Does battery C rating drop with capacity?

[Fordulike]

Most peeps know that our batteries don't last forever, with the total capacity dropping with age and use.

Can any tell me if the C rating drops also, as the total pack capacity becomes less over the years.

Example:

Two identical 48v 12Ah 2C rated packs

Pack 1:

Brand new, still 12Ah in pack. I would expect it to be fine with a 24 amp discharge rate.

Pack2:

3years old, 8Ah left. Would it still be fine with a 24 amp current draw, or would you have to adjust controller settings accordingly?

 

[Deleted member 4366]

As the cells age, the internal resistance increases, so you get more voltage sag.

 

[D8ve]

If the C rating remains the same then the three year old 8ah battery would be 16ah max.

 

[Fordulike]

Thanks for the replies guys. So in your opinions, would you just keep drawing the same amps from the pack, regardless of age, until it pretty much dies.

Or would you lower the controller's max current draw, say every year, to compensate?

 

[Deleted member 4366]

leave it at 24A. It sounds like it's pretty well knackered anyway.

 

[Fordulike]

leave it at 24A. It sounds like it's pretty well knackered anyway.

Yeah, I think you are spot on with the voltage sag issue of older cells. The voltage just seems to take longer to recover after a bout of heavy current draw.

They were only examples above, but the actual pack is one and a half years old with around 200 cycles.

A Samsung 30Q pack is in the pipeline fairly soon, so they should fare better than the 29E's.