MPPT export is low after Dyness LFP Battery is at 100%

Q&A and troubleshooting
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1

Hello everyone,

I have an issue with a new multi-phase system installed. It consists of :

  • 3 x Multiplus II 48/8000

  • MPPT 250/100 tied to 12 x solar panels (6kw)

  • Cerbo GX

  • Dyness PowerBrick Pro 14.33kwh 48v battery

  • From a previous installation, I also have a Fronius Symo Advanced 15.0.3 that has 15kw of solar panels

    Everything is after the Victron, including the Fronius. When the battery needs charge, it pulls from both the fronius and the mppt at “full power”, with leftovers supplying the house and the excess going into the grid. My issue is when the battery is full. Fronius continues to produce as much as it can and feeds the excess to the grid, while the MPPT stays at low values (a few hundred watts) and sometimes blips to its maximum for a few seconds, while returning. In this time, the battery sits at idle. There is no limit on the grid excess, the voltages are fine, and I am well inside the maximum I can export to the grid.

    I have seen a similar thread where this issue is because of the BMS of the battery, and they way they are implementing CCL vs CVL. But Dyness is in the “approved” battery list of Victron. Before this, after battery was full, the MPPT went to zero, with no generating. The installer switched DC Coupled PV-Feed in Excess to Yes, and it started generating, but I did not watch it closely. Is there something that needs to be switched maybe in the battery or a setting I am missing here? The graph is mostly spikes for the MPPT after battery at 100%, and I know I should be able to produce much more based on the Fronius.

    Any help would be appreciated. Thank you.

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2

This depends on your grid code. Whilst most grids will accept power from AC coupled inverters, fewer will accept power generated from DC sources, as this allows buying cheap power from the grid, storing it and then selling back at a beneficial rate - in my opinion poor planing.

3

I do not think this is the issue. We don’t have dynamic. Price is fixed for both feed in and consumption.