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pianotuna

Regina, SK, Canada

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Posted: 09/27/21 07:30pm Link  |  Quote  |  Print  |  Notify Moderator

Grit dog,

Further in the thread I do suggest that Li banks can be excellent--and if you roll your own, not an impossible price.


Regards, Don
My ride is a 28 foot Class C, 256 watts solar, soon to have SiO2 batteries, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

Grit dog

Black Diamond, WA

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Posted: 09/27/21 11:01pm Link  |  Quote  |  Print  |  Notify Moderator

^No doubt. And if I wanted/needed a large (reserve) and/or lightweight battery bank, I believe build your own Li is currently the setup to beat….inmost conditions.
While it would be slightly more convenient I actually would never get my money’s worth out of expensive batteries in our current scenario of camping like twice a year.
My point to FWC was, liFePO4s in cold weather are like that hot chick at the bar. Fun in the sack, nice to show off, high energy, but high maintenance.
Temperate weather or enough time and effort to keep her happy, they are great.
SiO2 are pretty intriguing as well.
And by the time we camp enough for our batteries to matter, technology will be better than it is currently. In the meantime, anything will work because I have generator(s).


2016 Ram 2500, MotorOps.ca EFIlive tuned, 5” turbo back, 6" lift on 37s
2017 Heartland Torque T29

StirCrazy

Kamloops, BC, Canada

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Posted: 09/28/21 07:38am Link  |  Quote  |  Print  |  Notify Moderator

FWC wrote:

Grit dog wrote:


Or more accurately, even though "you" personally want your rig "camp-able" at -30 deg and colder, LiFe's still have issues below freezing and you can't just "turn on he furnace" as one person suggested, although they will still "work" to discharge, IE provide power down to well below freezing (Not -30, someone can look it up though ). It's charging when the batteries themselves are around or below freezing.

Bottom line, they are a great option for lightweight, and duty cycle for warm weather campers. Not worth fiddling with if one is winter camping.
Although it appears some folks (on rvnet here anyway) really enjoy engineering and maintaining "off grid" solutions. I wonder if the "maintenance free" aspect of LiFe's is lost on the added $ and effort to make them work though.


Why would you not be able to turn on the furnace at -30?

PS, I winter camp extensively with my LiFePO4 batteries and have used LiFePO4 batteries well below -30 (just not in my camper).


because there only rated for discharge to -20C. but if you had a way to warm the battery up first you would have no problem. but thats interesting how are you prewarming your bateries or are you?

Steve


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FWC

The Wilderness

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Posted: 09/28/21 07:56am Link  |  Quote  |  Print  |  Notify Moderator

There is no physical reason that LiFePO4 batteries can't be discharged below -20C. I don't pre-warm them in any way, just use them. They are generally rated for -20, because they only test to -20C because 99.9% of their customers don't care about performance below -20C. However, some manufacturers do test down to lower temperatures and while they loose capacity at low temperatures, it is not nearly as bad as many battery chemistries:
[image]

Grit dog

Black Diamond, WA

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Posted: 09/28/21 08:57am Link  |  Quote  |  Print  |  Notify Moderator

^ FWC, why do I feel like you’re being intentionally vague just for the sake of argument?
You use lifes at -30 while camping but not in your camper. So what other possible applications are there and what are you using them for. Snomachines? Jumpstart pack? Headlamps? Off grid cabin battery bank?
How do you warm them to charge them? At -30 I’ll go on a limb and say that the discharge isn’t going to warm them enough to charge, or even if it does, charging won’t maintain them at 60deg warmer than ambient unless you’re heating them externally somehow.
If I’m wrong, please explain, as I’m always interested in learning something new.
And OP, I’ll apologize for all of us for the thread jack…

FWC

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Posted: 09/28/21 02:48pm Link  |  Quote  |  Print  |  Notify Moderator

I am not trying to be vague, I am pointing out that there really isn't a lower temperature limit to discharging LiFePO4 batteries, only to charging them.

This all arose because one user always brings up his specific scenario that he stores his camper at -37C and therefore LiFePO4 wouldn't work - my point is LiFePO4 could work, assuming he heats his camper, as he can use the LiFePO4 to power the furnace that he presumably uses to heat his camper to a livable temperature. This example is so out of the ordinary that it is really not a concern for 99.999% of RVers.

In most cases, if you use water in your camper, then you can use LiFePO4. The water system is much more sensitive to freezing than the batteries are.

As for my non-camper use - in my professional work I use LiFePO4 (and Li-Ion) batteries to power instruments for polar and high altitude research. Ambient temperatures regularly go below -70C.

Grit dog

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Posted: 09/28/21 03:37pm Link  |  Quote  |  Print  |  Notify Moderator

^Ok, fair enough. So you are a researcher in Anarctica. (Because the Arctic never gets that cold and by never I mean at least since LiFePO4 batteries have been around)
And apparently you’re out with your instruments on the coldest days of the year or decade in Antarctica. They’re not going to work bud.
I’d like to hear how you operate in -94F temps and colder….I’m just a greenhorn I suppose because much below -50F, nothing runs. At -60 you virtually can’t keep heaters fired to to keep fuel heated enough to fire the heaters to have a place to warm your batteries.
Even in the Arctic you don’t really go outside much below -50F.

Not everyone here has worked or lived above the Arctic circle so your claims may sound impressive but until you can explain the process I’m not buying it.
Oh, you must be a freelancer, because I don’t know of any agency or r company that operates in the Arctic that doesn’t have strict cold weather protocols that shut down virtually everything between -35 and -50F for safety.
But maybe that’s changed since I worked on the Slope in the winter.

StirCrazy

Kamloops, BC, Canada

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Posted: 09/29/21 07:43am Link  |  Quote  |  Print  |  Notify Moderator

FWC wrote:

There is no physical reason that LiFePO4 batteries can't be discharged below -20C. I don't pre-warm them in any way, just use them. They are generally rated for -20, because they only test to -20C because 99.9% of their customers don't care about performance below -20C. However, some manufacturers do test down to lower temperatures and while they loose capacity at low temperatures, it is not nearly as bad as many battery chemistries:
[image]


interesting, at -30 they have more capacity available than SIO2 (80% Vs 60%) first time I have seen a chart that shows preformance below -20.
is there a corasponding chart that shows if there is a impact on cycle life when used at these temps or if the amprage (flow) is impared?

Nevermind, I just saw that was at a 9 amp discharge. more than enough to run a furnace.......

Steve

FWC

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Posted: 09/29/21 08:16am Link  |  Quote  |  Print  |  Notify Moderator

You are assuming an awful lot here. Notice I said polar and high altitude, the coldest place we deploy instruments is not the poles, it is the stratosphere. For those measurements, we charge the batteries in the lab, on the ground, same way you would in your camper, then use them at ambient temperatures down to a low of around -80C (-112F) but typically more like -70C. Of course we insulate everything, but internal temps still get down around -40C.

But thanks for calling me bud and telling me that the equipment I use doesn't work.

Back to the actual point here - there is no reason you cannot discharge a LiFePO4 battery below -20C.

Grit dog wrote:

^Ok, fair enough. So you are a researcher in Anarctica. (Because the Arctic never gets that cold and by never I mean at least since LiFePO4 batteries have been around)
And apparently you’re out with your instruments on the coldest days of the year or decade in Antarctica. They’re not going to work bud.
I’d like to hear how you operate in -94F temps and colder….I’m just a greenhorn I suppose because much below -50F, nothing runs. At -60 you virtually can’t keep heaters fired to to keep fuel heated enough to fire the heaters to have a place to warm your batteries.
Even in the Arctic you don’t really go outside much below -50F.

Not everyone here has worked or lived above the Arctic circle so your claims may sound impressive but until you can explain the process I’m not buying it.
Oh, you must be a freelancer, because I don’t know of any agency or r company that operates in the Arctic that doesn’t have strict cold weather protocols that shut down virtually everything between -35 and -50F for safety.
But maybe that’s changed since I worked on the Slope in the winter.


FWC

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Posted: 09/29/21 08:26am Link  |  Quote  |  Print  |  Notify Moderator

StirCrazy wrote:



interesting, at -30 they have more capacity available than SIO2 (80% Vs 60%) first time I have seen a chart that shows preformance below -20.
is there a corasponding chart that shows if there is a impact on cycle life when used at these temps or if the amprage (flow) is impared?

Nevermind, I just saw that was at a 9 amp discharge. more than enough to run a furnace.......

Steve


Those discharge curves are for a SAFT 44Ah cell, so a 0.2C discharge rate.

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