Is the problem my batteries or my new battery charger? (Battery analyzer charge test mode)

[ossipago]

Delurking because I am having trouble understanding the behavior of my new Opus BT-C2400.

The Opus has a charge-test mode where it charges, discharges, and then recharges a battery and reports its capacity.

My confusion is that the charge-test mode reports numbers that don't make any sense for some of AA batteries - e.g. 400 mAH, etc. This despite the fact that they might go through the last charge cycle for 4 hours at 400 mAH.

Most of my cells are old (as old as 10 years in some cases), and I understand that means that may have run down their capacity. But could a cell with, say, 50% capacity break the charge-test mode in some way? If so, why? Or is the more likely culprit a faulty charger?

I've had smart charger/analyzers before and don't remember ever having an issue like this.

 

[uk_caver]

Does it give consistent results for a given cell?
Do all slots behave the same way?

It would not be too surprising if AAs which had degraded to the point of having an actual capacity of 400mAh also had relatively high resistance.
Looking at the manual:

Note: When attempting to charge cells with high
impedance, the charger will not reject the cells as with
some other chargers. Instead the cell will be charged at
a reduced current from the programmed setting. This
will allow charging of high resistance cells so that they may
be cycled to improve their capacity and internal resistance.

It might be the case that a ~400mAh capacity with high resistance could *appear* to charge for 4 hours at a selected 400mA, but was actually charging at a lower rate.

Were the cells actually charging at 400mA for 4 hours?
That is, (assuming the charger displays the relevant data during a CHARGE-TEST cycle), does the display consistently show instantaneous charge current of ~400mA during charging, and/or does the accumulated capacity display show data consistent with a 400mA charge current?

 

[ossipago]

I ran the same batteries through the same test cycle again, and the cell in question didn't have a 400 mAH capacity, it discharged and recharged at 1700 mAH. Maybe the charger has some wonky behavior specifically when dealing with cells that have run down past a certain point. I'm not sure why that would be the case. Still wondering if I should ask for an exchange.

 

[Lynx_Arc]

Nimh cells can often "recover" capacity that they lost while not being used for years by running them through several charge/discharge cycles. I have a Lacross BC900 that has a refresh mode that will charge/discharge continually till it detects no more improvement in capacity. I've brought back batteries around 500mah capacity to 1700 mah before but often these recovered batteries are still prone to further deterioration.