Would be nice if there was a piece of kit out there that you could put your batteries in, like a charger, that could give you some insight into the state of the battery and whether or not it was close to failure or if it was good to go. Coming from an electrical background however, I don't think such a thing is possible but maybe by discharging and measuring voltage decay, it might be possible to determine if your battery is getting too old? Any thoughts? Could be a good business venture if such a device could be manufactured.