Get a 1/2" Cordless Impact Wrench at Amazon (links below) :

Dewalt DCF899 - http://www.amazon.com/DEWALT-DCF899HP2-Brushless-Torque-Impact/dp/B00FREST98/?_encoding=UTF8&tag=reatoorev-20

Milwaukee 2763 - http://www.amazon.com/Milwaukee-Electric-Tool-2763-22-Impact/dp/B00GFUA7FC/?_encoding=UTF8&tag=reatoorev-20

Ingersoll Rand W7150 - http://www.amazon.com/Ingersoll-W7150-K2-High-Torque-Impactool-Batteries/dp/B006GFQMAU/?_encoding=UTF8&tag=reatoorev-20