A client's install has two 48V, 5kVA Multi ii paralleled: up to date matching firmware, identical AC and DC cabling, CCGX, gel battery & suitable solar input. The client has an isolated, completely independent back-up system (via AC transfer switch) incl. its own solar and battery.
With the occasional need for diesel gen back-up (we're in a sunny part of Spain), the client switches the transfer switch to power the loads from the back-up system (cleaner signal to the loads & maximum input into the batt). Then when the batt is full, they switch back to run the house from the Multi system.
The system has worked fine for a few months, and then (following a generator service) last week, when charging through the Multis, the generator stalls almost every time, almost immediately before it's got up to steam.
The gen is fully tested, and works fine powering loads or when charging the separate back-up system.
I've tried swapping master and slave allocation, and this seems to have helped, but as I can't say that this has 100% fixed the issue, the client is understandably twitchy.
If the gen is also powering the loads through the Multis, the gen stalls less often, but still does. This makes me wonder if there's some backfeed issue, explaining why it's much more common when only charging the batt rather than also having a load to supply.
Any thoughts/ experiences appreciated!