I lent out my cordless makita drill that uses the 9000 battery. When it drained, my friend plugged the charger into 240v instead of using a transformer to bring it to 110v. What are my options.

Generally, When your have the 18V milwaukee drill, you had better to use the same voltage battery charger to charge the battery. it will be more safe.
John.
http://www.anybatteries.com.au/battery-model.php/Power-Tools-Battery_milwaukee.html

Replacement MAKITA 6391D battery pack 100% compatible with the original 6391D battery, high quality, wholesale price.

http://www.drillbattery.com.au/buybattery.php/makita_6391D_power+tool+battery.html

Hi,
It sounds like the problem is the battery. It sounds like there are shorted cells in it so that it starts to draw too much current from the charger and the charger shuts down as a safety measure.
I hope this helps,
Happy New Year,
Mark

The battery could be bad after 5 years. Check the contacts on the charger with it plugged up using a volt meter to see if it's putting out.

Check the speed control. There is a speed control usually from hi to low... sounds like it's in between speeds... try adjusting it back and forth...
It should go back into one gear and work fine.

As long as the charger voltage and the battery voltage match (7 volts) there should be no problem. A fast charger just runs more current thru the battery (per unit time) than a not-so-fast charger. If you notice the battery getting really hot when it's charging (like too hot to touch), stop using it.

Unfortunately, Makita’s li-ion battery packs have a design flaw. After having the same problem with my two batteries, I took it apart and saw the problem immediately. You see each battery pack has ten li-ion battery cells and a circuit board with a memory chip witch holds the charging history of the battery pack. But that memory chip constantly draws power from 2 of the 10 batteries. The current it draws is very small but if you consider it over 8 month or more, the power drain becomes very significant. You end up with a battery pack with 8 still fully charged battery cells and 2 drained battery cells. When you put this battery pack in the charger, it detects weak battery cells, assumes they are defective and refuses to charge. To avoid this problem you should charge your battery pack often, even if you haven't used it, every two months should be ok.
I suspect that Makita doesn’t make these battery packs, they make power tools, good ones too. Buy Makita should definitely have a few words with their supplier before they become a liability!

of course

Don't go buying more stuff when you can fix the problem yourself without buying any converter. The modification required to do it is very easy and most people wont have any problem following it.

You can go to this webpage where a detailed walkthrough is given (with pictures):
http://www.byggebolig.no/index.php?topic=5572.0

Some of the post are in norwegian but the walkthrough is in english.

Good luck and happy moding :)

P.S.

For those of you that have "blowed up" a makita charger 110v on a 220v, don't throw it away!
If you are lucky you have only blowed up the fuse and the varistor, which are easy to replace, and if you follow up the walkthrough you might even go all the way a mod the charger to 220v.

I know, I have already manage to "save" a blowed up charger.