Building a deck today with my mate John, who is a hard working intelligent chap - with no knowledge of power tools at all.
Using a 12v Makita impact driver & a 14:4v Makita drill driver - which share the same charger.
Spotted that John had inserted a 12v battery into the 14:4v driver - only used for a short while apparently. I was surprised it fitted, but it did.
Question. Would this have damaged the 12v battery or the 14:4v driver at all?