I have gone through 4 Superstart batteries the last couple of months. I noticed my cranking and deep cycle were sizzling as I put them on the charger. Noticed one of the batteries were slightly leaking acid and took both of them back to OReilys to tell them what was happening as I was charging the batteries. They plugged them in and said they heard the same thing. Replaced both batteries and I had them test my charger(Ranger Dual Pro) and it was only pushing 2 amps like its suppose to. Get my two new batteries and they're doing the same thing. Exchanged the deep cycle again but this time for a pro series deep cycle battery. I tried plugging them into another charger and slightly heard a sizzle but not as bad. Is it normal to hear a slight sizzle in a battery while charging? Surely I couldn't have bought 5 bad batteries...they've made this noise on two different chargers albeit not as bad as the dual pro. Is my dual pro charger bad now? I can't find an answer from anyone. Any help would be appreciated!