Mikethezipper
Member
- Joined
- Jul 7, 2018
- Messages
- 121
Howdy,
A while back I purchased around 2,500 of the Panasonic NCR18650Bcells from a local company that had been making battery packs for drones but lost their govt contract. The cells are assembled into packs and although they were cycled - I was told they had barely used any of them.
So far I've taken apart about 500 cells worth of these (the packs are put together pretty darn well) and tested them, which has taken a ridiculous amount of time. Every single cell is at 3.2v or above. When I capacity test them, every cell is showing 3400-3600mah per cell, so they are testing at their rated capacity of 3400mah.Considering that I can only test ~24 of these a day, it's taking a long time. After that I have to check them for self-discharge so it's adding another month on top of that for each cell.
As I test these when I'm at work, I can't do a good job of checking for heaters. What I'm wondering is whether it's worth checking for SD cells, and if I should be worried about heaters. Is this a property that arises in heavily used and abused cells, or is this pretty much random and I should go ahead and do the full testing on all my cells?
I'm not sure if it was Wolf - but another thread on here showed a strong relationship between IR of a cell (assuming we're testing all the same cell here) and the likely-hood that it won't be worth the effort to capacity test etc as cells with unusually high IR for that type of cell also tend to either have low capacity, be heaters (duh), or be self-discharging cells.
What do ya'll think? The safest answer would be to just go ahead and check for SD on these cells, which adds quite a bit of time. But is it reasonable? If they were SD cells, shouldn't they have really low voltages by now? They have sat for about a year before I got to them, so I think them being at a voltage above 3 is a sign they are not SD cells. However, they are in 8s8p packs, so maybe an SD cell would be held up by other healthy cells. Is that reasonable?
A while back I purchased around 2,500 of the Panasonic NCR18650Bcells from a local company that had been making battery packs for drones but lost their govt contract. The cells are assembled into packs and although they were cycled - I was told they had barely used any of them.
So far I've taken apart about 500 cells worth of these (the packs are put together pretty darn well) and tested them, which has taken a ridiculous amount of time. Every single cell is at 3.2v or above. When I capacity test them, every cell is showing 3400-3600mah per cell, so they are testing at their rated capacity of 3400mah.Considering that I can only test ~24 of these a day, it's taking a long time. After that I have to check them for self-discharge so it's adding another month on top of that for each cell.
As I test these when I'm at work, I can't do a good job of checking for heaters. What I'm wondering is whether it's worth checking for SD cells, and if I should be worried about heaters. Is this a property that arises in heavily used and abused cells, or is this pretty much random and I should go ahead and do the full testing on all my cells?
I'm not sure if it was Wolf - but another thread on here showed a strong relationship between IR of a cell (assuming we're testing all the same cell here) and the likely-hood that it won't be worth the effort to capacity test etc as cells with unusually high IR for that type of cell also tend to either have low capacity, be heaters (duh), or be self-discharging cells.
What do ya'll think? The safest answer would be to just go ahead and check for SD on these cells, which adds quite a bit of time. But is it reasonable? If they were SD cells, shouldn't they have really low voltages by now? They have sat for about a year before I got to them, so I think them being at a voltage above 3 is a sign they are not SD cells. However, they are in 8s8p packs, so maybe an SD cell would be held up by other healthy cells. Is that reasonable?