What is this black box?

[Scrump]

I replaced the starter battery in my van and found this black box tucked down the side of the battery
It had small gauge wire running to it straight from the +ve and -ve terminals. There was no wire attached to the third connector on the box.
I did wonder if it was some form of split charge relay for the leisure batteries but cannot see it is the relevant connections for this (plus the van has had a proper dc to dc charger since it was built when new).
It has no writing or other marks on it except a handwritten sticker saying 12v.
Any ideas?

[Chris32345]

Any marker mark or numbers on it!


What was the wiring like did it look factory or after markket?

[Caddyshack]

Open it up and have a look inside, I am guessing something like a split charge relay but it does seem odd with 3 terminals. The 2 look pretty chunky as well.

[Scrump]

Chris32345 said:

Any marker mark or numbers on it!


What was the wiring like did it look factory or after markket?

No marks or numbers on it at all (apart from 12v sticker)
Wiring was definitely aftermarket.

[Scrump]

Caddyshack said:

Open it up and have a look inside, I am guessing something like a split charge relay but it does seem odd with 3 terminals. The 2 look pretty chunky as well.

I agree, can’t see it now it would work as split change relay. It has two chunky male spade connections and one small male connector. The wires connecting it to the battery terminals were not large to take enough current to charge another battery.

[Polly Grigora]

Guessing though

[Scrump]

I have removed the top of the box, the plastic plate around the spade connectors and there is another small one under there which has been removed (no hole for it in the top cover).
So it does look like a large relay, I think it may have been for split charge relay or similar but doesn’t seem to be needed now.
I will stick it in the glovebox for now, but the van seems to be suffering no ill effects after the box was removed.