I found a Razor electric dirt bike and figured I'd see if I could fix it.
Batteries were dead and the "control board" was dead too. It's an on and off throttle so really a relay is all that is needed, though I'll probably put in a motor controller to set max speed while I'm in there.
Now the batteries are SLA 7ah 12v batteries (two in series). I disconnected them and they were DEAD.
I figured I'd try to give them a charge and see what happened.
I got out my bench power supply, did some googling and set it to give 14.7v at a max of 2 amps.
I hooked it up and the (individual) battery was taking .3 amps at 14.7v.
I did some more googling to see that might be because of sulfation on the plates. Sure enough, as I let it sit, it started to increase in the amperage it was taking.
Now, I've put it on to charge for like 12 hours, several times over the last few days. I take it off the power supply when I leave the house for safety. I have now left it on for 24 hours and it's still taking 2 amps at 14.7v.
I'm just confused as to where this power is going.