Crap, had another one fizzle out this week, just without the cool "pop" the last one had. It was in the other crawler pack (the one I thought was still good), and voltage just started dropping from 8.5v during a fairly gentle 3.5a charge. Sure enough, I checked the different cells and one was at .2v and refused to do anything but drop more under charge.

Here's the odd thing, both of the cells that died were in the same location, as far as the pack was built. I had 2 cells taped/shrink wrapped together on the front axle, with a lead running to the back axle and a third cell. The two front cells were connected on the back end with copper braid soldered to the ends, with one having a 4mm gold plug soldered straight to it and the other with one end of the long 3rd cell's lead. Here's the thing, both times, it was the cell with the plug soldered to the end.....could they have been overheated and weakened somehow? I didn't think I heated them up too much when soldering, but I guess it's possible. From now on, I'll try to use a wire lead to the plug instead, just to be sure.