BuildCraft version: 7.99.21
Forge version:
Singleplayer or multiplayer: singleplayer
Steps to reproduce: call receivePower on buildcraft quarry with value which would overflow internal battery of the quarry. You expect it to return excess value, but you will get 0L and machine would accept value which overflow it's buffer.

On my side i fixed this as follows:

Yes, MJ is broken at the moment, but it will all be changed on the future with the MJ update.

(So I won't bother fixing this now)

...although I should probably keep this issue open until I actually release the MJ update.

API is good but implementation is a bit sad. That's the only thing you need to update.

Oh er the MJ update will change the way everything works thematically too, so the whole API is being shelved.