Quattro & Pylontech erratic charge current on Generator

Hello,

We are off grid system installers, having fitted a number of Victron systems on-grid, off-grid with and without generators. In this case, we have an off-grid system installed on a farm, compromising of the following;

3 phase setup with 2x 48/15000 Quattro per phase ( 6 units total )
2x MPPT 450/200
2x Fronius Eco 25kW
24x Pylontech US5000
Cerbo GX

System works flawlessly, charging / discharging, even under loads of 40kW. Until the generator starts. While the generator is running, the charge current fluctuates ( reading from Cerbo screen on Quattro page ) by around 100a constantly. This causes the generator to run poorly and it often cuts out or causes fluctuation of the voltage on AC Output.

All systems are up to date, every setting has been checked and compared to the other systems we have installed working correctly and there seems to be no obvious reason why the charge current should fluctuate the way it does. We have also tried turning the Pylontech BMS control off, DVCC settings all off just to see, but it continues to fluctuate the charge current.

Does anyone have any other ideas on what may be causing this fluctuation?

What size is the generator?
Sounds unstable at the load that is on it.

What assistant do you have controlling the fronius?

Thanks for the reply.

It’s a 200kVA generator, reasonably new and well serviced. If I drop the charge current down to less than 10a through DVCC the generator will run fine, covering loads no problem.

Fronius are controlled with frequency shift, set up with PV assistant. All settings triple checked.

Even if the fronius is off it will still fluctuate, we just can’t understand it!

How high is the frequency of the generator when you are under 10A charging current?
And what is the frequency curve if you do not set it … does it fluctuate a lot depending on the load?

The load doesn’t seem to affect it, it’s just the charge current.

When it’s bad it’s fluctuates between 49 and 52, quite rapidly.

When it’s ok, it’s stable around 50.5

In which SOC area of the pylon techs does this happen? Always ? or have you looked at the charging parameters of the Pylontech … CCL , CVL ?
What charging voltage do you use via the ‘charger’ setting of the Quattros …
Input 2 used for the generator ?

It seems at any SOC it does it but I would say worse above 60%.

Absorption 52v float 51.5v

Generator on input 1, nothing on input 2

Never reaches the CCL or CVL, they remain stable.

It’s just the quattro it seems that just cannot control the charge current for some reason