I have makita bl1830 battery 18volt it works fine but will not charge, charger lights flash red and green therefore battery will not charge

I live in Bahrain and I purchased my brushless Makita XT248 combo kit from ebay US 110 Volts but in Bahrain we use 220 Volts from the mains so like my other 110v electronics I plugged my charger to a voltage 110-220v converter. My Makita 110V DC18RC Makita showed the battery is damaged red and green light kept on flashing. Because both my batteries were showing me the same condition I assumed that I have been ripped off by ebay seller who might have replaced new batteries with faulty ones. I didn't liked it because I spent lot of money already as the shipping from US to Bahrain by DHL was very expensive and at this stage I paid approximately 530 USD all inclusive. I read the manuals and noticed that it said never use converter so I decided to throw more money USD 120 more and I bought myself new Makita charger DC18RC 220 Volts from UK and the same batteries were charged within 20minutes with the new 220v charger.
So I concluded I received perfect set and Makita chargers will not accept the batteries if your voltage is not 100% stable as the converters are not 100% the same voltage and I think most of US buyers have this issue probably due to the reason the voltage there might not be consistent?? I don't know this but I assume this to be the reason someone from US might need to verify this for me and for the benefit of others and by going through the forms I would like to add that because the sensors and chips inside the charger recognizes 3 or more times similar condition it refuses to accept a good battery and consider it to be bad. I will be using the voltage regulator for my charger and I suggest you to use the same if you are worried about this. I will appreciate if someone can validate this and confirm what I mentioned above as I can not test the voltage in US. Thank you, Sajid.

If the red and green lights flash, the battery might be defective, or it might just be locked due to a design bug in the battery. You can try charging it on a clone charger from eBay for $60. It that works, just use it and smile. If not, you can repair it. see my other post about that..

If both red and green lights are flashing after you put the battery on the charger, the charger is reading the battery as bad or defective and it will not charge the battery. It may be because there is a short in the battery, one of the cells is bad or the battery is just old and won't charge anymore.

Not true, my second charger works fine with the same batteries