.

Edited April 28, 20242 yr by jbroo

36 minutes ago, jbroo said:

I'm fairly handy with a soldering iron and a resistor chart so if I can figure out where these are, I will change them, provided they are indeed the culprits.

They are usually pretty obvious, as they will often be a pair of 3-6 (often 4) medium sized SMD resistors in series, with the ends kept close together (so they get affected about the same by noise), and often they are covered in "silk screen" (I doubt that silk is actually used any more):

Note the battery fuse nearby (they look different these days, sometimes just necks of metal), and near the battery terminals. These have 1004 marking (1.00 MΩ each), more commonly they are in the high hundreds of kilo-ohms.

With your wildly varying results, I think it's worth checking these first. Test with heat and cold, as well as gentle pressure on the PCB.

24 minutes ago, Coulomb said:

Test with heat and cold, as well as gentle pressure on the PCB.

Thanks! It could indeed just be cold solder joints in need of a re-flow.

Update: It was somewhat accurate in the beginning, but it keeps drifting further with each day...

Note the battery overvoltage fault. SCC voltage remains accurate.

@Coulomb it was not the resistors. Through sheer endless trial and error I've figured out the calibration procedure, for the most part:

1. Issue PSDF to clear and begin calibration.
2. Issue PMID (still not sure what this does exactly).
3. Turn off mains and load on the inverter and power it off.
4. Power it back on, turn on mains supply and load.
5. Turn off mains supply and let your batteries drain to as low as you're comfortable with, but preferably a few volts lower than your "high" reading.
6. Turn on the mains supply, charging should begin.
7. Issue PBATLnnnn where nnnn is your low voltage, as soon as possible, when the reading on your meter has stabilized. Important: ensure your mains is connected when issuing this.
8. Issue PSAVE.
9. Get your battery charge level as high as possible. You may need to force a charge by using equalization or set bulk charge to max (30V).
10. Issue PBATHnnnn where nnnn is your high voltage - important: ensure your mains is connected when issuing this.
11. Issue PSAVE.
12. If all went well, your battery (and SCC) voltage should now be in line with your meter. If you bumped up your bulk, float and equalize voltages to force a charge, now is the time to set them back to their proper values.
13. Optional: Issue CF11 and PBFnnnn where nnnn is your voltage on the meter with both fans on. Follow this with PSAVE.

The crucial point that I found out, is to never try to set the voltages without mains connected - I was doing this when setting the low voltage (turning off mains and waiting for the batteries to discharge sufficiently). This is what was causing my voltages to be out of wack. Always turn the mains on after discharge and set the low voltage as soon as possible thereafter.

Happy tinkering.

 

Edited May 24, 20242 yr by jbroo

Hello, I was wondering if the settings you shared are still working properly. I am experiencing the same issue.

The PBATH and PBATL only work with certain smaller models. An Axpert Max will need to use the BTA commands.

Could you share which application to use and which command to execute?

On 2023/08/27 at 8:53 AM, Coulomb said:

Sigh. It seems I was wrong about the PBATH and PBATL commands. It seems you have to send these three in order:

PSDF

PBATLnnnn

PBATHnnnn

Internally, the PSDF sends a BTA0 command to the solar charge controller's processor, PBATL sends a BTA1, and finally PBATH sends a BTA2. I haven't checked whether the solar charge controller can cope with the commands out of order, but it seems sensible to send them in the order such that the solar charge processor gets BTA0, BTA1, and BTA2 in sequence. Probably BTA2 is the one that actually calculates the new scale and offset in the SCC, so it's important to get that right as well.

I had suggested sending the commands in the other order, and said that the order doesn't matter.

My guess is that this added enough chaos to the situation that things never made sense, and that's why the readings seem to get worse rather than better.

So (at least at this stage), it would seem that there is no need to lie about the multimeter reading.

I hope that this helps with your calibration.

It also shows the importance of reporting  when things go wrong, so that instructions like this can be corrected. So thanks for that feedback. Hopefully others can get their calibrations right now.

And sorry for the bad information, and the frustration that it caused.

I try this isn't working what the problem?

On 2023/08/27 at 8:53 AM, Coulomb said:

Sigh. It seems I was wrong about the PBATH and PBATL commands. It seems you have to send these three in order:

PSDF

PBATLnnnn

PBATHnnnn

Internally, the PSDF sends a BTA0 command to the solar charge controller's processor, PBATL sends a BTA1, and finally PBATH sends a BTA2. I haven't checked whether the solar charge controller can cope with the commands out of order, but it seems sensible to send them in the order such that the solar charge processor gets BTA0, BTA1, and BTA2 in sequence. Probably BTA2 is the one that actually calculates the new scale and offset in the SCC, so it's important to get that right as well.

I had suggested sending the commands in the other order, and said that the order doesn't matter.

My guess is that this added enough chaos to the situation that things never made sense, and that's why the readings seem to get worse rather than better.

So (at least at this stage), it would seem that there is no need to lie about the multimeter reading.

I hope that this helps with your calibration.

It also shows the importance of reporting  when things go wrong, so that instructions like this can be corrected. So thanks for that feedback. Hopefully others can get their calibrations right now.

And sorry for the bad information, and the frustration that it caused.

I try this isn't working what the problem?

Did you send an ATE1 command first? That allows all commands through to the DSP. This is necessary for certain lesser-used commands. Send an ATE0 after you're done with the calibration, to return the display operation to normal.

Also, only some inverter models use the PSDF command. See my battery voltage calibration post.

Hello Mr,

Could you please give the latest version for voltronic vmiii 4kw inverter.

my inverter versions:

Main CPU: 60.08

Secondary: 25.12

On 2025/06/10 at 10:45 AM, omar198 said:

Could you please give the latest version for voltronic vmiii 4kw inverter.

my inverter versions:

Main CPU: 60.08

Secondary: 25.12

The latest 60.xx firmware for VM IIIs and IVs 4 and 6kW Twin that I know of is 60.10, July 2024 versus March 2024 for 60.08.

If you want the quietest fans, you likely have to go backwards a few months to 60.95 (January 2025).

The latest 25.xx firmware for VM III touch button displays that I know of is 25.16 (August 2024), compared with 25.12 from November 2023.

60.10 and 25.16 are available here:

Patched firmware versions x60.10 are available a few posts after the above.