That’s great information. I’ve always hated trying to get that smoke back inside the box!
There are some isolated DCDC converters available which would produce 30A each, so like your system, two would be needed. I don’t much care for the faililure mode you describe. As you say it’s the high voltage that would have blown up the caps (probably electrolytic or tants), and probably some IC’s would not take kindly to overvoltsge, so the fuse would do nothing.
If the same thing happened with a 24V bank being connected via failed DCDC Convertor, to a 12V battery, the first thing that would happen is high current flow, and the fuse would do its job.
The other thing I don’t like about running two DCDC converters go directly power the Icom is the possibility for conducted emission harmonics to interfere with the RF signal. The converters will run switching in the hundreds of kHz, so it doesn’t take many harmonics to start interfering with the MF band.
Your story has lent weight to the the 12V battery based solution.
I could of course install a dedicated battery, and echo charger, but the engine battery is right there begging to be used. I’d change my engine battery to a deep cycle type, but other than that it’s a simple and elegant solution.
Hmm, where’s the gotcha?