Post by FrankenMech on Mar 15, 2015 14:14:39 GMT -5
I made a battery 'maintenance' charger from an old Ryobi 12V tool battery charger. It was 15VDC @ 200ma wall wart. One of those black or white box like things that plugs into the wall outlet. I just connected the wires to the ones I used for my old battery charger that plug into the 12V power outlet I mounted on the scoot. I added a couple 3A diodes in series to the lines to bring the max charge voltage for the scoot battery down a bit. It should be 13.8-14.2VDC when fully charged. Many of us may have wall warts for old tools and devices hanging around. I never throw away any of those wall warts. I think I have 5 of them in use around the place being used to eliminate the need for batteries in devices etc.
It will soon be spring garage sale time and I will acquire a few more for 25-50cents each. I have a bunch of 12VDC units but not so many of other voltages. They come in useful and voltages can be adjusted down with a few diodes. Diodes are not something I find at garage sales but they are dirt cheap if purchased in quantity through fleabay or Amazon. Look for 1, 3, or 10A in 400V or above. Always derate the diode by at least two and don't use them fully loaded to their specs. The specs are always done in some sort of super lab conditions and don't have any relation to reality in the field. Full wave rectifiers can be used with AC output units. I usually just epoxy them to the outside of the wart. Make my connections, and cover the connections with hot melt glue. Derate the full wave rectifiers by four.
Larger capacity chargers like 1A or 1.5A can be made from larger wall warts. Even some of the 12VDC 1A wall warts can be used to bring a battery up then finish it off with a small 200ma charger like I made above. It just means a little experimentation and stopping at those garage sales.
Some wall wart charger systems have multiple output voltages.
Don't be skeptical of size. Older wall warts were made with transformers and linear power supplies. Many of the newer units are much smaller for a given output because they use switch-mode power supplies. They may not be as robust as the older units. Watch for rising temperatures in whatever supply you play with. Heat is the enemy of electronics and usually means some component is overloaded. Overloaded components can let the magic smoke out. The little wall warts shouldn't go up in flames but we can't ASSUME that.