Mercury cell hearing aid batteries can be charged with this "D" cell battery booster if hearing aid batteries are not completely dead. We drain current from high capacity battery into smaller mercury cell.
With batteries positive to positive held by bent wire (like 3/32 inch brass or bronze brazing wire) to hold batteries together with ends of bent wire in hooks to clamp on bottom of larger D cell negative terminal and make contact with negative terminal of hearing aid battery.
Use hearing aid batteries for one day then charge 4 hours with this charger. Use other two hearing aid batteries next day so you rotate battery use to every other day.
If slight hum or whistle after charging set the cell aside for a few hours and then it should work okay.
After two months start with all new batteries.
The two 1 micro ohm resistors are to run in simulator.
