Remember to stop using a battery as soon as you detect your tool beginning to slow down. The higher the pack voltage the more critical this is. If you take it all the way down so the tool stalls you are virtually guaranteed to be reverse charging (and thus damaging) at least one cell.
Went to the local Borg to pick up a 2 x 4 and while there I took a quick look to price a replacement 18V. De Walt battery since I have one that needs a rebuild. Sure enough, there are the 18V XRP batteries on the display tagged @ $119.00. next hook over are 2 packs priced $99.00 each, (was $179.00). Took a 2 pack to the check out and sure enough it went through for $99.00. Best price I've seen for rebuild is $58.00. Gerry :-)} London, Canada