The Makita DC18RA is a rapid charger for Makita lithium ion battery packs; it fully recharges batteries in 30 minutes, according to Makita. If you find that you're charger won't charge your batteries you need to determine if it's the charger or the battery. Unfortunately, Makita DC18RA chargers don't contain user-serviceable parts, but you can try some troubleshooting steps before returning the charger to the store, as you may be able to get it charging again.
Put your battery in the Makita DC18RA charger. Turn on the charger.
Check if the green and red lights on the Makita charger are flashing. If they are, your charger is trying to charge the battery, but the battery can't take the charge so the battery needs replacing.
Check if the green lights are on and the red lights are off. If this is the case then the charger is operating, but there's no connection between the charger and the battery. Check that the battery is inserted correctly. Remove it and reinsert it. If the green lights are on and the red lights are off, this signifies faulty terminal connections from the charger or the battery. Try another battery, if you have one, or take the battery and charger to an electrical store so the store can test which item is faulty.
Check the plug fuse if the green lights on the Makita charger aren't on. This means the charger isn't producing electricity to charge the battery.
Remove the plug from the wall socket. Remove the fuse from the base of the plug. Lift off the fuse cover using your fingers then pull out the fuse. Put in a replacement fuse; it must use the same ampere rating. Replace the fuse cover.
Replace the plug in the wall socket. Turn on the charger. If the red and green lights are on then your charger is working and charging your battery. If no lights are on you need to take the Makita charger back to the store.