RE: overnight charging rate for nimh batt???
To get the most out of your NiMh you need to do the forming charge. As Mr. Norton said, 0.1C for 14 to 16 hours followed by a discharge to 0.9 to 1 volt/cell at 0.25C. It may take three or four such cycles before the battery is at full capacity. It is also a good practice to redo the forming charge if the battery has been sitting for a month or two unused and, if you do much fast charging, every 20th charge or so at the 0.1C rate for 16 hours is almost sure to help.