Optimal current limit for a given continuous discharge rating?

[brownj24]

Does drawing 25 amps vs 35 amps from the battery controller on a 72 volt, 40 amp continuous discharge-rated lithium battery prolong battery life? Is there any reason to stay below 25 amps on a 40 amp rated battery?

I ask because my Phaserunner controller came programmed with 25 amp limit from ebikes.ca. I also bought the battery from them: https://www.ebikes.ca/shop/electric-bicycle-parts/batteries/b7208li-dt.html

Battery has a 40A continuous discharge BMS.

I'm wondering if I can get more power by increasing the limit to 35, which would still be below the 40A limit from the battery itself.

Thanks!

 

[john61ct]

Yes lower C-rate prolongs lifespan, until you get down well below 1C

Just because your pack is "rated" for higher, does not mean it can do anywhere near that IRL, especially if it is worn, or you bought the battery based on price 99.99% of pack sellers lie like crazy.

The key is, how many seconds at a time do you hit your peaks?

Anything over 20C won't last more than a minute or two out of 10min run, even with a great pack in great condition.

 

[Matador]

Yes. My view on the topic is that therr is no exact threashold value of current rating under which no damage will occurr and over which damage wil start to occur.

In other words, of you have cell that are rated 30A, it's not true that no damage will occur if you only use them at 20A. It's just the damage will occur sufficiently slow to be within what the manufacturer of the cells claim... That the cell will last at least X or Y number of cycle.

I see it as a linear relation. The higher the amps you draw, the faster your cell will age. If you double current draw, heat generated will quadrupe (in watts), if you triple current draw, heat will be x 9. Keep the cells as cool as possible.

I have VTC4 cells and intend to build a 14s10p pack for my 30A BBSHD. Pack shoud do 300A, but i won't use it above 30A anyways. Btw, 30A is eggagerated for the VTC4. Yes you could fully discharge them a 30A, but they will reach near 100 celcius. I consider the to be able to handle 20A max.

 

[goatman]

thats 2p??????? of 40T, heres a lifecycle test i did on them

https://endless-sphere.com/forums/viewtopic.php?f=14&t=106550

ES member PWD just did a pack for 15?amp/cell

https://endless-sphere.com/forums/viewtopic.php?f=6&t=98286&start=50#p1558794

did you get the satiator?

 

[brownj24]

Thanks for each of your replies - very helpful!