I finally gave up and sat down last night to figure out what was wrong with my Designshine taillight - it kept shutting off when the battery should have been charged. I put the battery on the Tenergy and it turns out the GeoManGear pack is shot. It was theoretically a very nice pack with good quality Panasonic cells in it. I grabbed a generic eBay pack that's a year or two older than that and tested, it works fine and ran my light on the way to work this morning.

I've got an 8 cell pack that I might switch to for the winter. It can run my headlight and my taillight for a week on a charge. Getting sick of charging my "name brand" (Cygolite) Metro every day.