I would like to have the following safety function in CerboGX. There should be the option to enter a limit for the maximum cell voltage transferred by the BMS. When the limit is reached, the charging current should then be regulated. As long as only the maximum charging voltage can be limited in the DVCC, it is still possible for individual cells to exceed the maximum value.
Sounds like you need a better BMS. The system is managed by the BMS, and it is the BMS’s responsibility to prevent cell over-voltage. The way to control this properly is via regulating the pack voltage, not current control.
This isn’t necessary on the majority of batteries, though, is adjusted on one brand which is more sensitive to high voltage alarms. Two or more major brands already do dynamic voltage control, while on others, this just isn’t a problem.
For DIY systems, you have the ability to customise the BMS profile.
Personally I can’t see this ever happening.
You do have the ability to do this via nodered or custom coding.
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Hi @Stromhamster
Is your BMS reporting the maximum and minimum cell voltages?
If yes, did you take a look at this topic?
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@nickdb
I guess I didn’t express myself correctly. Active current regulation by the Cerbo would not be the goal. When the max. charging voltage stored in the DVCC is reached, it regulates the chargers. A max. cell voltage value could trigger the same process. I can configure my BMS parameters myself, but I have battery packs that only work with passive balancing. If the DVCC limit is reached, there is no balancing because no more charging current flows. The Cerbo does recognize the charging current flowing to the battery and could therefore also adjust it via the voltage regulation. Victron experts in the forum often recommend reducing the max. charging current in the DVCC if users are struggling with overvoltage problems. So why not specify a min value when the max. charging voltage or max. cell voltage is reached?
@alexpescaru
Thanks for the tip, I’ll have to read a lot first and see what’s possible for me.
The current Pylontech “quirk” implemented in the 3.50~20 is doing exactly what you are looking for.
When the max cell voltage set inside the script is reached, then the algorithm starts to regulate the charging in order to not allow the “runaway” cell to still increase its voltage.
The other algorithm presented is viewing the problem from the opposite angle, slowing down the charging by following instead the “slowest” cell (min cell voltage) and waiting for those “slower” cells to catch up.
If you don’t have a Pylontech, you may still implement one of these algos into the same dvcc.py script.
@alexpescaru
Hello Alex, I created my own solution using Node Red. This means I don’t need to install any scripts.
I regulate the max. charging current and the max. charging voltage using Max-Vcell.
Unfortunately I have one (out of 64) bad cell which drifts over 200mA, all the others have around 20mA when the battery is full.
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