I have a new old stock battery that I decided to put into service. This battery has been in dry storage for thirty years, that is correct, thirty years. Anyway I added acid on Saturday and then attached my battery tender to top off the charge. The battery tender never was able to top charge the battery and go into float maintenance. I decided to charge the battery with my regular battery charger. When I placed the charge cables on the battery, sparks flew. The cable placement was correct for the terminal, positive to positive, negative to negative (verified for the battery tender and the regular charger). I got my volt meter and discovered that the polarity was reversed. I never had this happen before. This evidently occurred when the acid started to activate the plates. Research indicates that a lead acid battery can be reversed charged and it is possible to correct the situation by discharging the battery and then recharging the battery correctly. I currently have a headlight on the battery. Has anyone seen this problem and were you able to reverse polarity. Glad I didn't place this battery into the car, I now would have a major electrical repair.