cowpen
Member
- Joined
- Sep 6, 2018
- Messages
- 47
I've got over 2000 tested usable cells and am getting ready to start building my 14s??p packs. All were capacity tested on Opus chargers at 1A. Before committing to a build method I decided to make a small 12V (4s20p) pack just to get a handle on spot welding, fuses, connectors, and getting a battery with balanced capacity banks. So I pulled 20 cellls from the top end of my cull pile for the project. These tested initially in the Opus at between 1939 and 2141 for an average of 2131 mAh or about 40 Ah for the 4s20p pack.
So I pasted the capacities in repackr and got my pack distribution. Just for kicks, I decided to run each of the cells through the Opius again, but this time at the default 500 mA charge rate. The difference in capacities was surprising and unexpected. Most (3/4) of the cells tested significantly lower on the second test. The average difference was 68 mAh and the largest drop was over 500 mAh. High rated Samsung and LG cells that had tested poorly on the first test tended to do better on the second. Cells testing close to rated capacities usually tested worse.
So after that second test, it looks like I'll end up with some pretty unbalanced packs:
Not real happy with the consistency from these Opus chargers. What do you all think? Should I re-run the repackr with the new lower capacities, or stick with the distribution from the first run? I'm hoping all the effort to catalog keeper cells for my big packs wasn't wasted but after this I'm not so sure.
So I pasted the capacities in repackr and got my pack distribution. Just for kicks, I decided to run each of the cells through the Opius again, but this time at the default 500 mA charge rate. The difference in capacities was surprising and unexpected. Most (3/4) of the cells tested significantly lower on the second test. The average difference was 68 mAh and the largest drop was over 500 mAh. High rated Samsung and LG cells that had tested poorly on the first test tended to do better on the second. Cells testing close to rated capacities usually tested worse.
So after that second test, it looks like I'll end up with some pretty unbalanced packs:
Not real happy with the consistency from these Opus chargers. What do you all think? Should I re-run the repackr with the new lower capacities, or stick with the distribution from the first run? I'm hoping all the effort to catalog keeper cells for my big packs wasn't wasted but after this I'm not so sure.