Problem setting ChargeVoltage eg. current/SoC on Multiplus with MPPT450/100

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1

I am running three synchronized MultiPlus units, two MPPT 450/100s, a battery with a JK BMS, and a Raspberry Pi with Victron OS.

To charge the battery with as little current as possible, I would like to limit the charging current. As far as I can see in the settings, I can only limit the charging current coming from the AC side. Any limitation settings are ignored by the MPPTs.

That’s why I wrote a small “control loop” that adjusts the maximum charge voltage via MQTT so that the charging current does not get too high.

In the diagram, you can see the control working (second graph: blue = target charge voltage from my control, green = actual charge voltage, red = current). From around 08:00 to 09:00, you can see the voltage gradually increasing. This works so far.

Now I want to extend the control so that during summer months the SoC does not constantly stay at 100%, but for example remains around 80%. I also cannot find any setting for this. So my idea was to limit the voltage to a relatively low value to keep the SoC lower “indirectly”.

In the diagram, you can see that the target charge voltage remains constant from about 09:15. However, from 09:45 onwards, the actual battery voltage continues to rise. The Victron system ignores the target voltage from my control.

  1. Why does this happen?

  2. Are there better ways to achieve my goals (adjustable charge current via MPPT and a maximum SoC)?

Victron_ChargeVoltage
Victron_ChargeVoltage1548×432 115 KB

Thanks for your thoughts.

2

Have you tried using the DVCC control in the venus settings?

There is a global charge current and voltage cap that can be set there in the normal UI and is accessible through other methods.

3

I can’t help you with limiting the SOC via voltage, but maybe the way I’m doing it would work for you, if you can export to the grid: I’m limiting the charge current by setting the grid setpoint on dbus (com.victronenergy.hub4/Overrides/Setpoint), via a simple integral controller, and in a second stage, when the SOC is above my target, I’m also using the grid setpoint to discharge (via a proportional controller; this can happen because I have an export limit lower than my max PV power).

This works pretty well for me, with both AC and DC coupled PV.

4

these values are just not used by the MPPTs, they ignore them

5

can’t use that, because my export is limited to 6KW. Although it’s kind of strange that one has to adjust the export to limit the SoC. There should be a way to set the SoC or at least a command to stop charge. But I can’t find that