I have almost 200 Winston Thundersky cells of 60Ah , about 9 years old. I think there is still for 80% capacity in them, so at least 30kWh to be used.
However, some cells are probably not that healthy and will die quickly.
They were never paralleled.
What are acceptable internal resistance values for old Winston Thundersky cells?
They had less than 0.55mOhm when new.
I have an YR1035+ internal resistance tester. Some cells are now at double that, for example 1.2 mOhm.
I'm going to measure them all, and filter out ones with very high values (like 2mOhm and above)
But they will get an easy life with low C rating (far lower than 1C)
However, I want to parallel up to 12 of them (16s12p) and I don't want the bad ones bringing down the rest.
Would it be a good strategy to test them all for internal resistance, and filter out the bad ones (that have way more than double the original internal resistance).
Then, with the remaining good cells, just mix them (low with high resistance paralleled)
You would think it would make sense to group them by internal resistance, but then you would just create parallel blocks of weak ones, and parallel blocks of good ones, putting that in series will probably cause big imbalance in the pack.
I guess it would be good to capacity test each cell. But that will require lots of work and time.
Alternatively, I could just hook them all up parallel with a fuse on each cells.
That would be cost increasing, but I need some extra busbars anyway for connecting them parallel, might as well be fuses.
And of course I will put a strong active balancer on it, for example 10 Amps.
However, some cells are probably not that healthy and will die quickly.
They were never paralleled.
What are acceptable internal resistance values for old Winston Thundersky cells?
They had less than 0.55mOhm when new.
I have an YR1035+ internal resistance tester. Some cells are now at double that, for example 1.2 mOhm.
I'm going to measure them all, and filter out ones with very high values (like 2mOhm and above)
But they will get an easy life with low C rating (far lower than 1C)
However, I want to parallel up to 12 of them (16s12p) and I don't want the bad ones bringing down the rest.
Would it be a good strategy to test them all for internal resistance, and filter out the bad ones (that have way more than double the original internal resistance).
Then, with the remaining good cells, just mix them (low with high resistance paralleled)
You would think it would make sense to group them by internal resistance, but then you would just create parallel blocks of weak ones, and parallel blocks of good ones, putting that in series will probably cause big imbalance in the pack.
I guess it would be good to capacity test each cell. But that will require lots of work and time.
Alternatively, I could just hook them all up parallel with a fuse on each cells.
That would be cost increasing, but I need some extra busbars anyway for connecting them parallel, might as well be fuses.
And of course I will put a strong active balancer on it, for example 10 Amps.
Last edited: