Thinking of going 24 volt with the new boat

[GILow]

So, the decision was made to go all electric with the galley on the new boat. This in turn led to a decision to go with a lithium battery bank (despite being VERY happy with my faithful old Trojan T105 bank in the old boat.)

Now I’m thinking, should I go 24 volt too?

On paper it makes good sense and certainly makes the electric galley much simpler. The battery configuration was going to be 4 x 100 AH 12v lithium batteries, so no problem there.

However, I have a some legacy gear that is 12 volt only and I’m keen to hear how people choose to power this stuff.

Aside from the windlass, which I think can either be rewound or perhaps repowered with a new motor, I have an Icom M802 HF radio, some decent audio amplifiers, an autopilot motor and a smattering of smaller stuff.

The Icom wants about 30 amps, the amplifiers are about the same. The autopilot peak load is about 10 amps, the smaller stuff mostly around five amps.

Oh, yeah, the fridge is 12 volt, about 8 amps peak load and gets through at least 40AH a day.

I wondered about small dc to dc power supply providing a 12 volt bus? Or maybe a dc to dc charger supplying a small lithium or LA battery?

What are others doing?

Matt

[rslifkin]

The fridge might be 12/24 volt. Many of the Danfoss compressor units are. You just might have to change a light or something.

Personally, I'd probably go 24v. Add a small 12v bank (a single group 31 or something would do) and an appropriate size DC-DC converter (or several). The 12v battery stays in float all the time unless something fails. It just acts as a buffer. In theory you could use just the converter without the battery as well if the converters handle sudden load changes well enough.

[Jim Cate]

If you go for the DC-DC for the Icom, be sure that it is not RF noisy... some of them are great RFI generators. And while peak loads can approach 30 A @ 12 nominal, even running full power those loads are transient and short lived, and if you run it at reduced power, even the peaks are lowered. IME, it is not common to need more that ~30-50 watts to be quite successful in HF comms.

Jim

[GILow]

Originally Posted by rslifkin

The fridge might be 12/24 volt. Many of the Danfoss compressor units are. You just might have to change a light or something.

Personally, I'd probably go 24v. Add a small 12v bank (a single group 31 or something would do) and an appropriate size DC-DC converter (or several). The 12v battery stays in float all the time unless something fails. It just acts as a buffer. In theory you could use just the converter without the battery as well if the converters handle sudden load changes well enough.

I’ll double check the fridge, it’s an Ozefridge and I think they use their own compressors or something odd.

But one vote for the extra battery noted.

[GILow]

Originally Posted by Jim Cate

If you go for the DC-DC for the Icom, be sure that it is not RF noisy... some of them are great RFI generators. And while peak loads can approach 30 A @ 12 nominal, even running full power those loads are transient and short lived, and if you run it at reduced power, even the peaks are lowered. IME, it is not common to need more that ~30-50 watts to be quite successful in HF comms.

Jim

Good points Jim. And even a DC to DC smart charger may be noisey too.

[Ballsnall]

Originally Posted by GILow

Now I’m thinking, should I go 24 volt too?

On paper it makes good sense and certainly makes the electric galley much simpler.

So you have 3 options,
1. Go 24v and convert or replace all 12v equipment
2. Go dual 12v / 24v systems
3. Stay with 12v

From what you posted it seems the gallery stove is the only non 12v equipment you have so I don't know how going 24v will be simpler? Assuming your stove will be AC, it's only a minor efficiency loss between a 12 & 24 volt inverter. To me, it seems changing from 12 to 24 will be more expensive and going dual system will be more expensive and more complicated.

If you do go dual system then a LA float battery would be what I would recommend, maybe even repurpose a couple of your Trojans.

[GILow]

Originally Posted by Ballsnall

So you have 3 options,

1. Go 24v and convert or replace all 12v equipment

2. Go dual 12v / 24v systems

3. Stay with 12v



From what you posted it seems the gallery stove is the only non 12v equipment you have so I don't know how going 24v will be simpler? Assuming your stove will be AC, it's only a minor efficiency loss between a 12 & 24 volt inverter. To me, it seems changing from 12 to 24 will be more expensive and going dual system will be more expensive and more complicated.



If you do go dual system then a LA float battery would be what I would recommend, maybe even repurpose a couple of your Trojans.

Going to 24 volts has some big advantages. For a start you can get much bigger inverters, which matters with an electric galley. Either I get multiple inverters (3 or maybe 4) or I have to take care that I don’t use the coffee machine while the stove is on, etc etc.

Also, wiring 24 volts is cheaper and easier. Halve the cable thicknesses on the big stuff.

Solar regulator costs halve by going with 24 volts, a BIG item when you are looking at 1500 watts of solar.

I have plenty of stuff ready to install which can run on 12 or 24 volts. I already have the plotter, instruments, radios that are dual voltage.

So there are plenty of incentives, financial and practical, to go dual voltage. Just working out what solutions people have used and see how they stack up.

[s/v Jedi]

Can you tell me

- what kind of boat did you buy? Length?
- what batteries were on board? Start bank?
- what appliances do you want in the galley?
- what shore power do you want?
- do you want a generator, solar, windgen?

[RaymondR]

Definately loke the idea of going 24 volt on the house system.

I'd be inclined to retain a gas stove and install a good microwave.

Since we're most likely to build 24 volt systems from either cells or 12 volt batteries we need some of the younger members to dream up a system that allows us to cycle between 12 volt taps in the 24 volt system so the 12 volt sections stay in balance and avoid the voltage converters.

[GILow]

Originally Posted by s/v Jedi

Can you tell me



- what kind of boat did you buy? Length?

- what batteries were on board? Start bank?

- what appliances do you want in the galley?

- what shore power do you want?

- do you want a generator, solar, windgen?

Kelly Peterson 44, bare hull. No electrics, not one single wire. I kid you not. No batteries. Nothing. A perfect clean slate.

Thinking three “burner” induction cooktop and an inverter convection microwave for the galley.

Shore power negligible, I’ve lived without it for years now. Of course I have a little Victron smart charger, 10 amps I think, for maintenance, but solar does all the heavy lifting.

The boat will be practically pure solar. No wind gen, and only minor engine charging. I should be able to fit 1.2 - 1.5kW of solar.

To elaborate my assumptions, I’ve survived very easily on 760 Watts of solar for five years now, but with a gas cooktop and 675AH@12V of Trojan T105s. That’s with a nasty espresso coffee machine habit from 30 years in IT, plus a microwave oven. From what I’ve read I need to add one more kilowatt hour per day for the cooking if I switch to an induction cooktop. (This number correlated perfectly with the two months I get from a 4.5kg lpg (propane to northern hemisphere guys) gas bottle.)

So I THINK I’ll be fine with 400AH@12V (or 200AH@24v, yeah, I know, I should just use kWh) of good quality lithium (with maybe a home brew BMS, I’ve heard there’s some guy here who shared his design )

Separate engine battery. A DC to DC charger from engine to house bank for emergencies.

Thoughts?

[GILow]

Originally Posted by RaymondR

Definately loke the idea of going 24 volt on the house system.

I'd be inclined to retain a gas stove and install a good microwave.

….

This was the original plan as a matter of fact. But I’m a stress head about gas and I realised eliminating it from the inside of the boat was both feasible and attractive to my personality disorder.

I will still maintain my beautiful Weber BabyQ on the aft rail with a small gas bottle, but that does not require me to run gas pipes into the boat. It will serve as a cooking backup if I have an inverter failure.

[coopec43]

Hi Matt

I have a dual system. I use a DC-DC Converter to power 12V lights, fans, charging outlets (for phone, torches etc), radio, search light, depth sounder, computer.

When I checked (by brand) I found the engine instrumentation (oil pressure, tachometer, water temp) will run on 12V or 24V

[GILow]

Originally Posted by coopec43

Hi Matt

I have a dual system. I use a DC-DC Converter to power 12V lights, fans, charging outlets (for phone, torches etc), radio, search light, depth sounder, computer.
…

So, what current does the dc to dc converter support?

[Audeamus]

When we installed lithium we changed from 12 to 24v. Driven by cable size saving & inverter size as we went electric cooking The anchor windlass hydraulic winch motor & bilge pumps we converted to 24v - bow thruster was already 24. All other items on the boat we kept 12v. Instrumentation, auto pilot, refrigeration, entertainment water pumps etc. Victron 70amp DC DC converter with no buffer battery. Been good for 18 months so far.

[GILow]

Originally Posted by Audeamus

When we installed lithium we changed from 12 to 24v. Driven by cable size saving & inverter size as we went electric cooking The anchor windlass hydraulic winch motor & bilge pumps we converted to 24v - bow thruster was already 24. All other items on the boat we kept 12v. Instrumentation, auto pilot, refrigeration, entertainment water pumps etc. Victron 70amp DC DC converter with no buffer battery. Been good for 18 months so far.

Great data points, thank you, and we do love our Victron gear too. I’ll have a look at that converter.

How much of the 70 amp capacity do you think you’ve needed so far? Or, in other words, how would you go smaller or larger if you did it again?