I had 12 x 485w Panels feeding a Voltronic Axpert VM IV 5600W 48V installed in October 2023 which has been working perfectly and exactly as expected output wise.
A couple of weeks ago I added a generic Chinese LifePo4 48V 150AH Battery to the Inverter. The Inverter Battery setting 5, was set to Lib (Li-Ion) as instructed by the Battery Manufacturer - all settings are standard LifePo4 apparently, the result was that the Axpert and Battery would not communicate with each other. After consulting the Battery Manufacturer, I adapted a RS485 Cable as instructed and they remotely installed a BMS Upgrade and good news the two are now communicating well except for one issue when Charging with the Inverter set to Lib (Lio-Ion,).
I set the Inverter to Charge at 30 amps as recommended by the Battery Manufacturer and all works well until the Battery SOC gets to around 80% to 85% when it suddenly jumps to 100% SOC and I get an OV message on the Battery LCD. But here is the weird part, the Inverter changes the Maximum Charge Setting from 30 amps down to the minimum of 10 amps and doesn't change back to 30 amps unless you change it back on the Inverter Panel.

The WatchPower App WILL NOT change that one setting and states "Command Failed to Send"  and no matter what happens over time, still won't let me change it back using the App, I can only change it on the Inverter Panel. All other settings I can change on the WatchPower App - no problem.
For your information, I have changed Apl to UPS as a first step.
It is as though the Battery is sending a 100% SOC and then the Inverter say OK - trickle mode only. When the SOC drops just 1% the Battery starts to charge again so there is no communication issue that I can see.
I did one last test and that was to use my own "User Settings" of Maximum Charge 56.2v with a Float Charge of 55.4v and all works well even past 80% and the Charge stayed at 30%. I let it get to 93% then changed the Battery Parameter Setting back from User Settings to Lib (Li-Ion) and after a few seconds the Battery went to 100% SOC and I got an OV message on the Battery. This time the Maximum Charge Current has stayed at 30 Amps.
Finally, on Lib setting, even with full sun and only a 61 watt load, the Inverter is taking only 13 watts from the panels and 57 watts from the Battery.
When I revert back to "User Settings", the panels produce 100% with full sun.
Main CPU Firmware Version 61.01 and Secondary CPU Firmware Version 122.12.
Are there any Firmware Upgrades? I've seen them for the MKS but not the VM model.
Any suggestions greatly appreciated.
 

18 hours ago, SolarTracker said:

the Inverter changes the Maximum Charge Setting from 30 amps down to the minimum of 10 amps and doesn't change back to 30 amps

That's how it's supposed to work. The BMS is telling the inverter not to charge more than 10 A; it knows about the state of individual cells. Unless you go back to manual control, you can't change the charge current settings, and you should not want to. The BMS knows best. Once the battery is discharged more, or balanced more, the maximum charge current will go back up again.

Yup, working exactly as it should.

2 hours ago, Coulomb said:

That's how it's supposed to work. The BMS is telling the inverter not to charge more than 10 A; it knows about the state of individual cells. Unless you go back to manual control, you can't change the charge current settings, and you should not want to. The BMS knows best. Once the battery is discharged more, or balanced more, the maximum charge current will go back up again.

Thank you for the reply -

"Once the battery is discharged more, or balanced more, the maximum charge current will go back up again."

Sorry if my rambling didn't make things clear -

Unfortunately, that is not happening. When set to Lib (Li-Ion), even if the Battery discharges to say 20% SOC, or even if I took it to Zero, the Inverter setting stays at 10 Amps Maximum Charge. Once it changes down from 30% to 10% that's it - stuck at 10% - UNLESS I manually change it on the Inverter Panel.

Also there is the issue of the Battery SOC jumping from around 80% SOC charged when set to Lib, jumping straight to 100% SOC.  When Manually charging it counts up nicely past 85% all way to 100%.

One thing to add is that one Cell appears to be ahead of the rest when on charge at say 3650mv at around 80% SOC when the others are at around 3380mv, could this be the reason for the discrepancy in the SOC? and jumping from 80% charged to 100% charged.  Or is it possibly a BMS programming issue?

Lib settings are 57v for both Maximum and Float Charge but when I set as "User" I use 55.6v Max Charge and 54.8v Float, that also seems to have the effect of reducing the upper and lower Cell charge difference.

15 hours ago, SolarTracker said:

Unfortunately, that is not happening. When set to Lib (Li-Ion), even if the Battery discharges to say 20% SOC, or even if I took it to Zero, the Inverter setting stays at 10 Amps Maximum Charge. Once it changes down from 30% to 10% that's it - stuck at 10% - UNLESS I manually change it on the Inverter Panel.

Ah, OK. I had assumed that it would work like Pylontech, where the inverter completely ignores whatever you set in the maximum charge current setting. That's pretty annoying. I would try updating the firmware, being very careful to choose the right ones. 

Edit: Confused 112.xx with 122.xx. Sigh.

Edit 2: But I don't seem to have any 122.xx display firmware.

Edited January 17, 20232 yr by Coulomb

Thanks again for your comments.

As a well read but fairly newby, could this be the problem when Charging in Lib mode -

The Maximum Charge Rate and Float Rate are both set by the Inverter as 57 volts. This higher Voltage appears to open the gap between the highest charging cell and the lowest.

At around 80% to 85% charge, Cell 7 will be up to around 3650mv which appears to be the maximum I seem to have read about (58.4 volts), so does the BMS say, OK enough 100% charged just because of that one Cell?

The others will be in the 3350 to 3400 range.

Interestingly, if I set my "User" settings lower at say Maximum Charge 55.2 and Float at 54.4, Cell 7 appears far closer to the other cells and Cell 5 has the highest charge but there is only a 20mv difference from top to bottom Cells and the Battery Charges nicely.

The Battery Manufacturer suggests charging at 0.2c of the 150AH which is 30 amps (the actual max tends to be 27 amps).  Would setting it to 40 amps (where the max tends to be 37 amps) to get me to 100% SOC in the shorter Winter months cause an issue with the Battery in your opinion?

Unfortunately, the WiFi on the Axpert VM IV appears difficult or temperamental at times whilst WatchPower or SmartESS isn't as helpful with delayed data that seems to refresh every 5 to 10 minutes.

For an upgrade I'm getting an Orange Pi 3 LTS and going to load Solar Assistant to hopefully manage my setup better and hopefully get a more reliable WiFi connection!!

I have a Second identical LifePo4 battery due in the next month and hopefully spreading the charging load will also settle things down.

"Edit: Confused 112.xx with 122.xx. Sigh.

Edit 2: But I don't seem to have any 122.xx display firmware."

Is the Firmware update worth it in your opinion as the Inverter, Display and charging is all working reasonably well?? apart from my Battery SOC problem.

Your comments are greatly appreciated.

On 2023/01/17 at 7:31 PM, SolarTracker said:

The Maximum Charge Rate and Float Rate are both set by the Inverter as 57 volts.

The maximum charge rate is usually a current, not a voltage. I assume you mean the bulk battery voltage setting. 

On 2023/01/17 at 7:31 PM, SolarTracker said:

At around 80% to 85% charge, Cell 7 will be up to around 3650mv which appears to be the maximum I seem to have read about (58.4 volts), so does the BMS say, OK enough 100% charged just because of that one Cell?

It will say "enough charging for now". Meanwhile, it will try to pull that cell down in voltage, either bleeding off charge into a resistor, or transferring it to other cells. Once cell 7 is back in the normal range, it should start charging again at a lower than normal maximum charge current, backing off that limit (possibly to zero) if cell 7 shoots up in voltage again.

On 2023/01/17 at 7:31 PM, SolarTracker said:

The Battery Manufacturer suggests charging at 0.2c of the 150AH which is 30 amps (the actual max tends to be 27 amps).  Would setting it to 40 amps (where the max tends to be 37 amps) to get me to 100% SOC in the shorter Winter months cause an issue with the Battery in your opinion?

0.2C is pretty cautious, so I think the 40 A limit would be OK.

On 2023/01/17 at 7:31 PM, SolarTracker said:

Is the Firmware update worth it in your opinion as the Inverter, Display and charging is all working reasonably well?? apart from my Battery SOC problem.

Your battery SOC problem seems to be largely a balancing issue. Hopefully that will correct itself in time. If not, you need that cell or the whole battery replaced under warranty.

Hard to say if the update would be worth it, if you could find a suitable update file. It's really easy to get the display firmware wrong, and at present, there doesn't seem to be any VM IV firmware about (main or display firmware). Also, when you move to solar assistant, it will take over the buggy "talk to the BMS" duties.

"The maximum charge rate is usually a current, not a voltage. I assume you mean the bulk battery voltage setting"

Quite correct, my mistake - should have read Bulk not Maximum.

"Your battery SOC problem seems to be largely a balancing issue. Hopefully that will correct itself in time. If not, you need that cell or the whole battery replaced under warranty."

I had come to the conclusion and agree that there is a Balancing issue.

I have already contacted the Manufacturer with regard to possible solutions. Unfortunately, Chinese New Year is currently slowing things down.

In the meantime, I have turned to User Settings and set both Bulk and Float at 54.2v with a maximum charge rate at 30amps. The Battery only charges 90% to 95% but it avoids an OV and the Cells appear to be happier at about 30mv top to bottom and no OV.  I still have 25% to 35% in the Battery in the morning, so am happy not to overstress it.

I'm leaving it like this for a few weeks just to see if Cell 7 continues to behave itself whilst talking to the Manufacturer.

Thanks again.

Hi, I mean from the same problem, and I tried on more than one type of bms, and the problem remained. When the soc reaches 95%, the inverter charger automatically turns to 10 amps, but after discharging the battery to 10% soc, and the inverter starts charging, it remains 10 amps