question

Hi Alexandra. You are right, DVCC successfully recognized both Pylon/Multi and let Pylon drive the inverter. I only followed instructions on Victron site to limit Absorption voltage with means of VictronConnect and MK3 interface. I assume it can help if Cerbo disconnects for some reason. I remain curious why Pylon goes in idle when charged with 10A or less? Should I look into the battery settings and/or upgrade its firmware?

Charger tab

What I've suggested is extracted from the Victron's source code.

It's a thing that is already implemented by Victron for Pylontech batteries.

For sure I can (now) explain it in detail, thing that, no offense, no one tried here: https://community.victronenergy.com/questions/269636/debugbatteryoperationallimits-usage.html

Small quote from a comment inside dvcc.py file/script, :

# Do the same for 24V batteries. The normal limit is C/2, so put the 
# limit to C/4. Note that this is just a nicety, the important part is
# to clip the charge voltage. That also fixes the sawtooth issue.

Root cause is on nobody side.

Pylontech request CCL=0 when SOC=100%. Which Victron respects, by stopping its charger.

Problem is that when the charger stops, a small current is still drawn from batteries for various reasons.

A small part by the Multiplus own electronics, another part for when a sudden variation on load appears and Multiplus tries to supply it by consuming from battery and so on...

This will lead to a small decline in the battery voltage and SOC up until it hits 99% and then the Pylontech communicate a CCL different from 0 and the Multiplus feel the need to top it back until Pylontech says again CCL=0.

What is implemented inside Victron code is a way to keep the charger active and to supply a small current to Pylontech in order to compensate with the loses and to keep the float voltage steady. Also used when feedback is allowed, but this is not your case.

Pylontech says charge the battery with voltages between 52.5V to 53.5V. Your 51V float will be well below the Pylontech's specification and if someone will keep the battery permanently at a constant 51V voltage will not void Pylontech's warranty. In fact that bulk, absorption and float terms are relics from the age of flooded batteries. With LiFePO4 batteries only a voltage and a current (both specified by BMS) should be respected. Charge with no more than specified CCL in Constant Current mode until CVL. Then you can keep at CVL indefinitivelly in Constant Voltage mode. The rest is done by Kirchhoff laws and BMS.

Even if you keep the charger active with a current limit / offset, for example 5 amps, once the voltage at the battery / charger terminals reach the set float voltage, the current will reduce to almost 0 or at the level it's needed, compensating that small current draw that makes the SOC decline.

Yes, the setup is certified by pylon and victron. Your warranty is based on this.

There is no issue with this minor variance of SOC.

Deviating from the config will void your warranty, so trust the manufacturer and use their setup. There are many, many installs with pylons. It works. You don't need to mess with it.

Degradation happens, that minor variation isn't a major factor beyond time and temperature, which have a greater impact.

On a properly sized system, variations shouldn't happen that often.

Hi @Nokiamade

I've tried to explain it above where you've asked for root cause.

That isn't something currently available on the community.

As a Victron community we have a responsibility to ensure members, especially new ones, get the full picture, and fully understand what they are trying to do. You are welcome to mod your system as you choose, it is at your own risk.

The setup docs are tried and tested, they are what your warranties are based on. if you choose to deviate, just understand you are trying to fix a problem that does not exist and ultimately will be unsupported.

Your query is best had with pylontech support.

Feel free to discuss modifying your setup, just be aware that you will be on your own if it doesn't work as expected.