Hi!
-Place two batboxes in series with some cable between
-Lock the second batbox's output with redstone or a lever
-Connect a third (empty) batbox after the second.
-Fully fill the second with 40k EU
-Put some power in the first batbox and watch it slowly empty itself
Cables used: insulated copper cable
Tested in SMP with following mods installed:
Rei'sminimap 2.8_04, BC 2.2.8, Power converters 1.3.0, Railcraft 2.0.2
Managed to get it working by using a cable splitter as a switch instead of the batbox.
Thanks for this great mod, by the way. It's awesome! Can't enjoy MC without it anymore.