Posted by Sherman in Idaho [72.47.153.28] on Monday, March 31, 2014 at 12:14:20 :
In Reply to: OT Battery Chargers help me choose posted by John in Utah [166.70.201.2] on Monday, March 31, 2014 at 10:46:17 :
I've gotta say I don't have the patience for any "automatic" battery charger after ending up with two totally-adjustable totally manual ones in a surplus lot once. All they have inside them is a transformer, a variac, a rectifier, a hi/lo range switch and an amp meter and volt meter. What I like is that I can decide how much current I want to put into the battery and I can decide when I think it's charged enough. On the low range, they're smoothly adjustable from 0 to 30 volts and will put out 15 amps all day. On the high range, the voltage is double and the amps are half.
A lot of times I'll resurrect a "dead" battery that won't take a charge on a normal charger. I'll crank the voltage up to whatever it takes, which could be 30-40 volts, until it starts charging, and then back off until it stabilizes. If I'm in a hurry, I can push it for a quick charge, and if I'm not, I can dial back to 5 amps or so and leave it at that rate for several days. I can use it to keep a 13.8 volt float charge on a group of batteries.
I also use one of them all the time for electrolytic de-rusting, where it really helps to be able to crank the voltage way up or down depending on how big the workpiece is. With nothing "electronic" inside except the rectifier, and 3 circuit breakers protecting primary and secondary, they also seem to be indestructible in terms of any sort of electrical abuse.
I have no idea what they cost new or where you'd buy them, but if you run across one surplus or at a flea market, pick it up.
Follow Ups: