Charge adapter D batteries

thingiverse

I discovered two rechargeable NiMH D batteries for a project, but I only had a small AA-AAA charger available. I wondered if this Rayovac AA charger would charge the bigger Ds. Yes it will. My Energizer batteries are rated at 1.2 volts and 2,200 milliampere-hours. After being stored for a year, their initial voltages began at 1.20 and 1.21 volts. I plugged them in for a couple of hours, and the voltage is now 1.42 volts. The batteries are not even warm to the touch. I think a D has eight times the capacity of an AA, so charging this way may take some time. (Six hours later, I returned to find that the light was off. After cooling, the final voltage reached 1.41). I was curious about how to accomplish it, so I designed an adapter in two parts to give me options. The upper and lower sections were eventually hot-melt glued together, but might be friction welded or glued, or perhaps modified and printed as a single piece? https://www.thingiverse.com/thing:1807093 (welding) As for electrical connections, I chose stranded wire and poked holes where needed. A touch of solder can help make electrical contact. The heat also melts and secures the wire to the plastic body. Strips of heavy aluminum foil might work as well. Whatever is used, the connections to the charger should be tight and reliable. All these chargers are slightly different, and you may need to modify this design or create your own custom adapter. However, I believe any AA charger will charge larger C and D batteries. The print time on an Afinia H479 was 1 hour and 30 minutes with 0.3 millimeter layers, medium fill, medium speed, and a raft. The material used was 38.5 grams of ABS. These files are in inches. If your software thinks the STLs are metric due to impossibly tiny shapes, simply scale them up by a factor of 25.4 (in X, Y, and Z), and everything will be fine.