My makita 18v 2.0 battery won't keep a charge makita 2.0AH battery showing charged on charger loses charge as soon as i start drilling

according to the schematic I saw yes you can and I think that you will be pleased with its performance, their operator manual even lists the weight of tool with this battery. Makita has a 1 year limited warranty on the Li-Ion battery that you might want to consider if you have the receipt.

This isn't true because I have a second charger and it works fine

the charger should indicate when the battery is fully charger. look at the lights and they will show you. Usually though it is about an hour.

If the charge count on the batteries is under 300, Makita will replace them. Makita has a known defect in this battery that causes the battery to shut down before it is dead. So as of now they are exchanging ones with low use.

If they are truly defective and makita won't replace, you have to open them, find the dead cell or blown fuse, and replace. Search youtube makita battery for a video on repairing this battery. But once the red and green lights on the charger flash, the the battery can't be charged on a Makita charger -- it's been locked. So use a third party charger.

Sorry Mate your battery is dead...
The makita lithium batterys dont like getting worked hard quickly.
There is a chip in them that recognice each battery to each specific charger. Try another charger. This has not worked for me. Try anyway

your batteries are toast;must replace

looks to me like a defective batterie

make sure the charger is cold or keep it in a cold place, when makitas charges get hot, they will not charge.

Battery has to be cool before you put in charger,also check contacts for dirt etc..cheers

How old is the battery?
They have a service life and require replacing after they no longer hold a charge. This could be 2 years or 8 years depending on how often it is used and how regularly it is charged etc.

If it is a new battery, then take it back as it could be defective.

Possibly could also be the charger but you could verify that by charging a different battery and seeing if it charges that second battery ok, or not.