor they will probably start, or if your stupid and forget to watch the charge and run them down theyll be fine for a few times........ other wise they still lose a lot of capacity by temp, have charging speed limitations, are big, and are heavy.

pianotuna wrote:

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.

As you say, it's a free country but since there is no off gassing, there really isn't a need to put them in exterior vented boxes.

https://www.rvia.org/news-insights/rv-industry-making-changes-address-growing-popularity-lithium-batteries

No one is going to force you to buy a lithium battery bank if you don't want one but you seem to be coming up with ever more creative justifications. If you don't want them, simply don't buy them. There are reasonable solutions.

My 12-volt wet cell batteries have served me well in very cold weather. I have no desire to camp in below freezing conditions. YEP

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.

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.

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.

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.

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.

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