Bumstead I am no expert, but I have read several times in articles and such that the batteries will not try and charge each other.

Ramduster be sure to check out the rcbattery clinic website, it has lots of good info and addresses your question.

The RC battery clinic webpage http://www.rcbatteryclinic.com/ says

¨Many pseudo battery "experts" put forth the argument that plugging two battery packs into the same receiver with out blocking diodes is NOT a good thing, claiming that his creates a host of problems and the two packs will end up fighting each other or "cross charging".

These concerns show a lack in the understanding of the charge and discharge potentials involved in Ni-Cd cells. One pack cannot charge the another (equal number of cells) as the discharge voltage of a pack can never be as high as the voltage required to charge the other pack.¨

From what I hear here on RCU "Red" Scholefield is one of THE authorities on RC batteries.