Strange behavior

[LilHeidi]

I have a number of cells at my place, currently testing them, but the behavior of some of them puzzles me.
Precisely, a cell connected to the ZKE shows immediately 3.45V upon charging...it charges to full capacity but takes almost two days...and discharges at full capacity at the normal time.
The same happens if I raise the voltage, or lower it...the voltage gets to the selected level in seconds...then the current trails slowly until it reaches full capacity...is there anyone with some logical explanation for this behavior? The temperature of the cell doesn't rise nor there's any swelling or anything...does this means it is dead?
Puzzled...

 

[time2roll]

Does the capacity match the specification?

 

[LilHeidi]

As seen from the above, yes. Completely.
The capacity is there either by charging or discharging...however, due to early reach of nominal voltage current gets hammered and the whole cycle of charging takes really long time.
This is what really confusing me...capacity is there, no bulging no heating yet the whole story seems very weird.
Therefore I asked for anyone with some experience in this field...perhaps controller inside the cell itself...maybe...donno...