Change from 32 volt to 24 volt (or even 12 volt)

Bertram indeed used 4x8 volt batteries. Definately have a house bank as well, that way you can parrallel the engine bank with the house bank if it's low. I haven't seen the AGM's last any longer really, but as Pascal said, you don't have to add water every month.

On the 54' Bertram, the house bank is up by the generator and I believe shares double duty as house and gen battery.

You also are going to want a 12 volt bank for electronics mostly. Electronics don't like a lot of noise on the batteries they're using either.

You can't use 3x12 volt batteries because that's 36 volts and they won't charge properly or be fully charged with a 32v system.

I haven't seen AGM's go any longer in a cool location either. I see them last about 6 months longer than lead acid. Generally I see 2-3 years on lead acid, and slightly more on agm. HOWEVER, the really good gel batteries I have seen go at least 6+ years on every boat I've managed...The ones that are grey in color......and most push 8+ years. Most of the newer boats are under-batteried for the size engines they have and that's why the batteries just don't last a long long life..... One boat I manage has 2 8D's to start a C32 CAT for example....that bank of 2 batteries is seriously getting wacked everytime that starter turns over.......I see it on numerous boats.

Yeah except your boat has 6-6volt batteries to start a 8v71N, not 2 8D's to turn over a 12 cylinder diesel. In the latter situation you're maxing out the cranking amps of the batteries (almost) everytime you start the engine.

Because it's getting impossible to find new parts for old 32 vdc stuff. Search for a new 32 volt charger, a bilge blower, and various other parts. Try to convert an old galley made head to a modern head. More and more manufacturers are no longer supporting 32 volt stuff. Forget trying to find it while travelling....... What about lightbulbs and various other things. It's simply being phased out. The only Rule pump you can find in 32 volts is a rule 2000, no other sizes. And, if a guy has a Bertram like the OP and has many 32 volt items that aren't working, it's the perfect time to upgrade. I'm dealing with a 54' Bertram right now that has 60 g IV lightbulbs, they stopped making halogen or xenon G IV lightbulbs 2 years ago in 32 volts...... so $30 LED's rated at 10-36 VDC are the only alternative, except you have to change an entire room or the ones you've changed look REALLY different compared to the others.....The cheaper LED's are only rated to 30 volts........Every part is a mission to source now. What about a 32 volt macerator pump.....etc.....etc.....etc.... the list goes on and on.....and it's only going to get harder.......If you're going to change most items, the logical solution would be to upgrade. Even batteries are hard to source in a lot of area's in 8 volt. The Bertram wiring is large enough and should be fine to go to 24 volts, but at that age even in 32 volts, the wiring is at the end of it's years due to the very large bundles Bertram ran and the heat concentrated in the bundle......30 years is a long time for wiring in a yacht.

Pascal's boat origionally would have had 2 6 battery banks of 6 volt batteries all about the size of an 8D. One shared house and stbd engine, the other port engine........ My comment on batteries not lasting is referring to a lot of the newer boats that are running minimally sized battery banks for very large diesels. Especially the newer computer controlled diesels that are also firing off fuel pumps, injectors, computers and etc when they're starting.

I used to run a 32 volt 58 Hatteras Yachtfish that had 2 vaccuuflush toilets that were installed by vaccuuflush, and they both had newmar voltage stepdown converters installed by Vaccuuflush. This was done back in 2003. But, I don't see how any DC motor will last if you are operating it with a much higher voltage.

If you run a 32 volt motor on 24 volts, it will use a lot more amperage and create a lot more heat in the windings and it will not last nearly as long. If you run a 24 volt pump on 32 volts, it will also turn at a rate faster than it was designed for, taxing it's design parameters, and shortening it's life and will also many times cavitate or airlock and not pump because the impellor will be spinning faster than the body and pump housing were designed to pump as well as the passages were designed for. Not to mention none of the parts will be warrantied by any manufacturer. Not to mention if you run a 24 volt sealand waste pump on 32 volts, it will destroy the bellows in it in rapid fashion. A rule 24 volt bilge pump on 32 volts will cavitate and not pump water, then within a few hours of runnning overheats and melts itself or snaps the shaft off (I tried this once).

Using a 24 volt pump on 32 volts, you're talking about a 40-50% increase in power and speed. Operating a 32 volt pump on 24 volts, is a 40% reduction in power and speed. Way outside of the design parameters of anything.

Just like you don't use 3-12volt batteries on a 32 volt system.