I've got six NiMH rechargeable AA batteries, all the same brand and rated capacity, a one-hour charger, and a flashlight that takes two AA batteries.
I wanted to see how long the light would last on a fully charged pair of batteries, so I charged up a pair, put them in, and turned it on. I got
5 hours of good light, and another hour of feeble light.Next pair: *one* hour.
Third pair: 5 hours.
Now for the interesting part. When I put the bad pair in the charger (which is one of the chargers that does each battery individually), one of them finishes very quickly (five minutes, tops). This is repeatable (i.e., that pair has a short life in the flashlight again, and one finishes charging quickly again).
It seems to me I should be able to deduce something from this, such as that one of the short lasting pair is defective...but I'm not sure *which* one.
Let's call the one that finishes charging quickly battery X, and the other battery Y. I don't know enough about how these things work to tell the following two scenarios apart:
- Battery X is defective. It somehow makes Y provide all the energy, and the light stops when Y is discharged. X hasn't provided much energy, so recharges quickly.
- Battery Y is defective. It rapidly discharges, then acts as a high resistence, stopping the light. X recharges rapidly because it hasn't been asked to provide much energy.
I'll now try each of these batteries with one from one of the good pairs. Presumably, one of X and Y will play nicely with batteries from the other pairs, and one will not, and that one that doesn't is the defective battery. However, I'm curious...should I be able to tell just from what I see at the charger which of X and Y is the bad battery?