Charging / Battery Issue

Basically i had a very corroded board after a friend water spill when i bought it for £500 the week before, im determined to fix it.

Managed to pick up another identical model for free which had its own problems.

so far i have replaced.. Mobo, HDD, Battery, Ram, Dc-in (twice), sata cable for HDD, & ribbon cable for battery sensor lights.

Its still not recognizing the hard drive as i was having mount problems but my main issue is with the battery.

problems..

the macbook will power on if battery has been charged in another model but cannot take charge itself or run off ac power.

X where battery icon should be, it also says

"power source - battery

battery not available" - or something to that effect.

it will not charge what so ever, occasionally when magsafe has just been plugged into another macbook it will mimic the bright orange or green light for a minute or two and then dim.

battery works fine in other models, tried all resets.

charger works fine.

new mobo + charger + dc-in + battery - wtf?

im completely out of ideas at this point. it has no OS due to the fact it cant find the hard drive currently, that surely cant be affecting battery/charge, can it?