Makita battery Makita batteries flash red and green.

charging steady red then flashing red overheating and green red flashing replace battery.

Makita chargers are designed to check a battery before charging them. If both the red and green lights are flashing after you put a battery on the charger, it is reading a problem with the battery and will not charge it. It could be a bad cell, a problem with the circuit board, etc. but as long as it reads the problem it will not charge the battery.

The pcb inside the battery has a microcontroller that monitor the charges and charge cycle. When the cell falls below a certain voltage, it will instruct the charger not to charge and will show with a red-green flashing light. If the battery has been tried 3 times in succession then the pcb will brick itself from the makita charger. So first replace the bad cells. There are 2 solutions at this moment: charge with a 3rd party lithium charger like the imax b6 or replace the pcb with a working one. check out my blog on http://mkbl1830.blogspot.com/

Alternate Red and Green flashing means bad battery. Buy a new one, or take it to a Makita Service center for replacement if it's under warranty.

Normally the yellow light indicates hot battery, but it could also mean dirty battery contacts so the heat sensor can't be read, or that the fan is clogged with dust and unable to cool the battery. The manual says let the battery cool and try again. If the yellow still flashes, it's contacts or the fan.

Read the manual online at:
http://www.makita.ca/data/upload/accessorypbim/417_im_english.pdf

Your battery is shot. $75 - $100 for a new one.

on my charger (DC18SC) alternating red and green dual flashes mean a defective battery.
http://ubermanuals.com/product/makita-dc18sc-8866 also same for the DC24SA

unplug charger to let it reset. plug back in and then try again, if it still flashes red/green that would indicate a battery failure. check for warranty replacement.

i have had the same problem with red and green flashing on my makita charger --- cleaned the contacts blew out the fan problem solved

hey
flashing orange=cooling abnormality.
you need to wait for the battery to cool.

see my mod page, it has all light explanations in it.
Have fun
Avi