These look interesting.
In fact, they look awfully similar to the
GAMI Supplenator which is not yet certified for anything.
I reckon GAMI are using the same generator assembly as B&C. They claim theirs works without a battery, and while GAMI did not answer a direct question on this in one forum a while ago, it seems obvious that they are modulating the field current sufficiently to generate a smooth output voltage without a battery. With a 3 phase AC generator and full wave rectification, and a decent closed loop regulator, this is completely possible.
Certifying this type of product cannot be hard, so IMHO GAMI are obviously holding back till the market is ready for their FADEC system.
What I don't understand is why aircraft makers don't simply fit 2 alternators, 2 batteries, two buses, and then have diode-fed batches of avionics. That's what the Cessna 400 does, IIRC, and it is very simple. Chance of a total electrical failure is practically zero. The extra weight is maybe 20kg.