The days of the hand powered knock out punch are numbered. Many companies are now coming out with powered knockout units. It is easy for the big brands to do as they already have half of the battle won with the batteries. Battery technology is a huge part of the tool and if you have some cheap no name batteries you will be having issues.
GreenLee went to the proven Makita battery platform to power their latest knockout tool. Makita batteries are everywhere and have a good proven track record of being a solid battery platform. It weighs 4.2 lbs and has a 360 degree rotating head to get into the tightest of spots. The unit can punch up to 6″ holes. The tool is available online for roughly $1300. Check out GreenLee for more.