Since nearly 2+ years my MP2 48/3000 was nicely running with a Li-Ion Battery controlled by JK-BMS and Cerbo-GX.
Last Sunday it stopped operation.
MP2 woundn’t charge any longer and Cerbo-GX says, that one Module is blocking charging:
However when I access JK-BMS I see the following:
Any idea how to “re-initialize” cerbo-GX ?
Rebooting doesn’t help.
Thanks for any hint.
What Chemistry battery are you using? 3.9V is rather high for most LiFePO4 cells..
It’s not LiFePo4.
Should be something with Mn, charging upto 4,2 V/c, it’s 2nd hand usage of a used Twizy battery.
I think you’ll need to tweak the config values in the Serial Battery driver to up the max voltage a bit. The default settings are for LiFePO4
Hi Paul,
I think, when I installed it 2,x years back I did so.
Can you perhaps point me, where to check, honestly I forgot how to access.
Cheers
I don’t know why, but I’ve the feeling, that somesthing is wrong with Cerbo-gx
I’ve seen some report from people, describing ood behaviour.
Does the PuTTY looks okay ?
Where can I find the content of /dev/root ?
I tried to install : sudo apt install ncdu -y to find the files, but venus is refusing installation.
I organized 4 old 12V PB blocs, just to check charging operation of MP2.
how does the 58.8 compare with your expected and current Max battery Voltage? CCL is set to zero, so the BMS is telling the system not to charge.
The Cerbo output looks ok, you can find yhe contents of /dev/root with the ls command., however, it it the contents of /data you need to look at. I would have a look at your BMS configuration, as it looks like that needs updating.
I searched a bit araound, and found the JK-BMS at this location:
when I look in config.ini:
MAX_CELL_VOLTAGE = 4.200
which comes to 4,2 V/c * 14 = 58,8 V.
Yesterday I tested an 4 old 12 LA blocs, to avoid any interference with the BMS.
I’ve the feeling, the MP2 might be not okay - but not 100% sure.
Your MP2 charge voltage settings should be the same or higher than the maximum battery voltage desired, as otherwise as you have found, this will limit the charging. With old lead batteries, the charge current is often very limited due to sulphation. This does not mean that the charger is faulty.Similarly when discharged the voltage also drops rapidly.
So you need to set the Abs voltage in the MP2 to 58.8V, Float to 54.6V. Also set these value in any MPPT on the system.
Your MP2 charge voltage settings should be the same or higher than the maximum battery voltage desired, as otherwise as you have found, this will limit the charging.
Fully right, when the system was running a second Battery (LiFePo4 (Pytes E-Box)) has been connected in parallel, that’s why the MP2 voltage settings are currently lower - but it doesn’t explain the behaviour.
With respect to aging of LA I disagree. Normally they consume more power and turn them into losses (heating). And the sharp voltage drop can’t result from the battery, even when old, unless internally broken.
Today I realized with some further testing, that it takes “hours” for the MP 2 >charger< to sync and start-up. Our (home) grid is stable and it’s makes me wondering, too.
Anyhow, tomorrow the unit goes to service and I’ll gona report.
My personal guess, an internal “fuse” or “semiconductor” got blown up - for what reason whatsoever.
Thanks for trying to following me, good to know someone is out there 
Internal sulphation dramatically increases the internal resistance of a lead acid cell, and is the most common failure mode of old batteries.
You’re right, my fault.
When testing of the LA battery however, it provided approx. 11 Amps on the resistive load, while the charger provided just about 200 W.
Thus when charging, I would assume about a similar (at least above 400 W) value.
Anyhow, I’ll letcheck the unit and I/we know more.
Problem solved !
MP2 was checked and found okay.
Now I checked again my wiring. I’m using a NH00 fused breaker with cover to finger protect the bolds for the cables.
And for whatever reason, one bolt get loose and the cable lost firm contact.
Next time, I really check all cable not twice, but three times.
