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Open Roads Forum  >  Tech Issues

 > Lifepo4 cold temp cut off 23F or 32F?

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theoldwizard1

SE MI

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Posted: 11/22/21 01:29pm Link  |  Quote  |  Print  |  Notify Moderator

The issue is charging more than discharging. Also, whether you were in use before the temperature dropped below freezing.

If you are continuously discharging, you CAN go from above freezing to slightly below freezing (23F sounds reasonable), but do not try to recharge at the temperature.

pianotuna

Regina, SK, Canada

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Posted: 11/22/21 01:40pm Link  |  Quote  |  Print  |  Notify Moderator

2oldman wrote:

23.. 32? Looks like dyslexia.


Very Clever!


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.

time2roll

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Posted: 11/22/21 01:49pm Link  |  Quote  |  Print  |  Notify Moderator

theoldwizard1 wrote:

The issue is charging more than discharging. Also, whether you were in use before the temperature dropped below freezing.

If you are continuously discharging, you CAN go from above freezing to slightly below freezing (23F sounds reasonable), but do not try to recharge at the temperature.
A good BMS will block the charging at low temperature and block discharge at an even lower temperature.


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jaycocreek

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Posted: 11/22/21 02:21pm Link  |  Quote  |  Print  |  Notify Moderator

[image]

noteven

Turtle Island

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Posted: 11/22/21 03:15pm Link  |  Quote  |  Print  |  Notify Moderator

pianotuna wrote:

noteven wrote:

Some battery makers are now building self heating LiFeO4 batteries.

No they don’t use their own amp hours to heat. The batteries can deliver energy down to -20C battery temp.

They use energy from the charging source to warm the cells. Then they begin to charge.

Lithium batteries can accept charge at very high rates.

This is why a small generator or engine alternator charging is probably step one in a lithium system then do the solar spend to round out the system, especially if you camp in winter, forest, shade, or rainy lands.


I wonder how long the heater would take to warm the battery bank at -37 c?

Best possible charge rate for best cycle life is 0.2 c. A 0.5c works well, too. Yes, you can charge faster--but with a trade off in cycle life.

Battleborn batteries have a heated version--and it DOES draw from the battery to keep warm unless there is external power available.


If I were using them in a unit capable of -37C I would have them installed inside the heated envelope. If I had to let the unit freeze to ambient in storage at 25lbs each I would pick up the batteries and put them somewhere warm, partially charged, not needing any fussing with in storage, until I needed them again.

If you are where it gets cold, don’t buy self heaters that use their own energy would be a n option.

A guy could also use SiO2 batteries if actual cold exposure is common in the “mission”.

noteven

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Posted: 11/22/21 03:18pm Link  |  Quote  |  Print  |  Notify Moderator

Ray at Love Your RV channel did a cold lithium charging test using a freezer and actual measurements.

Spoiler The battery does not blow up and fail at 31.9F

jaycocreek

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Posted: 11/22/21 03:38pm Link  |  Quote  |  Print  |  Notify Moderator

noteven wrote:

Ray at Love Your RV channel did a cold lithium charging test using a freezer and actual measurements.

Spoiler The battery does not blow up and fail at 31.9F


I have also read that charging at a lower voltage is okay when it's that cold..Good test for Will instead of all the guessing floating around the net..The last video I saw of Wills,he was talking about charging a lfp with frozen cells which...At what temp does a Lifepo4 cell freeze?

dedmiston

The West

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Posted: 11/22/21 04:19pm Link  |  Quote  |  Print  |  Notify Moderator

Lwiddis wrote:

I've seen some manufacturers say it is ok down to 24 but no experts. They say 32.


Pretty ironic from the guy who says so often to ignore the experts and do whatever the manufacturer says.

(DISCLAIMER: I don't know anything about these batteries, but I'm a self-proclaimed expert in irony. And yes, I appreciate the irony of a moderator calling Lwiddis out.)


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wa8yxm

Davison Michigan (East of Flint)

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Posted: 11/22/21 05:06pm Link  |  Quote  |  Print  |  Notify Moderator

pianotuna wrote:

It depends in the individual maker.


I will second that. Slight differences in both the make up of the battery and the paranoia of the maker (IN this case paranoia means their desire to be cautious) A more cautious maker will name a higher cut off temp.


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StirCrazy

Kamloops, BC, Canada

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Posted: 11/22/21 05:31pm Link  |  Quote  |  Print  |  Notify Moderator

23F is -5C, which is the lowest cold weather charging temp listed by the Prismatic cell manufactures, so thats not the brands limit thats the actual cell manufctures limit. most rebranders/assemblers would put that to 32F to give them self a bit more protection from warenty claims.

Steve


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