question

Hi @CaptnSnap

Having two separate 'main' banks is your achilles heel. As a mariner you might be pushing for backup, but in this case I wouldn't do it. So forgive me the following suggestions..

Join them into one. At 12V that means 4x parallel batt strings, which I don't like either. So go 24V. 12V loads supplied by an Orion 24>12 converter (or from the gen starter batt which is fed from the Orion).

Get a Multiplus in place of the Phoenix and Centaur. The only downside there is shore V must be the same, but if you ever need 120V ac vs 230V then get a transformer.

The Cerbo a big yes, but you may not need the Touch50. The MFD app might be compatible with that screen on your bridge, and for anything more serious you may have a lappy aboard. The Touch50 sits sorta in-between in capability. The MFD app is getting a rebuild too..

Just one Smartshunt on the main bank, and you could use it's aux function to give a V reading of the starter batt.

The alternator output I won't go into, but that can be dealt with.

Now you mightn't like all this. But I did it (48V even), and I'd never go back..

Hi JohnC and thanks for your assistance. You sound like you know what you are talking about so I am keen to hear more. The boat is actually currently 24V, but because the majority of the devices onboard are 12V, and we have been let down by the 24/12V reducers on multiple occasions, we are moving to all 12V.

The sparky is happy with one connected bank, but the mechanic has absolutely ruled it out. Initially he insisted on a 24V cranking bank for the engines and the two house banks of 12V, but he has come around to 12V engines and therefore 12V cranking banks.

We are in Australia so 120V is just never going to be a thing, and realistically we are only really needing to run a coffee machine with the inverter. There are only two other 240V devices onboard - aircon (never used it in 5 years) and the HWS. Part of the upgrade includes upgrading the HWS to one that has a heat exchanger so even less need for electricity.

The main power use is lights, stereo (two on board plus two amps driving 10 speakers and a subwoofer), and three fridges. I would love to be able to tell you how many amps that is sucking, but the battery monitoring system has been telling us it is drawing 65 amps for 12 months, and we have not been able to work out why.....part of the impetus to upgrade the system.

There is a Glass Cockpit system going in with the engine upgrade, so yes, we will connect that to the Cerbo for full monitoring on the flybridge, but we also want to be able to see whats going on from the saloon where there is no helm. The Touch 50 seems to offer a very simple one-glance synopsis of what all the devices are up to.

I like what you are saying - if we go to one all-in-one house bank and one cranking bank, the Multiplus will handle trickle-charging the cranking bank while she is in the pen, and adequately channel power where it needs to go when she is on anchor.

Back to shunts - if we go with a cranking and a single house-bank, will I need one on both banks? Its so hard to see from the product info what monitoring the Multiplus is capable of.

@CaptnSnap

A shunt on a starter batt is a bit of a luxury. Up to you, but I find Voltage-only enough. (and I have 675Ah/12V of starter batt for my engines, lights, and minor oddities).

A Multiplus (or even a Quattro) has lots of unadvertised options. I use an 'Assistant' within to switch an Orion to charge my starters when the 48V bank reaches a certain V (ie. when solar/genset is charging). And for emergencies I keep aboard an ac to 12V dc charger (40A) I can hook to the Multi. The Orions are rock solid, not Chinee crap, so I've never used it.

I can't help with your mechanic, mine listens to me (err, he is me). :)

Happy to help with anything else where I can, I'm in Oz too, 60 ft liveaboard, and this stuff is my hobby..

The multi plus will give you far better integration with the cerbogx and also take up less space and be lighter than two independent units.

You also get power assist when you are on shore power which is a bit of a killer feature.

If your having additional alternators then, you can easily combine the output from them (you will need a certain model or external reg like a wake speed to get the most out of it) and have a single bank at 12v

Assuming you have the room you can and probobly should retain independent starting banks.

I would stick at 24v personally and then install a buss bar fed by multiple converters for redundancy. You could carry a spare! The weight and cost you will save just in wiring is tangible!

Hi again smart peeps. Just about to push the "purchase" on the following combo so please let me know if I have forgotten anything to consider:

Multiplus 500va-1800va 12V

Cerbo GX

Touch 50

Smartshunt

We already have a Smartsolar MPPT100/50 installed and working a treat.

We are going to combine the previously planned 2 housebanks into one 12V bank, and leave the cranking batteries as 24V for now. Between now and next July when the engines arrive we can decide whether we go to 12V or leave them as 24. We have a portable 24V charger that will keep the 24V bank happy till then.

The smartshunt is for the cranking bank and is probably overkill, but now that we have started this, I really want to be able to monitor all the power flow, including in/out of the cranking bank.

My first question is to check that we dont need a smartshunt on the housebank - I assume the multiplus will tell us everything the smartshunt would and more?

Second question is whether we need additional lead/connections in order to allow the multiplus to switch on the genset, and allow us to monitor black-tank levels? While we wait for the new engines, we will connect the Cerbo to the Raymarine MFD - do we need a special lead for that?

Thanks team

Will it be the Cerbo or the Multi taking input from the 2 shunts, MPPT and Multi, and displaying SOC etc? I assumed the Cerbo was the brains of the network? House bank will stay 12V - craniing bank likely to go from 24V as it is now, to 12V when we get the new engines, so no need to change Multi.

Re alternators and Orions - the engines produce a whopping 150A each at 12V. So can I assume we will be producing 150A per alternator (4)? One set/pair of alternators will be charging the cranking batteries and the other the house bank. Do I need one Orion per alternator or per bank? Do they even make them to handle 150A?