by Richard Lewis
Today, I'll be showing you how to make an updated model of my desulfator and charger that you see in my windmill book. This version is nice because it has a pluggin for a simple digital meter and with a flip of a switch you can read the current to the battery, or battery voltage. It also has another switch for a high or low charge current setting. In the below design I used a standard spring loaded speaker wire quick connect box. I used light switches for the on/off and the hi/lo switches. I used a spdt light switch for amps/volts switch. I used a GFCI socket inside instead of an isolation transformer for safety. I also show a pair of 80 MFD capacitors for my high section charging. Actually, it parallels those along with the 24, giving me 184 MFD. That would be about 7.6 amps of charging and about 1 amp at the low setting. You can use some more capacitors in parallel, but remember to make sure your switches, wires, fuse and rectifier can handle the current. The fuse should be just under what the rectifier can handle. If you hook the battery up backwards, this fuse will blow instantly. I used 25 amps for my fuse because I had a 30 amp full wave bridge rectifier.
But it is important to have the current sensing wires connected on the inside, while the current carrying connections should be toward the outside. The sensing wires can be a small gauge but the current carrying wires should be a larger gauge, enough to carry the required amps.
This is your shunt and when you select amps on the switch above, you need to turn your meter to milivolts. A reading of 5 milivolts would indicate 5 amps for example. A reading or 8.9 mV would be 8.9 amps. When you switch back to volts, you will have to turn your meter back to the right range unless you have an autoranging one.
You can see in the picture above that I am set for volts and I'm reading the battery at 12.6 volts.
Here is the plugging on the side for plugging in your meter. It is meant for speaker wires but it works great for this application.