Need A Product To Test Electronic Items Such As Stereo Head Units. Pro

[pete rock]

hello to all the experts i have a kind of odd question and dont know where to post it so ill take a shot here.i sometimes pruchase electronic items such as car stereos cd dvd players and want to test them before selling them to anyone.just want to test the power functions and such.meaning hooking up the power and ground wires to get the unit to light up.not sure exactly what i can purchase to get this to happen.i was looking at a rayovac 12 volt battery with screw terminals someone told me this would probally work but not sure. the stereos i purchase usually say 12v on the top sticker.would this work for what im trying to do to test them??

heres an example of what i mean:

http://cgi.ebay.com/12-volt-Lantern-Batter...id=p3286.c0.m14

please everyone any and all help would be greatly appreciated thank you