Hi guys, I recently set up a LED lamp above my lathe, it required 12v. I had a spare 12v gel cell battery looking for a purpose, so I hooked it up. Nice bright light with it's own on/off switch. I added a small plug pack charger, 1 amp, and capable of floating when fully charged. I also intend to run a few more low power items off this setup. After a couple of hours running I switched it off and retired for the night. The next day I went to switch it on and the light didn't work, put multimeter on battery = 12.5v ? assuming the new light fitting was faulty I took it down and pulled it apart, Another similar battery was on the workbench so I touched the light wires to it and presto it worked. Went back to the original battery, wouldn't work? checked battery again 12.5v? take a second look at meter -12.5v switched the meter leads around and got+12.5v. hooked up the led light wrong way around, yes it worked. ???? The two batteries are identical 12v gel cells about 2 years old, now one of them suddenly decides to switch polarity, overnight with every thing turned off. Any clues gentlemen, and ladies? Can I get the polarity to switch back, or can it be used like this.????