Porsche 928S2 1984 Negative Battery Terminal in Engine Bay

[tigertiger12]

I have a 1984 928 S2 Euro Spec (if this makes a difference here)

I am looking for a good negative / ground for my conditioner / charger.
The positive has a actual place where the charging grip can grip properly.
At the moment for the ground / negative i'm using the crossbar / crossbrace which is usually painted but the paint on mine has come away.
It's an 'okay' place but the cross bar is quite wide / thick for the grips to hold onto and on occasion has caused the charger / conditioner to disconnect.

I'm wondering if there is a batter or specific place near the positive terminal which is front left of the engine bay where I can connect the negative / ground.

if anyone has a picture also that would be really helpful.

[Waylander]

The wiper motor has a ground strap, use that