IR Question

[3dwantabe]

I know that the lower that the IR or ohms is better to have in your packs. But I'm not sure what the numbers mean and what's an acceptable limit and IR difference between cells in the same pack. What's the high limit that would tell you the pack is on it's last legs. I am running a meanwell 24v 40amp ps on a powerlab 6. I just purchases 6 revlectrix 3s 2200 diamond label packs and here are the number on the first charge. What do they mean? What do the numbers tell me to watch out for?


Pack Cell 1 Cell 2 Cell 3
1- 4.5/ 4.4 /3.9
2- 4.8/ 4.5 /4.4
3- 4.6/ 4.5/ 4.6
4 -3.7/ 3.6 /3.4
5 -4.1/ 4.1/ 4.1
6- 4.8/ 5.0/ 4.6

Each pack was charged separately @ 2.20A

[3dwantabe]

Sorry for the bunched up numbers, when I tried to fix it they posted the same bunched up way.

[Gregor99]

IR can be used as an indicator of pack health. IR is relative to pack size and C rating. The large the pack size (in mah) the smaller the IR. The higher the C rating on the pack, the lower IR (should be). For comparison, IR measurement should be done at 70f-71f resting for an hour. IR values on the Powerlabs stabilize midway through the charge.

More background and tools:

This is the “Simple LiPo Performance Tool” Discussion thread.
http://www.rcgroups.com/forums/showthread.php?t=1577989

The Lipoly Objective Performance Database
http://www.rcgroups.com/forums/showthread.php?t=1578001

Actual C rating and FOM calculation tool
http://www.jj604.com/LiPoTool/