So I have a Makita 1850 battery that says it's broken when I put it in the charger. But when I took it apart all voltage and connections are good. Any ideas were i can get a new circuit board or how I would test the board?

SOURCE: Vtech 8L55 2 unit portable phone

I just had the same problem. Could be dirty terminals. I took the battery out, cleaned the terminals on the battery and phone with a pencil eraser, put the battery back in and it's working fine. (Says fully charged, where just a few minutes ago it said low battery).

SOURCE: Food processor circuit board fried ?

Sir,
It's no use when a lighting gets in the circuit... it fries everything... board replacement is a good option but where to get it is the most difficult part... Try a junk shop, or the repair shop, or to a neighbor, or the stores, they might have a board just like yours, damaged item but not the board... I hope this helps.

Fixya me on this .... Goodluck...

SOURCE: makita dc1804f charger will not charge new i-mh 1834 18v battery

I think your tryiong to charge NIMH batteries oon a charger designed for Lithium Ion batteries. With all the new style batteries such as NICAD, NIMH and LI-ION, charging becomes difficult. Most chargers pre NIMH and LI-ion, were designed for NICAD's. The best advise, match your batteries with the correct charger

SOURCE: Makita 18v Lithium-Ion BL1830 Battery Won't Charge

If you have been a bad boy and managed to short the battery by using it for non-proscribed purposes, the fusible link will blow (kind of like a fuse) To fix it, open up the battery (use a Torx 10 security bit, or a small flathead in a pinch) On the battery connection nearest the spring-loaded white catch there is a small bridge of metal with a hole in the center. If this is melted you can solder it back together by sanding the two pieces and putting a glob of solder on them. This will void your warranty (duh!) and remove the battery's fuse protection, but it WILL work again. If the link is intact and nothing else is obviously wrong, you almost certainly have a bad cell. I recommend pulling out the bad cell ( it will be the one that does not read between 2.5 - 4 vdc) and replacing it with one from another dud battery- this requires some fudging and re-soldering. Or do what I did, pull the cell, toss the electronics and the short pink wire, add a cigarette lighter socket and voila! you have a portable power supply giving around 14 volts. Charge it up by wiring two cigarette lighter male ends together (check polarity , + to + and - to -) and plug it into your car, but only while it is running or you will be charging your car battery with it! Hope that helps.
Matt Binns GiantGlobes.com

SOURCE: Have Makita drill with DC18 RA charger. Blinks

The Makita Factory may repair them, and then resell them in reconditioned kits, but they will only sell you a new one, or replace it under warranty.