JD, I talked to Geoff last year about adding a new, third battery to my two existing 300's and he said that they indeed don't play well together. I couldn't tell you why as it's over my head. But he did tell me if I added a third battery I should only use it and not the other two until I cycle the new one through 20 - 30 charge cycles and then all should behave. But my disclaimer is to talk to Geoff. I'm not totally sure of the number of charge cycles. See you tomorrow :)
John