Its actually a motorcycle battery but don't think its any different than a car battery. Anyway, its about three years old and I have it hooked up to a battery tender for the winter. About three weeks ago I started my bike with no problem. Last week I tried to start it and the battery was too weak to crank over. I checked the voltage and it reads 13.2V but when I crank it, it only reads a little over 3V. It doesn't matter how long I charge it the outcome is the same. I also bump started my bike and the alternator was supposed to be charging it. Why is it not able to hold a charge? Did my battery tender damaged it? Its one of those sealed ones and I can't see the fluid level.