semiraue avatar image
semiraue asked

#67 BMS Connectio lost / Pylontechs are OFF

I have an interesting issue with my off-grid setup:

- 2x 150/45 MPPT chargers
- 1x 100/20 MPPT charger
- 4x Pylontech US3000C batteries
- 1x Cerbo GX controller
- 2x Meanwell TS3000 inverters
- 1x Meanwell NTS450 inverter

Cable from the first Pylontech battery connected to the Cerbo GX, and the setup was working fine. However, yesterday, due to heavy rain, the battery got discharged below 10%. As a result, my home assistance system automatically turned off all non-critical loads (2x TS3000 inverters) and only kept running critical loads.(Meanwell NTS450 inverter)

Today, when I checked, the first battery in the stack (where BMS cable to Cerbo connected) had turned off, and the communication between the Cerbo GX and the battery was lost. The Cerbo GX displayed error #67, indicating a BMS connection loss, and all three MPPT chargers were also showing the same error, causing them to stop charging. This is fully off-grid setup with no other power source available. I have no way to check the battery's SOC, but my critical loads are still running. And later I saw the second battery of the stack also turned off.

To start charging the battery again, I disabled the DVCC (as there was no BMS control), and I had to reset the MPPT chargers to Non-BMS-controlled mode. Now MPPT chargers started working again. However, batteries 1 and 2 did not turn on automatically, while batteries 3 and 4 were on and charging.

My questions are: Do I need to wait for some time for batteries 1 and 2 to automatically turn on? Will the DVCC automatically turn back on?

My setup is monitored remotely, and there is no on-site personnel. I have a camera set up in the location where I can see the batteries and MPPTs

Appriciate your inputs

BMSPylontechlow battery warning
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Alexandra avatar image Alexandra ♦ commented ·


They have turned themselves off. Are there any alarms lights there on them physically?

Usually one part of the Pylon stack wakes up the other. So if that has not happened it won't without intervention.

90% DOD is as far as they want to go. So if you went under that is not great. Have the inverters switch off before then so you don't have the situation again.

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semiraue avatar image semiraue Alexandra ♦ commented ·

Thanks @Alexandra.

Just now I checked all Pyontechs are turned on automatically. Should have wait before posting. But DVCC not turned on automatically. I turned on it manually and set the BMS back to pylontech

90% DOD is as far as they want to go

- Is there a way to check each battery SOC when they stacked ? because one battery is not properly balanced and keep charging always. since I cannot fix it and cannot get replacement I kept it as it is.

I have Home assistant automation to turn inverters off when the whole battery pack reaches 20%. but I still keep another smaller inverter running after this point for equipment like routers and mini server for remote monitoring purpose.

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Alexandra avatar image Alexandra ♦ semiraue commented ·


No they don't send that information to the GX. The only way is the lights on the fronts of the unit. [Correction. The GX does not record or report the individual battery information]

DVCC doesn't have anything to do with one battery waking up another.

Pylons batteries control their own SOC as individuals so they should sort themselves out if there is enough of a charge source to keep them fully charged as a pack long enough.

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1 Answer
Alex Pescaru avatar image
Alex Pescaru answered ·

Hi @Alexandra

The command/response dialog between Cerbo and Pylontech pack also contains the individual battery's state of charge, but probably the guys from Victron choose to not make available that info.

LE: Now I realize that the dialog is over CAN and on that protocol you can "listen" only the pack SOC... Sorry...

Hi @semiraue

You can make/use a simple RS232 module that is connected to the "Console" port of the master battery and you can read from there, through text commands, any information you want from the battery pack, even individual SOC...

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semiraue avatar image semiraue commented ·

Hi @Alex Pescaru,

Thank you for your reply.

Is there any documentation available for the CAN protocol used by Pylontech?

Regarding the RS232 connection, I have a few issues.

Firstly, the battery stack is not located near me, so I would need to send someone physically to connect to it.

Secondly, the Battery View software only displays information for a single battery. Unfortunately, Battery View was also experiencing issues on my remote Windows VM.

As a result, I had to create a small WinForms application to view the battery information and present it in a more user-friendly manner. However, it only displays the information for the battery that I connected via the serial cable.

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Alex Pescaru avatar image Alex Pescaru semiraue commented ·

Hi @semiraue

You can go to Scribd and/or Google and search for "PYLON BMS Protocol - CAN".

As for the Console port, don't use Battery View, just use the plain and simple "pwr" command. It will give you at a glance all pack information. Or use MultiSIBControl software.

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