Years ago in a fit of tree-hugging self congratulations, I junked my outboard engine and converted my little boat to electric. It runs on 36v from three 12v Lead/acid deep cycle marine batteries.
Since that time I have been charging the batteries with individual Schumacher 12v chargers. Which burned out, starting with the newest one, of course.
I had some beefy transformers from old UPS units, so I decided to build a 36 volt charger. These transformers only made about 32 volts, and so I decided to rewind one.
To do that I stripped down the laminated core into hundreds of bits. The first ones are removed with a tap hammer and bar. After that it’s just paint holding the core together.
Here’s the core before rewinding. There’s 4 different coils of wire, and two were not needed at all. I added 8 secondary windings to raise the output voltage.
It was a mistake. When I tested it I thought the voltage was way too high, and I disassembled the transformer again to remove them. Just removing the two unneeded extra coils somehow got me what I needed without additional wraps.
Here is my test rig on the bench after rewinding. The rectifier circuit was modified from a Skil drill charger, which was only 9 volts. I stripped it down to just a full-wave diode bridge.
Here it is in the boat, cranking out 47.48 volts into 3 rv batteries, from just 2.9 amps @ 121.2vac. They have been on about 1 minute. These batteries haven’t been charged in about 50 to 60 days.
This did a fast job. It was stronger, faster, ran cooler, and was better than expected. I was well pleased that I got this right on the second try.
Now I need to really discharge the batteries, and give it a real test.
Since that time I have been charging the batteries with individual Schumacher 12v chargers. Which burned out, starting with the newest one, of course.
I had some beefy transformers from old UPS units, so I decided to build a 36 volt charger. These transformers only made about 32 volts, and so I decided to rewind one.
To do that I stripped down the laminated core into hundreds of bits. The first ones are removed with a tap hammer and bar. After that it’s just paint holding the core together.
Here’s the core before rewinding. There’s 4 different coils of wire, and two were not needed at all. I added 8 secondary windings to raise the output voltage.
It was a mistake. When I tested it I thought the voltage was way too high, and I disassembled the transformer again to remove them. Just removing the two unneeded extra coils somehow got me what I needed without additional wraps.
Here is my test rig on the bench after rewinding. The rectifier circuit was modified from a Skil drill charger, which was only 9 volts. I stripped it down to just a full-wave diode bridge.
Here it is in the boat, cranking out 47.48 volts into 3 rv batteries, from just 2.9 amps @ 121.2vac. They have been on about 1 minute. These batteries haven’t been charged in about 50 to 60 days.
This did a fast job. It was stronger, faster, ran cooler, and was better than expected. I was well pleased that I got this right on the second try.
Now I need to really discharge the batteries, and give it a real test.