While removing the car battery I noticed two thinner wires attached in parallel with the big wires.
The thin ones disappear in a cable harness with some others (black ones). This is then routed into the passenger area under the carpet to this "black box". It is attached to the floor under the passenger seat. Not sure if this is original, probably a previous owner has fitted it as an aftermarket device.
I have no clue what this is, maybe someone recognises it ? Will need to remove the seat to get access to it.

Sorry for the bad pictures, view from the front of the seat
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view from the rear of the seat
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