It's not 5 volts, it's 5 watts. The LED bar runs on AC.
Fortunately, it looks like whoever hacked in the LED bar in seems to have saved all the important bits so you can still use regular fluorescent tubes. Consider yourself lucky! Usually the original lighting fixtures are just removed and thrown in the trash when you get the cabs from China! I FUCKING HATE IT.
For best results, remove the ugly spliced in connector, plug in the 3-pin AMP up connector (which you may or may not need to recrimp), bypass the ballast and starter, and throw in a nice LED tube.