Foild drive assist plus battery connector

A friend of mine just got a foil drive assist plus and I checked out the battery connector which has a curious 3 wire connection. I surmise that this 3rd smaller wire is simply to indicate to the battery side balancing circuity that the unit is in charge mode. I can’t be sure about this though. Next time I’ll check what voltage I get on the those two tiny pins in the connector. Does anybody know for sure how it works ?

The smaller pins are to prevent spark when connecting the battery.

Are you certain about that ? Typically anti-spark plugs do not use a separate wire back to the battery to achieve it. In other models of plugs those extra pins are referred to as separate signal wires.

Looks like it’s a XT90I-F connector in your picture. They have a total of 4 wires compared to a more common XT90 which has 2. The anti spark XT90 has a green on yellow plastic covering.
How Foildrive implemented it is likely proprietary to them so you might not get a definitive answer but seems reasonable that the small leads go to the BMS.

Maybe the small pins are for charging and go to the BMS? And the large pins would be for discharge only.
Just a guess.

I just probed a charger connector and the two signal pins on the charger side are shorted together which could be detected by the battery side charge circuitry.