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Cell capacity at different temperatures
#11
Its nothing new that temperature affects capacity.. it also affects the testers used...

This goes back to My first videos where i stated clearly that the envieonment you do the tests in need to be consistent.


And IF you have Read any datasheet or papper about batteries this should not come as a suprise but Still People tend to be supprised? Smile

As an example a cAr starts easier the 2nd crank du to the battery heated Up..or when we fly quads or race cars we preheat thebatteries to gain run time and capacity.


IF you look for a Variable to calculate capacity derived by temperature you can find Them in datasheet and scientific papers Smile

I understand people like to figure stuff out Them self but this is a thread that isnt anything new Smile
thunderheart likes this post
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#12
While it is nothing new that temperature affects capacity, do you know if cycle life can improve in cooler, but not too cold, conditions, similar to how limiting depth of charge/discharge increases cycle life? Every data sheet I have ever seen only shows cycle life at 20 or 25*C. And we all know that 40*C will kill cells twice as fast or faster. But how about like 10 or 15*C? I had an idea of using a chest refrigerator with an external regulator set for like 15*C as the ultimate fire-resistant, low humidity, temperature regulated battery cabinet, assuming it could support the weight of the batteries, of course.

Also, for capacity testing, you need A LOT of cycles to see any results, unless you start with cells that are pretty worn out to begin with. In my test, I was expecting results right away because everyone says generic cells are bad without any sort of proof. Are you going to start a thread on your cycle testing? I'm curious about the cells you are using - age, % of capacity, brand, etc.
Formerly known as Dallski
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#13
Not sure IF use during 10c yield longer life... But doing the math you get more cycles but less total capacity. So without data i would say No total gain in the end.

Thats One of the things i havent seen either nor tested since it takes years to test
Ibiza likes this post
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#14
I have not read many data sheets.
Having said that the only ones which have mentioned a temperature was just a single temperature - nothing about "W capacity at X temperature" and "Y capacity at Z temperature"
While everyone here probably knows that temperature can affect chemical reactions, this is a theoretical idea until it has a practical application.
Is the effect something big or small, will it affect what people are trying to achieve, or not?
I think what I have observed and posted about might change how people want to do thier testing to create balanced packs.
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#15
I cycle my power tool batteries sometimes three times a day.
Hilti 22v5.2Ah a pack.
Drill, jigsaw, circle saw, grinder and such, most important one, the radio
I use them in minus 15c and plus 40c. Charge them in the full sun, rain, ect
Two packs are running for two years know.
Maybe its how the bms is programmed for the soc, but i don't have the feeling that they are losing capacity.

For my powerwall i am not really afraid of sub zero temperatures, but i have to dig in to it more.
So get a second opinion on this.

As far for my testing endeavors, especially discharge, there is a huge difference with temperature.
15c 20 and 25c.
Winter is coming, it would be fun to see how known cells are going to react at 10c 5c 0 -5 and -10c

Best
Still learning English. Learning Li ion and solar technology.

4200 cells in packs Exclamation above 2500mah and 90%soh.
1500 waiting for testing.

Saving for 3 times phoenix inverter 48/3000 230v to gain also 380v
3 chargers?

Time is our enemy, must work to, the sun is our friend, must relax to.
With best regards
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#16
There is a huge difference in - for Lithium Ion. You can loose easy 50% of the available capacity. (Loose as in useable)
The capacity as such is not "Lost" since as soon as they get warm again you can use it again.

Its like that for most of the chemistries. The reason EV cars have cooling/heating around their packs as example or why a car is hard to start during winter.
The Ultimate DIY Solar and build place
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Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 83kWh LiFePo4 | 10kWh 14s 18650 |  66*260W Poly
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#17
So basically Hilty packs are "limited" to 50% soc, sort a speak.
That's why i don't notice the difference between summer and winter.
And when in use, they will warm up a little.

But for the powerwall you want to have more out of it, so you will notice.
And must apply some heat to them.
I assume in Sweden it would be more difficult to ride a EV?
The average temperature is a bit lower.

Would LTO not be more efficient in a car, or it does not matter?
Still learning English. Learning Li ion and solar technology.

4200 cells in packs Exclamation above 2500mah and 90%soh.
1500 waiting for testing.

Saving for 3 times phoenix inverter 48/3000 230v to gain also 380v
3 chargers?

Time is our enemy, must work to, the sun is our friend, must relax to.
With best regards
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#18
@ajw22 in the case of Li-Ion that is not valid. Li-ion works great in low temperatures and it's a disaster at high temperatures.
This is valid for anything from smartphone batteries to 18650 cells.
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#19
Powertool batteries tend to heat up yes. You can notice it in beginning or on cheap ass gear but most powertool brands will work due to high current creating inside the cells Tongue
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Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 83kWh LiFePo4 | 10kWh 14s 18650 |  66*260W Poly
Upcoming: 14S 18650~30kWh | Automatic trip breakers, and alot more
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#20
Can you identify the cell manufacturer and part number? 
If so, please share that information since it seems you're committed to life-cycle testing these cells.
Also, could you include the charge time, the rest time, and the discharge time - in otherwords, what your cycle looks like?
And how often you cycle - how many times a day?
As to your question on how temperature affects cells, the "aging path" is affected by cell temperature, cell nominal or average state-of-charge, and cycling severity.
Even daily thermal cycling of the cell - similar to the "cold start" of an automobile on the driveway needing time to "warm up", affect cell aging.
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