DC to DC converter to carry 12v load?

[nofacey]

After installing 2x6v batteries for 12v starting service, and 8x6v as a 24v bank -and starting to run put of room! - I'm rethinking the need for yet another pair to serve as a 12v house bank.
We were planning to use a 24v to 12v DC converter Orion DC / DC Converters - Victron Energy to support the 12v bank.......now I'm thinking of forgoing the 12v bank, and just running the 12 v load directly off the 24v bank via the converter.

It's not quite so crazy when you take the time to figure out the loads.....all our Garmin nav system - radar, sonar, chart plotter and autopilot - can run off 24v. We need 12v to run the NEMA 2000 network, the VHF, the small main sump bilge pump and the SSB - with the SSB during transmission being the highest (30a) draw by far.

So.......what's the downside of running the 12v loads off a 40a DC to DC converter?

[transmitterdan]

I don't see much down side to this solution. If the DC-DC converter fails then in an emergency you can connect the 12V items to the mid-point of the 24V bank. This would be bad as a permanent solution but in an emergency it will work.

[Stumble]

Expense at around $850 for a converter that can run motors and solonoids.
Inefficient, at around 10% loss

For the type of light loads the efficiency may not be enough of an issue to worry about, and if you could find a 24v SSB the unit price would drop steeply.

Just don't get fooled by the cheap units. They are not rated to handle motors or constant demand appliances. Even lights can stress them. The upside is all your current 12v wiring is already at least large enough, and many 12v things can be replaced easily in 24v.

[senormechanico]

The converter will probably generate some RFI which will mess up reception on the SSB.

[nofacey]

As we were setting up the dingy with an electric start outboard (for the wife, of course), I realized that I want to carry a spare 12v battery for that - and looking at the range of motorcycle/atv batteries out there, I'm thinking that I'll go with either an AGM or perhaps even a lithium, and keep the spare in line with the output from the DC to DC converter - keeping it both charged, and acting as a buffer.

the lithium batteries are amazingly small and light for their capacity.

[Colin A]

The Victron converters work well. We have also had good luck with the Newmars. Plenty of commercial boats are setup with converters to run 12V loads. We have done a few where they have either a manual or automatic change over from the converter to a small battery for emergency power on VHF radios etc.