Voltage differences between SmartShunt and Multiplus2/MPPT

StefanR
Thu, 29 Jan 2026 17:37:52 +0000
DIY

Hi everyone!

A quick overview of my system:

3x Multiplus 2 48/5000

4x MPPTs connected via VE.CAN

Cerbo GX

SmartShunt 500A

16 LFP battery cells without a connected BMS

No DVCC configured

AC and DC excess feed-in

Everything connected to AC-in including a Fronius inverter

54.9V absorption, 54V float

I have the issue that the voltage measured by the SmartShunt is always slightly lower (0.1–0.25V) than the voltage shown by the other Victron devices (MP2 and MPPT).
The MP2 even shows a higher voltage when discharging.

I borrowed an additional SmartShunt and connected it at various points in the 48V system: on the busbar, at the MP2s, at the MPPTs, and even tested it without a fuse.
This SmartShunt then showed about ~0.03V more than the installed one.

The lower voltage itself does not really bother me, but apparently it is not used for control in the MP2. So what is the “battery monitor” setting in the Cerbo actually used for? (is set to the shunt)

Because of this, I have the problem that when 54.9V is present at the MP2, the shunt only shows about 54.7V, and the MPPTs go into float mode and drop to zero power, even though AC + DC excess feed-in is configured and the feed-in limit has not been reached.

Does anyone know this issue, or what do you think about it?

Best regards,
Stefan

4 posts - 2 participants