3-Phase Multiplus ii Setup – How to Integrate a Generator for Battery Charging?

DIY
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1

Hi everyone,

I’m currently building a 3-phase off-grid/backup system for my own use. Here’s what I have so far:

3x MultiPlus-II 48/5000

1x SmartSolar MPPT 250/100

2x Pylontech US5000 batteries

1x Victron 3-phase Energy Meter

At the moment, my house is connected to the public grid in a standard way, but I’m preparing to switch to a more resilient and flexible setup.

One of my key requirements is to be able to connect a generator to the system for occasional battery charging. I want this to be as plug-and-play as possible – ideally, the generator could just be plugged in when needed, and the system would automatically recognize it and charge the batteries without requiring any manual changes to inverter settings.

What else do I need to achieve this? Are there any specific components or configuration steps I should be aware of?

Thanks in advance for any guidance!

2

In any case, more Batteries for 3x5000 Multis . You are still connected to the mains, but with battery operation your 3x5000 are too much for just 2 Pylontech.

Do you want to go completely OFF GRID or can you return to the grid if you HAVE to?

To avoid the problem of the multis recognising the mains and not recognising the generator, I would always use a separate power supply for 48v … e.g. Eltek or Huawai and then you can also use an AVR generator … preferably a Campion or Könner und Söhne with gas operation. You don’t need anything else for normal charging … for the ‘Generator’ visualisation, a shunt with the ‘DC charger’ setting …

The alternative would be a 3-phase generator with inverter which would then run on all 3 connections of the multis and MUST also be ‘unbalanced load capable’.
A ‘rocking’ AVR generator might be recognised but quickly rejected.

3

Thanks for the feedback!

My plan is to eventually expand the system to 4× Pylontech US5000 batteries.

Under normal conditions, I’d like to use the system in ESS mode – charging the batteries via MPPT during the day and discharging at night to cover household loads (a typical energy storage setup).

However, in emergency situations (e.g. grid outage), I want the installation to seamlessly switch to off-grid operation, running off battery power and optionally charging via generator.

Could you please suggest specific DC charger models that would work well for this use case?
I’m looking for something robust and compatible with the Victron setup – ideally with decent monitoring options and as little manual configuration as possible.

Thanks again for your help!

4

In any case, you need a generator that

  1. has enough power to supply the necessary charging current … e.g. 6000kw charging power
  2. the fuel supply lasts long enough without going ‘bad’. Petrol and diesel are out of the question for me.
    Therefore a Champion bifuel generator for petrol AND camping gas.

I use ELTEK chargers, which can also be extended as required …
The important thing is the voltage setting … I charge with 51.5V … that’s easily enough for 90% SOC

Meanwell or Huawai are also possible

Important for all chargers is the very wide input voltage range in case your alternator oscillates. They simply keep charging.

And you can also use the 230V for something else while your battery is charging …

5

Well, I’d take a Hyundai Diesel, use fuel-oil for heating, cheap, easy to transport, low risk level.

As charger I’d probably take an old 3-phase transformer based one from a forklift-truck, oldschool, no fuss, no nonsense.

Excess power can always be used for heating water for pool or showers.

And, never forget, these emergency units MUST run at least once per month for 1 hour under load.

6

How would you charge lithium batteries? Through the victrons ?
I would like charging the batteries on DC side but here come the problems?
Using a SmartSolar 250-100 for directly charging the batteries and controlled by the Cerbo would be my preferred option..