Issue with Charge Current Overshoot in Parallel MultiPlus-II System

DIY
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Subject: Issue with Charge Current Overshoot in Parallel MultiPlus-II System

Dear Victron Energy Technical Support,

I am reaching out to you directly because my equipment was purchased in Germany, and the local official dealers in Ukraine are refusing to provide technical support for it.

My System Configuration:

• Inverters: 2 x MultiPlus-II 3000/35 (connected in parallel, Master/Slave)

• System Control: Cerbo GX

• Batteries: 2 x Dyness 5.0 Pro (connected via CAN-bus, DVCC enabled)

VRM Access Details:

• VRM Portal ID: (moderated)

• VRM Installation ID: 887874

• I have enabled Victron Support access in the VRM settings so you can check the system logs, overshoot graphs, and current DVCC configuration.

Problem Description:

I am experiencing a severe temporary charge current overshoot at the beginning of the battery charging cycle. The inverters fail to hold the set current limit from the very first seconds; instead, they significantly exceed it before stabilizing.

Symptoms:

1. If I set the charge current limit to 55A, the inverters abruptly spike the current up to 70A at the start of the charge, and only after that do they smoothly reduce it to the target 55A.

2. If I try to increase the charge limit (to utilize the potential of both batteries), the initial current spike exceeds 80A.

3. Additionally, on the Cerbo GX widgets, I can see that the Dyness BMS is transmitting a Charge Current Limit (CCL) of exactly 80A. Why is this specific limit set by the BMS, and why does the Victron system overshoot it instead of respecting it?

4. As a result of this overshoot surge, the battery BMS detects an Overcurrent, disconnects the contactors, and the entire system goes into an alarm state (VE.Bus Error / Low Battery).

Currently, I am forced to artificially restrict the charge current to 55A so that the initial spike does not trigger a system crash.

Questions:

1. Is this short-term current overshoot at the start of charging a characteristic hardware behavior for a system consisting of two parallel MultiPlus-II inverters, or is this an anomaly that needs to be corrected?

2. How can I smooth out the charge start curve so that the inverters gradually increase the current, strictly without exceeding the set limit? Are there specific settings in VEConfigure or hidden regulator parameters in the Cerbo GX (e.g., in the DVCC section) to fix this?

Thank you in advance for your assistance.

Best regards,

2

Have you used the VE-configure tool to reduce the max charge current in the inverters, or are you using the “limit max charge current” in the Cerbo?

I run 2 inverters in parallel, and don’t have this problem, though the system set up is different. The charge current is limited in the inverters due to small generator size.

The VE-bus feed back takes some time to settle, hence the overshoot, if the current is not limited directly in the inverters.