Please help! I procured an electric wheelchair today (worn and torn, but in good shape. It had 2 12v batteries, little smaller than an auto batt. Didn't write down the amperage tho...The batteries were visually inspected for bowed or expanded sides, cracks, oxidation. Everything appeared in order. They have likely been sitting for some time. Stupidly, I did not check electrolyte levels. Oops. Could easily be low. I plugged the charger into the mainboard for 30 minutes, watching closely. No issues, no overheating. I left it for another 2 hours. Again, no noticeable issues. I tested the drive motors by controlling it around my driveway briefly. Power was very low. It worked, but clearly lacked juice. I plugged the batts in for another 4 or 5 hours. But after that time, I noticed a crackling/squealing (faint) sound. As if pressure was escaping. Bad news. I had the chair chassis (and batts) in my workshop, and now I was afraid it may blow, contaminating everything. The batteries feel warm. One more than the other. Beginning to panic, I threw on my goretex, respirator, goggles and gloves and carefully detached the battery cable from the main board. I've never had one of this size blow, and have no idea what it could do. very hesitantly, I rolled it into my garage, and closed the door. Now I'm afraid to sleep, because I'm concerned about it. Is this Normal old battery behavior? Could this be due to low electrolytes? A small crack in the case? Is there anything I can do besides wait? I'm not real anxious to go too close for too long. Is there anything I can do that would not increase hazard? I'm about to throw a tarp over it, but is there a high flammability risk if a high amperage 12v were to blow? Guidance highly appreciated. Thank you.