We live on a barge and left the city again for the “summer”. Because the PV doesn’t do enough yet, we use our 4k generator (as we do for years allready) to top off our BYD-set daily.
This time after switching from ESS (in the city) to offgrid, the MultiPlus II only charges with around 40A. The CCL of the BYD, with this temperature, says to be 140A, so I’d expect the MultiPlus to charge at the max, but it doesn’t. The Multicontrol is set to 19A and when doing a laundry at the same time, the MultiPlus II takes more power from the generator (up to the 4k). So I guess the generator is not the limiting factor here…
Does anyone have any suggestions?
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Do you have “weak ac” on ?
Absolutely 
Well, weak ac throttles the charger…
In what way does it throttle it? The years before this one, the same generator got the MultiPlus II to charge up to the capacity of the generator…
I don’t know if it’s deliberate or a side effect, but WeakAC applies a poor Power Factor to the incoming AC and the charge circuitry doesn’t like it. Indeed the effect is quite severe and you’ll never get near the rated 70A, 40A typical.
Nor is this anything new, it was there before the Multi II model.
You’ll need to disable it, and if your gen can’t handle that then you should try to find out why.
When I disable weakAC, the Multi tries to “sync” it’s sinus to the gen (I think?), instead of just gobbling up anything it gets Or is that the “UPS-setting”?
As it is not a high end gen, it will not find “common ground”, not sync… and thus not charge at all 
I can see in the dashboard, that the power provided is not very much “out of bounds”, as the AC-out (which comes from the gen) displays around 218V and around 49.8Hz. Both reasonably steady, as far as I can see.
Weird is, that the years before this one, the charger of the Multi did charge up to the max, the gen could provide, and now it gets stuck at around 40A…
So I hoped that maybe there’s something I forgot to set in VEConfig the right way, blocking the charger to pull as much power from the generator as it can provide…
What version do you have in the multiplus ?
At the moment 2623508. I updated sometime last year.
Ok, 552 might work better in generator mode.
You should upgrade and try again.
Thanks. I’ll try
The gen may be gagging on the instant 70A hit, plus the loads. It may then go offspec and get rejected. All happens fast.
Try enabling ‘Dynamic Current Limiter’ in VEConfig. It’s like a soft-start, to give the gen a chance to wind up over a few seconds.
That 218V you may be able to adjust with a throttle tweak.
General stuff… MultiPlus Generator FAQ [Victron Energy]
Thanks. I’ll keep that in mind. Although my experience, from the past years is that the gen I use throttles up quite fast, up to the max amps I set in the Multicontrol (19A). It’s a construction-site gen, which is used to “misusage” The avarage loads are not very high (around 200W).
The 218V, I’m not completely sure of the source of that reading…The gen says it delivers around 230V, and I can’t imagine losing much voltage in the used cable…
As far as I remember, last year almost all that voltage arrived at the MultiPlus…
I’ll put a multimeter directly at the gen and look how exact the voltage is that the multimeter reports at the gen, compared to it’s own measurements
By the way… I checked the changelog for the firmwareversions since 508 and don’t really see something gen-related having changed. But maybe it’s somewhere in the changes that ALSO has a positive effect in gen-operations …
Haven’t tried the update yet. Planning to do it tomorrow.
Check 509 “bugfix”
Updated yesterday to firmware 555 and now everything behaves as expected again. The MultiPlus II gobbles up everything it gets thrown at it again 
Thanks for the tips!