Charging at less than 1/3C

transposon

100 W
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Nov 24, 2011
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Massachusetts
I have read that there is a benefit to slower charging in regards to cell cycle life. Does this benefit scale linearly down to 0C, or is there a point where slower isn't better. I am guessing this has to do with internal temperature of the cell. As a general rule, is going below 1/3 C helpful or are you just wasting time at that point?
 
0.4C is the lowest you need to go at 77°F / 25°C for longevity.

When the cell is hot you can go higher.

Close to freezing, then you must go much slower.

And other factors like discharge C-rate, and avg DoD% have a much higher impact

if those are abusive then the charge rate won't have much effect.
 
Thanks for the info. 0.4C is pretty fast charging. I'm glad to hear that cells don't need to be babied that much during charging.
 
Most people in a hurry consider 1C to be slow, and in a very high C-rate discharge use case

or low avg DoD cut off

may not see any longevity benefit by going slower.
 
This is very useful info to randomly read and be spoon fed. So far I've only really bothered to think about controllers, but batteries are now my biggest problem.

john61ct said:
0.4C is the lowest you need to go at 77°F / 25°C for longevity.

When the cell is hot you can go higher.

Close to freezing, then you must go much slower.

And other factors like discharge C-rate, and avg DoD% have a much higher impact

if those are abusive then the charge rate won't have much effect.

Could you elaborate on the max discharge rate and at what point that becomes unimportant/will start to reduce life?

In my case i have 2 batteries... 13s3p Samsung 30q and 20s4p molicell P42a. They're rated at allegedly 15A/30q and 30A/P42a so allegedly I've got about 45 and 120A allowable discharge, which gives me enough kW for a lot of fun.

But what's the realistic value to keep them happy for longer?

What about short pulses at say twice that compared to continuous 1x compared to...

Thanks again!
 
transposon said:
As a general rule, is going below 1/3 C helpful or are you just wasting time at that point?
As a "general rule" going below 0.3C isn't necessary, but there are exceptions to every general rule. Like when attempting to revive a Li-ion cell/p-group/battery.
john61ct said:
Most people in a hurry consider 1C to be slow, and in a very high C-rate discharge use case
The highest burst discharge rating of a high performance lithium polymer battery is 45C-50C. The highest charge rate of a high performance LiPo battery is 15C.
john61ct said:
Everything I've stated pertains to lithium chemistries only
Just Li-ion or also LiPo as some ES battery threads are about lithium polymer cells ...
https://endless-sphere.com/forums/viewtopic.php?f=14&t=112690
https://endless-sphere.com/forums/viewtopic.php?f=14&t=112458
https://endless-sphere.com/forums/viewtopic.php?f=14&t=97763
https://endless-sphere.com/forums/viewtopic.php?f=14&t=111704
https://endless-sphere.com/forums/viewtopic.php?f=14&t=44100
https://endless-sphere.com/forums/viewtopic.php?f=14&t=93598
https://endless-sphere.com/forums/viewtopic.php?f=14&t=109341
 
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