Engine starting battery being charged while parked?

Some do, some don't. Ours is supposed to but I don't think it's working. Ours as most do has an engine battery disconnect switch that I turn off when parked.

There is also a switch that allows to temporarily tie the house batteries to the engine battery to start the engine in an emergency. And if all else fails, I carry jumper cables long enough to connect the house to the engine battery