Discharge capacitor on inverter (sparks )

Im upgrading the cables that connect from my AIO inverter to my battery. The AIO cables have sparked before when they touched when I was transporting the AIO inverter.

Is there a proper way to discharge the AIO or is this spark harmless? Should I touch the +/- on the AIO cables to spark and discharge the AIO capacitor or should just I connect them to the battery +/- terminals, will this spark too or cause damage?