Safe Temp for LiFePO

[Deleted member 1888]

I want to know what is the max cold and hot that you can safely operate LiFePO batteries at? Im trying to see if I can put them in a shed without having to insulate the shed, as I live in GA the weather is not that extreme in ether direction.

BTW I now have my land,and RV and will me making the move soon.(I may have convinced my wife to let me make a 48v system as the RV is a 50a, fingers crossed on that)

 

[ianganderton]

Lifepo4 will be damaged by charging below freezing so its best to have a couple of degrees of temperature spare room before that. I'm not sure on hot temperatures, my understanding is they are safe but lifespan reduces significantly over time.

It's always a good idea to insulate anywhere storing Lifepo4, they are one of the most expensive bits of solar systems so its worth treating the investment nicely to get max value from it. I think the best general rule of thumb is that this battery chemistry likes the same conditions as humans and ideally they are kept in a space that is part of a living space to assist this

 

[Dzl]

I agree with Ian, the simple rule of thumb is try to keep the batteries in the temperature range that you would be comfortable in, maybe a bit cooler.

There aren't exactly like hard black and white limits inside of which no damage occurs and outside of which damage immediately occurs.
Even with low temperature charging it is a balance between (1) temperature (2) c-rate (3) wear/damage.

But generally speaking,
The industry has mostly settled on 0*C / 32*F as the simplified lower limit for charging. Upper limit (across the board charging, discharging, and storage).

Absolute low temp for discharging is somewhere around -20*C I believe (but at reduced C-rates).

I'm not as clear on the upper limit, I believe over 30 or 35 is where degradation starts becoming a bigger deal and over 45-50 is usually looked at as a hard limit by cell manufacturers. This is an area where I would still like to learn more.

Currently, my rough ideal temperature limits would be approximately 10-30*C (50 to 86*F), and my slightly more lax target limits are maybe 5-35*C (40-95*F)

 

[Deleted member 9967]

As for the effects of cold on discharging.
You can discharge to as low as minus forty. Just don't do it often is all.
At minus 20 C it will only have 57% of its capacity. However, if you let the battery warm up to 20 C. Then it will recover and give you full capacity once again.
At minus 10 you will get only 68% of capacity.
And at 0 C, 82 % capacity.
At 40 C you go down to 95 % of capacity. So avoid heat as heat can kill a battery. Where as cold slows it down but the battery can recover from it.

Upper limits are 45 degrees Celsius. Anything above that and you damage the battery.
A safe upper limit is 35 C.

Warm the batteries up before charging them when below zero however. Zero is safe to charge at but use fewer amps when doing so. At least 10% or less of the cell volume. For example a 100 Ah cell should not be charged at more than 10 amp when at Zero degrees Celsius.

Hopefully this is helpful.

 

[JoeHam]

And the batteries do warm a small but significant amount during discharge.

On my motorcycle I can turn the headlight on for about 60 seconds on a cold day to increase the starting power.

On my jetski I had no load to turn on so I had to click the starting solenoid a bunch of times to “warm up” the battery. I ended up burning out the solenoid in one summer so that was an expensive lesson ?

Neither was used below freezing and a larger LiFePO4 battery would have likely been a better solution.

 

[grizzzman]

I have an LFP jump starter. It came with a resister for cold weather jumping.

 

[JoeHam]

I have an LFP jump starter. It came with a resister for cold weather jumping.

Resistors are cheaper than Yamaha starters!

Wish I had thought of that ?

When this AGM dies I will go back to LiFePO4 with a cheap resistor and a waterproof momentary switch.