Ok I see.
buy the way I disconnect those few time no problem.
I use a big screw driver from above on the slots of the negative.
I hope u didn't try to hold it from above and open the nut from below lol it's a one part.
No I didn't. I thought not to bend the connector with screwdriver so I went with pliers from down without screwdriver. I don't like to work on visible parts pliers only comes close to invisible parts.

