The problem with multi chemistry smart battery chargers is that they will occasionally think that a nickel chemistry battery is unsafe to charge, assuming it is a lithium battery that is too low to charge safely. This is good if you actually have a lithium battery that is over discharged, but frustrating if you want to charge a nickel chemistry battery that is safe to charge.
To get the smart charger to charge the nickel battery anyway, I have to connect the battery to the 3.3 volt rail on my bench power supply for about 30 seconds. I used the 3.3 volt rail because it has a 1 amp current limit. I could charge the battery the whole amount with the 3.3 volts from my bench power supply, but it would be inefficient, could over charge the battery, and would overheat the regulator. I used the bench supply to charge the battery just enough so that the smart charger can recognize it. Warning- Do NOT do this with lithium batteries, which are more prone to catastrophic failure.
We had a similar problem with a smart lead-acid battery charger. Grandma's power wheelchair was parked in our house for over a year. The two lead acid batteries had self-discharged too low. The smart battery charger refused to charge them. New batteries would have cost at least $100. To trick the smart charger into working, we used a simple old car battery charger to raise the batteries' charge just enough for it to recognize. After that, they charge with the smart charger every time, with no issues.
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