This is a great battery, not many complaints here, but....the four stars are because they do have a design flaw that make them fail prematurely.
If you use it for some time and then leave it uncharged for a long time (it doesn't have to be that long, 3 weeks will do it) then the sensor on the battery will stop working and you wont be able to charge it again (you wont get much advance warning).
Now the good news, if the battery really failed prematurely and not because it was its time (lots of charges/old etc) just ship it back to makita and after scaning the battery for number of charges THEY WILL REPLACE IT FOR FREE!!!!