Suggest turn the peak detect down to 0 to 5mV, your probably getting the batt too hot. Sadly the 3550 might be all your going to get, especially if you have charged at 10mV several times. High capacity nimh tend to degrade fairly fast unless they are very well taken care of, equalized and such, and good cells that are well matched to begin with. One of the reasons us average Joes love lipos.