Battery forces MacBook into sleep mode.

I repaired a friend's water-damaged MacBook. I ended up replacing virtually everything except the screen which appears to be working fine. I have replaced the Magsafe, battery, and the battery connector. If I start the MacBook without the battery it works fine. With the battery, it seems like it forces itself into sleep mode. The same thing happens if you try to plug the battery in while it's running... the hard drive immediately spins down, screen turns off and it seems to go into sleep mode. Remove the battery and back to normal.

What in the world is going on? Is this a potential logic board problem? The logic board I bought for this MacBook was factory sealed but I guess I can't rule out defects. It is worth noting that the old water damaged battery connector was used on the new logic board... I still don't know if the old battery connector was technically damaged or not... it just looked possibly corroded in some spots.