I put the battery charger on my Turbo Start batteries today. They are the old style that you have to put the acid in. They are 4 yrs old. When I'm not racing, I charge them fully once a month. Well today I starting charging them right after lunch. I want to say the gage on the charger showed about 10 which is normal for when the batteries have been sitting w/o use. The next time I looked it was showing 15 ( 0 is fully charged). I came back in the shop a couple of hrs later & smelled something. So I took a look at the batteries & it was them. They were hot & had puked up some acid into the little vent jug. The charger was still showing 15. So I cut the charger off & disconnected the batteries. So I don't know how to check a 16V battery. I have a 12V battery tester but that don't do me much good. Could it be a charger problem? I'm just wondering if after 4 yrs the batteries have gone bad. Any suggestions?