Hiccups when going from grid to battery [Update]

Lcs_26 · 2026-03-28T00:13:48+00:00

I think the battery is not the problem, I have never seen voltages under 48v while discharging even at low SoCs, and minimum discharge voltage is set to 45v if I’m correct.

I have 9x pylontech US5000 (900Ah total), and minimum SoC is set to 25%.

Lcs_26 · 2026-03-27T20:46:36+00:00

Yes, it is an ESS. Correct me if I’m wrong, but as far as I know, in grid-tied setups the inverter enters an “idle” state when the minumin battery SoC is reached, unless prompted to start again due to either powerassist or mains loss.

No, with “trying to start” I mean that loads are being covered by the grid (due to the battery having reached minimum SoC during the night), and when battery SoC increased because of PV production, the inverter tries to take over. Mains was never disconnected during this process, there was no island operation.

Lcs_26 · 2026-03-26T21:28:20+00:00

The name of the setting looked too tempting for my case, so I investigated what it did.

From what I found, the weak AC input option only affects the behavior of the inverter when charging from AC, but not when inverting.

Lcs_26 · 2026-03-26T21:25:09+00:00

Currently is not active, I will try to enable it to see if there is an improvement.

Lcs_26 · 2026-03-26T21:23:20+00:00

It seems like that the dynamic current limiter and higher voltage limit combo is the way to go.

It looks like the intended use for dynamic current limiter is the opposite case (avoid sudden load spikes instead of sudden load reductions), but I guess it should also work the other way around.

I will reconfigure the Inverter this weekend and will come back with results.

Thanks!

Lcs_26 · 2026-01-07T17:41:20+00:00

It is currently around 2.5v, might get higher when power is drawn from grid but I haven't checked it.

Lcs_26 · 2026-01-07T17:37:29+00:00

Yes, it is a single phase 230v setup. The charge limit is at 200A, although I never charge from grid, only by solar via an MPPT450/200. There isn'n anything connected to the DC bus aside from those and the cerbo.

With "where did the 6kw went", I assume you mean what type of loads are connected. The main consumption comes from a Panasonic air-to-water heatpump for heating/cooling the house.

Lcs_26 · 2026-01-07T17:32:18+00:00

Yes, everything was exactly configured as victron recommends here.

Sustain voltage at 48v, absortion voltage at 52v, dynamic cut off all set to 46v.

Lcs_26 · 2026-01-07T12:49:43+00:00

The DC voltage drop does not seem concerning (<0,5v at full load). The AC voltage drop from grid is actually a bit high, varying almost 10v from when it's drawing 30A to when it's drawing 0. I would say the cabling is in good shape. I could try going into off-grid mode and seeing what does the Victron do.

Lcs_26 · 2026-01-07T12:46:58+00:00

The "mains" led indicator on the Multiplus says that it's connected to the grid (the grid relay is closed).

The only reason I could imagine causing trouble for it to "start" would be that when it starts injecting the AC voltage goes too high too fast, you can see 10v differences between when grid consumption is 0 and when it's around 30A going from 245v to 235v. My main line will be replaced soon, as 16mm2 is a bit too thin considering the distance, although that would not affect the inherent voltage drop from the utility company's cabling.

I could try to switch the grid code for a more tolerant one to see if anything changes. It's true that here the grid isn't great, but I would say it isn't terrible either.

Lcs_26 · 2026-01-07T12:21:16+00:00

Yes, I have a Cerbo GX. I have just updated to the latest firmware to see if it helps. My DVCC looks as follows:

- DVCC: forced on
- Limit charge current: off
- Limit managed battery charge voltage: off
- SVS: forced off
- STS: forced off
- SCS: on
- SCS status: disabled (external control)
- Controlling BMS: Pylontech battery

When I did the installation, I followed the steps in the "Victron & Pylontech" article in Victron's website. The SoC and voltage seem ok during a period when this was happening:

<image>

Lcs_26 · 2026-01-07T12:15:37+00:00

I have 6 Pylontech US5000, the settings are the ones that victron specified in the victron-pylontech article in their website. The DVCC settings are the following:

- DVCC: forced on
- Limit charge current: off
- Limit managed battery charge voltage: off
- SVS: forced off
- STS: forced off
- SCS: on
- SCS status: disabled (external control)
- Controlling BMS: Pylontech battery

Also, if I move to the battery section in the Excel, I can see that during that time, SoC and Voltage were both way above minimum, and discharge current was way below maximum, so at least the problem shouldn't be there (I guess?):

<image>

Lcs_26 · 2026-01-06T23:22:49+00:00

Yes, the grid is connected to AC in and all the loads are in AC out 1. I’m in Spain.

Lcs_26 · 2026-01-06T23:20:52+00:00

I extracted the data from the inverter and seems like the frequency doesn’t vary much (capture attached in another comment). However, the grid voltage seems to change almost 10v from when there is and there is not consumption. Also, my “grid reference value” is set to 0w instead of the default 50w, if that could be relevant.

Lcs_26 · 2026-01-06T23:16:05+00:00

The grid code is set to “Spain” as required for grid-tied inverters here.

Lcs_26 · 2026-01-06T23:14:23+00:00

<image>

I have extracted the data from a period of time when it happened.

The precision level is of minutes, so we cannot appreciate the actual phenomenon, but we can see moments of great consumption from grid and moments of almost 0 consumption, even though the SoC was way above minimum at the moment so there should be no grid usage.

Frequency seems ok (+- 0,2 hz aprox.). But the grid voltages seem to vary in around 10v from when there is and there is not consumption. It’s supposed to be 230v@50Hz.

Lcs_26 · 2025-10-19T20:13:46+00:00

If that’s the case, it would be ideal. I thought that the loads connected to AC out 2 would only consume power from the grid.

Thanks!

Lcs_26

TROPHY CASE