12V bank + 24V bank?

[andreas.mehlin]

At the moment 12V system in my boat. Have watermaker for 24V.

Am buying new batteries and solar panels at the moment and not sure if gonna run the watermaker thru at step up converter, or from a new small 24V bank.

Will also buy a new electric toilet and found one in stock for a good price (24V).

This is my options:
A) 525Ah batteries + 12-24V step up converter. All Solar panels to MPPT
pros: ONE big bank. Cons: a converter to fail


B) 420 Ah battery bank 12V, 105Ah 24V bank.Solar panels with a switch which bank to charge.
pros: no converter: cons: another battery bank

opinions?

[Florida Mike]

You might consider converting the boat to 24 V, and running a 24 V to 12v converter. They are quite comen in the heavy equipment industry.
Or run two systems if you can mount a second alternator.
Or solit your 12 V system in to two banks and put a heavy duty double pole double throw switch between them set up to be series parallel. It sounds a little complicated but it’s not too bad in reality. Though it is mostly done for heavy draw equipment such as bow thrusters and anchor winless. If you do this you might consider hooking your solar panels to the high side batteries. Just my two cents, Mike.

[Lake-Effect]

How much current at 24v does the watermaker consume? Does it take both 12 and 24v in? Make and model, if we need to look it up? Ditto for the toilet.

My initial thought is that it doesn't make much sense to have a 24v boat system if only two devices require 24v.

[Pblais]

The main appeal for 24 volt systems is that on much larger boats the length of the runs requires some really thick wires. At some point the extra wire starts to cost more with 12 volt. It's mostly about the money. The design of the overall system is more important. I wouldn't just pick at small parts and details to make this decision. You always pay a penalty converting voltages so don't do it multiple times.

[atoll]

Originally Posted by Pblais

The main appeal for 24 volt systems is that on much larger boats the length of the runs requires some really thick wires. At some point the extra wire starts to cost more with 12 volt. It's mostly about the money. The design of the overall system is more important. I wouldn't just pick at small parts and details to make this decision. You always pay a penalty converting voltages so don't do it multiple times.

+1

[Dockhead]

24 volts is better, but talking about converting your boat just to accommodate one 24v water maker is a major case of the tail wagging the dog. Sell it and buy a 12v one - simples.

[Andina Marie]

Do some research. Starting current on a watermaker or toilet can be quite severe, (up to 10 times running current). You may have trouble finding a 12 to 24 volt DC-DC converter that can handle the load (that you can afford).