Power Supply for SSB in 24v Boat

[Pelagic]

Hi Dockhead, we have similar set up, except main engine start batteries are 24v.
I agree with the others, best to have a radio battery as a buffer

However, instead of a separate radio battery, my 12v Gen start battery is installed in the pilothouse and fed from house bank via Victron 24/12v convertor or Gen’s alternator when running.

Being outside engine room, this single battery is kept cooler and higher same as a radio battery should, but serves dual purpose.
The DC260-12 AGM battery is same as my 24v house bank, so cranks over Gen very easily.

This sketch shows set up and radio/start battery is in locker floor just ahead of inside steering and 24-12v DC Panel.

I am told on Nets that my SSB comes thru crystal clear.

[S/V Alchemy]

Originally Posted by Lake-Effect

This what I would do, too. Alot cheaper than the DC-DC converter, and is one more battery available for 12 v loads and as a backup starting battery.

I don't think a suitable 12v battery's voltage would sag significantly on a 30A load, and I expect that any marine SSB set would be designed to cope with that anyway.

This sounds most logical to me. If you had an otherwise shot battery system, you'd want the "SSB only" battery to either start the engine or to call for assistance.

It's the same idea as I have for a windlass battery forward on a echo charge instead of forty feet (round trip) of 1 ga. or whatever I would need to wire it into the engine circuit. That's an expensive and lossy way to do it to a windlass that is also a manual. A battery (and an AGM would make sense here) that is kept at 100% through solar or wind would do well in the sort of short-burst TX that SSBs typically do. RX isn't going to use much power by comparison.

[Andina Marie]

If the 24 volt battery is used only for the SSB (and any intermittent loads) you could use the Trollbridge24. It is an automatic series/parallel switch. When 24 volts is not in use it puts the batteries in parallel so they can be charged from your 12 volt charging source(s). As soon as you draw any current from it, the batteries are put in series to give you 24 volts. It will handle charging sources up to 100 amps and 24 volt loads up to 80 amps. They are mainly used for 24 volt trolling motors but no reason they would not work on other intermittent loads.