MultiPlus-II 48/5000/70-50 with Pylontech batteries stops charging at 63%

Q&A and troubleshooting
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1

Hi,
I’m checking an installation with a MultiPlus-II 48/5000/70-50, 8 * Pylontech batteries (total 400Ah, 48V), firmware v3.54 .

We’re not able to get this system charged for more than 63%.
We’ve tried:

  • setting min SOC = 100%
  • grid-feedin to a high value
  • setting: optimised without battery-life
  • equalisation
  • scheduled charge levels
    No high-voltage alarm is raised when charging, low-voltage warnings are raised when discharging.
    Actual CVL=53.2V CCL=165A DCL=200A.
    Battery temperature: 23°C

In VE.configure:
Battery monitor:

  • charge when bulk finished: 95%
  • Battery capacity 400AH
  • Charge efficiency: 95%
    Charger:
  • Curve: fixed
  • Absorption: 52.4V
  • Float: 51V
  • Charge current: 70A

When we ‘play’ with the settings, we can manipulate the system so the battery discharges and charges. But at SOC=63% , 51V, charging stops.
Last SOC above these values date from summer 2025, the system has not been changed since then.

Any idea what is happening? All suggestions are welcome.

Thank You,
Luc.

Additional information, all batteries are detected by Victron, no modules are blocking charging or discharging.

2

I found the answer in another post:
I’ve been reading this thread because it is possible that something that was changed in Venus 3.50 contributes to this. We made an improvement specifically for Pylontech batteries, to ensure that in batteries that are not balanced, we lower the charge voltage to avoid a cell overvoltage problem.

Specifically, the system will attempt to avoid a cell voltage higher than 3.5V, and you can also see that in the chart you posted.

3

Have you updated the inverter firmware?

There is a very high possibility that one of the batteries or two are unhappy.
Pylotech sort of average the voltage and soc.

Correct this is the max cell voltage for a pylon cell.

4

Thank You. I will check the inverter version.
I will also connect Batteryview to check the individual units.