question

https://www.victronenergy.com/live/multiplus_faq

An SDMO in the 6 to 10 Kva range would be a nice choice

LG Resu are not a good choice for off grid set-ups however. 2 x BYD B-Box or B-Box pro would be better, or Victron home brand Li Fe PO4

batteries already exist- we have an existing system where the inverter is not coping, so I need to swap it out.

that multiplus page is what I was referring to- it says AVR units are ok. I guess I just want to validate that people find they do work ok and that I don't need an inverter unit.

Hi Bryn. I don't think Victron have any particular recommended types (at least officially), and they've put some work into testing them (perhaps before the inverter era). This is ageing a little now, and it's quite lengthy, but you may have your eyes widened if you delve to the more technical aspects: https://www.victronenergy.com/upload/documents/VE_Marine_generator_test_RVA_07-jan-2008.pdf

I've a 48/5000 Multi at home and have used both types. The Multi is fairly picky about power quality and my old Yamaha AVR it doesn't like. But can be tweaked to accept it, with some loss of power capacity and efficiency.

If you could find a supplier to 'guarantee' acceptance by the Multi, then go for it.

I use a Cummins Onan 4.8 me, it works really well, and it's easy to integrate the remote start

I run a Kubota 1105BG close coupled to a Mecc Alte (manual switching 1ph/3ph) 230/415Vac Alternator . AVR is digital, rock solid. Power quality is very good. 49-52Hz, 6kVA cont, 9kVA int', runs at 3.3 kW for 3hrs / day now that I have upgraded to Lithium. 2x Multiplus 3000's(parallel) set for 32A input current limit. Murphy Auto-Start. Engine coolant is fed through heat exchanger and provides ALL of my DHW + some house radiators. Its all over 15 years old now, just regularly serviced replaced the water pump once.

Get something with a high quality Digital AVR, I've set up multiple now with Westinghouse AVR units and at all of the sites the multiplus accepted power with UPS enabled.
I've also seen kubota lowboy GL9000's work with UPS ticked.

I've seen cheap sabre generators need UPS switched off, as well as a couple of 1500rpm kubota's (these were rebuilt units so god only knows what the Alternator was)

The westinghouses with the wave flow muffler are quiet for what they are.

Bottom line, don't go cheapest. Fuel type is going to be a deciding factor.

For a 5kva multi, you want something in the 6.5kva continuous output.

Don't get an inverter unit, sure they can work with current limit, but after running at close to its rated load for for a few hours the inverter in the unit will overheat but the engine will keep going and you won't know if you don't hear the rev change.

Does anyone have any suggestions for a 10 - 14kVA diesel generator that works well without "Weak AC" selected?

I use on of these, Hyundai 18kW/22.5kVA Single Phase Diesel Generator | DHY18KSEm (hyundaipowerequipment.co.uk) a bit bigger than you asked but there are smaller options... Hyundai 9kW/11.25kVA Single Phase Diesel Generator | DHY9KSEm (hyundaipowerequipment.co.uk)