What you want to stay away from is any brand were the battery is charged from some plug in pin and the transformer plugs into the wall....THESE ARE CRAP AND CHEAP AS HELL. Those type batteries will maybe last a year. Get a nice unit that has a nice quik charger were the battery plugs into a charger base and no little box plug that goes into the wall. I have a home model Makita, not a construction line model, but the batteries and charger base are the same. It's a great drill for around the house and small projects. I went thru two Firestorms(cheap) and a Craftsmans(18.8v) that had the cheap charger and batteries. I believe I paid around $110(eBay) for my Makita setup, two batteries and a flex lamp and case. If you're not using it for daily work purposes, a good home version will work fine.

Here's a 1/2" home version
http://cgi.ebay.com/MAKITA-14-4-v-1...Z007QQcategoryZ82265QQrdZ1QQcmdZViewItem

Here's a 3/8" home version
http://cgi.ebay.com/MAKITA-14-4-VOL...Z006QQcategoryZ28057QQrdZ1QQcmdZViewItem

I couldn't find a 1/2" construction version listed. They have alot more aluminum built into their housing and much heavier..

Also, keep your batteries out of the heat. Heat kills batteries