[MathisLaurant]

I have been thinking about this for a few days and trying to reason through it but I am not sure if I am correct in my thinking. I want to ensure that the individual battery cell does not exceed the manufacturers specifications.


If my thinking is correct...:


Lets say that we have an 80s6p pack
max cell volt of 4.2 v

nominal 5 amp-hr per cell
max 2C



That means that there are there would be 480 cell are in this pack
so if the pack is providing 80 amp of current to a load



would it simply be:

80A / 480cells = .1667 A/cell


At max 2C-rate

4800A/ 480 cells = 10A/cell


is that correct? it just seems so simple.

or do you have to consider it in a different way?

 

[jbman]

Multiply the C rate by the amp hours of the pack to get the discharge rate your battery can support. 5AH per cell with 6 cells in parallel gives you 30AH. A C rate of 2 means you can pull 60 amps from the pack without damaging it.

Sent from my SM-N960U using Tapatalk

 

[brian_]

5AH per cell with 6 cells in parallel gives you 30AH. A C rate of 2 means you can pull 60 amps from the pack without damaging it.

True... and if the difference between this and what you were originally thinking isn't apparent...

Lets say that we have an 80s6p pack
max cell volt of 4.2 v

nominal 5 amp-hr per cell
max 2C

That means that there are there would be 480 cell are in this pack
so if the pack is providing 80 amp of current to a load
...

This means the cells are in groups of six cells, connected in parallel (there's the 30 Ah capacity), with 80 of these groups connected in series. "In series" means that the same current groups though each group of cells, so the same 80 amps goes through each group... no multiplying the current by the total number of cells.

So, 80 amps divided between six parallel cells is 13.3 amps per cell. That's 13.3 / 5 = 2.7 times the cell capacity... or a discharge rate of 2.7C. That assumes that parallel cells evenly share current, and they don't quite, so it's only an approximation.

Working instead from the allowed discharge rate, at 2C you would be able to draw 10 amps per cell, or 60 amps per group of six parallel cells, so 60 amps for the full battery.