Inverter Upgrade - Victron MultiPlus [circuit diagram]

David Vogel

Hi Chris,

Attached the block diagram for Multiplus install.

I'm still in the process of finalising the electrical line diagram following the rewire of the NAV STN and N2K network - because the design has been quite dynamic as I've learnt stuff along the way, and the concept/s evolved, I've found it better to do it by hand (quicker and easier for me to revise than doing it on the computer) - so, still with many incremental changes drawn on, it's barely readable. As soon as I have something half-way decent, I'll post it to the forum.


SM#396, Perigee

From: <> on behalf of "Chris Paul via" <chris__paul@...>
Reply to: <>
Date: Saturday, 10 December 2022 at 10:11 am
To: "" <>
Subject: Re: [AmelYachtOwners] Inverter Upgrade - Victron MultiPlus

Hi David,
Impressive. Having read it all & trying to understand - my brain hurts!
I would be very interested in a circuit diagram, if you have one you could share.

I am about to install new navigation instruments with upgrade to N2K. 
I'm thinking about the 12V side. 
The existing 24-12 converters appear to be very robust but complex wiring.

I'm wondering if it is worth installing an isolated Victron 24-12 converter.
The 12V wiring behind the chart table could be simplified into a single bus bar & bluetooth monitored.
I am keen to hear from anyone who has done this.

Regards, Chris Paul 
Whangarei, NZ

On Friday, 9 December 2022 at 02:23:31 pm NZDT, David Vogel <david.vogel@...> wrote:

Hi All,

My inverter upgrade, augmenting the pre-existing 1,500W inverter (as installed as OEM) with a Victron MultiPlus (24/3000/70-50), is finally complete.

Below, documenting the generic system configuration and underling rationale/s, for the benefit of those facing similar upgrades in future.

The planning started shortly before acquiring Perigee in 2016, with the initial PV (4x 100W, rail-mounted) installed in MQ 2017; then WindGen in SXM, 2018 (Rutland 1200, top of mizzen mast, made easier when the masts were removed for replacing the standing rigging with ACMO to OEM spec); M2-1828 AC multi-meter ordered / delivered Panama, 2018 (faulty on delivery, replaced 2022 under warrantee).  Victron Multiplus ordered when the legacy AGMs started to fail in French Polynesia, late in 2018.  The Multiplus arrived NukuHiva, along with 10x Firefly batteries, in February 2019 . The batteries were installed immediately, but the Multiplus install has needed to wait for a more integrated systems approach (and an AMEL-friendly electrician), and to await a location with readier access to a suitable level of shore-based resources and support; detailed discussions with 4 installers took place along the way, before finally settling on a fifth, who assisted with the job, along with cleaning up the rats-nest of the DC wiring adjacent to the battery box (e.g. new +ve and -ve bus-bars, adjacent to the battery switches, and other aspects of prior solar and wind-gen installs).

Points-of-interest are:

Battery Monitoring: replaced the Xantrex Lite with a Victron BMV-712, which is networked via Bluetooth and VE-Direct; this works in combination with a Bluetooth networked Victron SmartSense which provides networked temperature sensing (and battery voltage sensing, as used by PV MPPTs).

Victron MultiPlus 24/3000/70-50.  Chose VICTRON over Mastervolt - as did not see the need for cZone integration, as (perhaps, and arguably) this is the primary benefit of MV over VE; have a tendency towards the potential of open-source solutions as well.  Then, chose the Multiplus over Quattro, as have taken an in-principle decision that "if it ain't broke, don't fix it", that is, to re-use as much as possible (in this case, the existing K1 / K2 transfer switches, and associated wiring & cable runs), whilst also minimising disruption to other existing/working equipment and systems.  Adding 3,000W of inverting represented a doubling of the pre-existing 1,500W inverter (which has been retained, using the pre-existing K2 transfer switch, so as much as possible remaining independent of the Multiplus install).  Also, chose a 3,000W (not 5,000W) unit, as a greater-capacity inverter would need higher-capacity batteries which, in turn, would need to be kept fed with higher capacity charge-source/s (solar).  Similar rationale for 70A charger, not higher.  Also, adopting an evolutionary approach, such that incremental improvements (such as increase in inverting capacity) does not drive or necessitate an upgrade elsewhere (such as Lithium).  Holding to 3,000W will also (I hope) limit the consequence of the "use whatever you have" effect.  Chose the unit with 50A transfer rating, over the one with only 16A capacity, so as to be able to passthrough the full output of the 7.5kVA ONAN GenSet (for battery charging, amongst other things).

Multiplus, installed in hanging locker adjacent to companionway.  Rationale:
1. minimise length of DC cable runs;
2. avoid the heat of the engine room - having experienced heat-soak in the engine room, did not want add more heat sources there;
3. avoid having the Multiplus co-located with the other inverter and chargers (i.e. physically separate these pieces of equipment, if possible, to guard against broad-scale effects of an engine-room incident such as water-maker HP leak); and
4. reduce risk of heat-related reduction of inverter/charger efficiency due to high ambient temperatures.
Downside: extra noise in saloon when with high charge/inverting loads.
Offset: co-locate with new solar MPPTs, clear access to associated RCDs, CBs, distribution/fuse boxes, etc.

System configuration: via VictronCONFIGURE (for initial setup), thereafter VictronCONNECT (app on iPhone, iPad; and MacOSX via USB-C into ethernet/VE-Bus) and VRM (browser via internet, plus local).

Monitoring - Multiplus (and system): via Victron CERBO GX.  Elected for the CERBO over an OCTO GX, for the more powerful CPU and better WiFi performance (despite the 10 VE.Direct ports offered by the OCTO; CERBO has only 3); use VRM app on iPhone/iPad and online, and B&G MFD at NAV STN (details below).

Control - Multiplus: Digital Multi-Control panel (DMC-GX), located below the ONAN control panel in the galley.  Rationale: try and keep all the primary charging and inverting controls located within a single eye-glance and arms-reach.  (The legacy 1,500W inverter has been held in situ, and still able to feed the AC system via K2 when the Multiplus is off.)

Monitoring & Control - Cerbo & System: via VRM (browser, and app) and HTML5, the latter achieved via ethernet to a B&G Vulcan 7" (V7) display.  Elected to go this path in order to avoid the need for a separate dedicated display for the Cerbo (power, space & visual considerations); achieved by using the pre-existing B&G Vulcan 7" MFD, which has been panel-mounted (with only minor work required) to replace the retired B&G Hydra2000 display.  The V7 also provides back-up/redundancy to the Furuno TZT14 chartplotter and integrated AIS functions at the NAV STN (but the V7 does not provide redundancy for the radar), while also providing enhanced wind information (waterfall history tapes) as per helm instruments (3x Triton2) - this is very useful when in inclement conditions, as can assess all parameters from below, at the NAV Station (note: all autopilot controls have been deliberately retained at the helm only).  The CERBO is also connected to the N2K network (note: the CERBO's 12vDC N2K-supply fuse is removed, in order to avoid DC loops), meaning that electrical-system status and values (such as AC/DC voltages, currents, temps, warning & alarms, etc) can also be displayed on dedicated windows on the V7 MFD (and anywhere else where the N2K data-stream is available).

Other changes:
+ installed Victron battery balancers.

+ N2K network is newly separated into two independently-powered halves: <MHU-to-DST-to-NAV STN+xxx> and <Chartplotter-to-Autopilot-to-helm-to-GPS330B>.  (All N2K data that is available on one half, is passthrough to the other half.)

+ Furuno TZT14 Chart-plotter (and radar, plus the primary FA-50 AIS) 24V supply is powered by the main NAV STN circuit breaker via dedicated sub-bus; the 12VDC supply to the chartplotter, which powers the 'aft end' of the N2K network, is powered by the NAV STN SAILOR 8A 24-12VDC supply.

+ re-allocated previously unused capacity on the Sailor 8AMP "Always ON" 24-12VDC converter (previously FM-AM radio only, channel pre-set), now provides "Always ON" (but switched) 12VDC to the 'masthead half' of the N2K backbone; this power supply now also powers the CERBO, the B&G V7 MFD (which is also separately switched), and a (switched) 4G/WiFi Router.  Doing so allows the CERBO to be monitored and controlled remotely (unless the Sailor 'Always ON' 24-12v DC-DC converter is switched off at the unit).

+ reconfiguration of the AC panel so that the pre-existing 100A and 30A battery chargers are powered only from the Multiplus AC-OUT-2 (AC-OUT-2 is switched only when AC-IN is available to the Multiplus, from either shore-power or genset, genset priority, as determined by AMEL OEM transfer switch K1).  Thereby preventing an inadvertent charge-from-inverter downwards-spiral scenario, whilst also providing boosted battery charging capacity of up to 100+30+70 Amps (or combination thereof, max. 4,800W from 7.5kVA genset; lesser when on shore power, with power limiting applied via DMC panel).

+ Replacement of the analogue AC voltmeter (above the AC panel) with a Bluesea M2-1838 AC Multimeter; enabling greater visibility of AC loads at the point-of-control.

+ Installed VESPER XB-8000 (in SW controlled RX-only mode): provides on-board MOB and Anchor Alarm, plus AIS to helm instruments (3x Triton2) and V7 via N2K.  Re-broadcasts the AIS and N2K data-streams via WiFi for use by independent devices (e.g. iPads/iPhones running iSailor, PC/MAC running O-CPN).  Provides redundancy for the primary Tx/Rx AIS (which is an ethernetworked Furuno FA-50 displayed on the primary TZT14 chartplotter).  (I elected not to go for the integrated CORTEX solution, as I wish to retain AIS independent of VHF COMs capability.)


Replacement of 4x 100W rail-mounted solar panels with 4x 310W panels (2 on the rail, one each port and starboard; 2 on bimini).  Replacement of 1 x 100/20 MPPT with 2x 100/30 MPPTs; retaining the 100/20 thereby providing the optional election of retaining some of the existing 400W, or supplementing the new 1,200W with fore-deck or boom-tent mounted flexible / semi-flexible panels.

Future considerations:
Upgrade to Lithium: contingent upon aging capacity of existing 580Ah FireFly batteries, assumed timeframe remaining 3-5 years, at which time the presuemed costs of lithium with reduce in real-terms, as well as leveraging the benefits of flow-on technologies resulting from EV uptake, hybrid grid-storage solutions, systemic design considerations in marine applications, modularisation, interoperability, and institutional aspects (e.g., insurance), etc etc.

As usual, comments, questions, and suggestions all welcome.

Blue skies,

  SM#396, Perigee
    Bay of Islands, NZ

From: <> on behalf of Bill Kinney <mailto:cruisingconsulting@...>
Reply to: <>
Date: Tuesday, 12 April 2022 at 12:03 pm
To: <>
Subject: Re: [AmelYachtOwners] Standalone Inverter as an AC IN source to a Victron MultiPlus


Thanks for the diagram... What you propose looks good!

Bill Kinney
SM160, Harmonie
Ragged Island, Bahamas

Dean Gillies

Hi David,
A picture tells a thousand words :)
I was looking at your circuit diagram and have a couple of observations to share regarding your "After" configuration.

1. I note you have connected AC-OUT-2 to your 220(230)V panel via a 32A RCD.   The Victron manual states that the maximum output of AC-OUT-2 is 16A and that it should be protected by a 16A breaker.  This is the problem I've been discussing in your other thread. AC-OUT-2 will barely support the 100A charger at full load and definitely won't support both chargers at full load. You may be able to scrape through with lead-based batteries as long as they don't get so a very low SOC because their low charge acceptance will limit the current. However, if they get sufficiently discharged then you will need to be very careful. Also if you upgrade to LFP in the future, you will overload the Multiplus AC-Out-2 if you turn on both chargers. Given that the Victron product manual states that an external 16A breaker is mandatory for AC-OUT-2, I suspect that the Multiplus may not handle that overload situation gracefully!         

2. You have placed a Class T fuse between the DC bus and the Multiplus. A Class T is not a "Fast-Acting" fuse in the way you might imagine.  In fact it can be very slow-acting in over-current situations.  The main benefit of a Class T fuse lies in its ability to safely disconnect (without arcing) in the presence of very large currents.  Class T fuses are often specified in LFP battery systems due to the possibility of very high short-circuit currents which might otherwise cause lesser fuses to "weld closed" and therefore fail to interrupt the current flow. A Class T fuse should be placed as close as possible to the batteries, whereas it looks like you are protecting the inverter wiring only. Do you need a Class T fuse with your Firefly batteries and will a lesser fuse suffice to protect the wiring feed to the inverter? Maybe one fuse, appropriately placed, will do the job?

3.  I don't disagree with your wire gauge calculations for the AC wiring, but it may be worth noting that AMEL used 4mm2 wiring for the 16/32A wiring and 10mm2 for the 50A wiring. Part of the reason may have been that they were allowing for 115V supply without having to change wiring.  The 10mm2 AC cable is a pain to work with! 

4. Do you have any breaker protection on the 16A shore power feed (pre K1), either existing or planned?  Or just rely on the dock breakers?

5. Regarding cable/breaker sizing at the AC-OUT-1 Multiplus output. Are you aware that the MP can provide up to 63A on that output?  The Multiplus "assists" the output by adding an additional 3kVA (taken from the batteries). This is important when calculating circuit protection parameters. 

Dean Gillies
SV Stella *****,  Amel 54-154