Rebuilding makita battery instructions

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: 18v Lithuim Ion battery will not 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 + (tip end) 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: dc1804f charger

If you have tried discharging the batteries prior to charging them already with no result and from what you describe in your post, then I would have to say the charger has issues. Go to HD or Lowes (not sure if Lowes carry Makita) but another charger and test your battery again. If you get the same fault, there is an issue other than the charger, if not you need a new charger anyway. If you get the same fault with the new charger, you can always return the new one. Short of opening up the charger and using a volt meter, this is the easiest way to test to pinpoint the real problem. I hope this helps and good luck!

SOURCE: Brand new Makita DC18RA charger wont charge the batteries.

Return to store for replacement.

SOURCE: nicad battery for makita want charge

For NiCd and NiMH batteries - check the battery voltage (for a good battery it is ~ 19, V); each battery contains 15 units 1.2 V each; you can test each unit after disassembling the battery case (my have 4 screws each, and the case has bottom and top parts). First charge the batteries; second, disassemble cases and check each unit voltage (shouldn't be less than 1.2 V); then take any battery tester (for AA, AAA and other batteries and accus for home usage), attach 2 long (~10 inches) wires to tester's testing contacts, and test each 1.2V unit for current - if it is in "yellow" or "red" zone - the unit is dead and needs replacement