MultiPlus II not powering DC loads from grid

Q&A and troubleshooting
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1

Hello,

My MultiPlus II 48/5000/70-50 does not supply power to the DC loads. Is this normal and expected behavior? Or do I have something misconfigured?

I believe my system setup is somewhat unusual, which might be causing the issue.

Here’s my system configuration: three-phase 3x400V supply protected by a 32A breaker. One MultiPlus II 48/5000/70-50 is installed on phase L1, configured with the ESS assistant. On the grid side, I have a VM-3P75CT meter installed so that the system can correctly measure loads located before the MultiPlus AC-IN. Several backup loads are connected to AC-OUT 1, while the rest of the loads are on the AC-IN side. The AC-OUT 2 output is not connected.

The system includes photovoltaic sources on both the AC-IN side of the MultiPlus (two Hoymiles microinverters on phases L2 and L3) and the DC side, where one SmartSolar MPPT 150/100 is used. Everything works great — I have no complaints about the ESS operation. The DC-coupled PV - feed in excess option is enabled and functioning well. Additionally, the ESS is configured with a Grid Set Point of -10W, which it maintains most of the time without issues.

The problem appears under specific conditions. When the battery state of charge (SOC) drops to the minimum level set in the ESS settings, the MultiPlus starts powering all loads directly from the grid — as expected.

The issue is on the DC side. The MultiPlus does not supply power to DC loads, allowing the battery to discharge below the minimum SOC threshold. If the SOC drops about 5% below the minimum limit, the MultiPlus starts recharging the battery from the grid at the full charge current limit set in VE.Configure. This cycle can repeat 2–3 times per day.

In my system, many loads are connected directly to the main battery via a SmartShunt 500A, which is configured as a DC Load. The Cerbo nicely reports DC loads, which typically range from around 130W up to over 1000W at peak.

What should I configure so that when the battery reaches the minimum SOC threshold, the MultiPlus powers my DC loads from the grid instead?

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@tstiller It is not a problem. A Multiplus does not directly power or even consider DC loads, but will charge the battery from AC if it reaches e.g. a set min SOC or voltage threshhold. Actual DC loads are of no consequence to the system, other than accounting for a missing component using the DC Load setting to display it or maybe through a shunt. Simply put, if the battery is 100% yet the system sends a fair amount of energy to the battery, it is likely because there is an unaccounted for DC load component which you can elect to display.

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So it’s a feature, not a bug?

To me, this feels like a problem. It’s hard to believe that the Victron system would completely ignore DC-side loads. Is the extra Smart Shunt set up as a DC Load there just to monitor energy usage?

That’s the part I don’t really get. The system has all the info it needs to balance those loads — so why doesn’t it do it? All my loads are connected behind the Smart Shunt, and the batteries go through the Lynx Shunt. Both devices send their data to the Cerbo.

Since the Cerbo can see those loads, in theory the system should be able to compensate for them just fine. The MultiPlus could simply raise the DC voltage on its side until the battery stops discharging. From a technical point of view, that really shouldn’t be an issue.

On cloudy days, my system can drain the battery twice a day — about 5% below the minimum SOC threshold — which triggers basically uncontrolled grid charging once the SOC drops to that lower level. I know I can set up timed grid charging, but that really shouldn’t be necessary. Why put extra strain on the battery when the Multi could just power the loads directly through its charger?

Maybe I haven’t explained my issue clearly enough. All my loads are measured correctly — both on the AC and DC side. Nothing is missing, and the DC load I mentioned is expected in my setup. On the DC side, I’m powering all the lighting in the building plus some networking equipment.