Dewalt is the only way to go. Just don't leave batteries in the charger for to long as this will reduce the life of your battery if not fry it completely. I have done this several times with my 18v Dewalt.
We use DeWalt cordless tools at work CONSTANTLY...all day long, 2 shifts, 24 hours a day...the Cordless 12v impact gun we use finally crapped out after about 8 months of non-stop use and abuse (being dropped, tossed and falling in oil)...the DeWalt drills and cordless 18v stuff we use is great, but those yellow batteries are worth the extra money...I'm going to be buying a DeWalt cordless kit online one of these days once I stop buying hemi parts, gotta replace that crappy 18v Black and Decker drill and 30 year old Black and Decker corded Sawzall (it weighs a ton, it's an old aluminum case one)...
Go Dewalt 14(lighter)-18 Batteries Interchange And When You Have 3 Drills A Sawsall,radio Charger And All The Various ,house, Shop And At The Lake Place ...4 Chargers Including The 12volt For The Cigar Liter You Are All Set Keep 4 Batteries In Rotation And They Will Replace Worn Ones At The Right Dewalt Dealers Yellow Is Good Total Investment Over 4 Years $ 390.00 Just Use Milwalkke Blades And American Bits Paperdog