Hi everyone,

I have a Voltronic VM IV 3.6Kw with 5x550W solar panels installed in series. I've been monitoring the PV power and trying to maximize the PV production but the PV input never seems to stablize even on a clear sunny day, stable load and charging batteries. It keeps fluctuating no matter what, and my maximum daily PV production has never exceeded 12Kwh (is this normal for a 2.75Kw system ?). I've attached some screenshots of today's inverter data which was a very sunny day. Could it be a bad MPPT charge controller ? a firmware bug ? any idea ?

Thanks.

12 hours ago, RoyS said:

a firmware bug ?

Strangely, I've not seen a single firmware update file for the Axpert VM IV model. Maybe it's perfect and doesn't need any fixing? 🤔

3 hours ago, Coulomb said:

Strangely, I've not seen a single firmware update file for the Axpert VM IV model. Maybe it's perfect and doesn't need any fixing? 🤔

My firmware version (61.02) has lots of quirks that I'm willing to live with but the mentionned behavior and low efficiency is a show stopper. I find it hard to believe that all VM IV have the same problem and tend to think I may have a defective unit that can be repaired maybe by replacing the MPPT or some defective components in it?

The weird thing is that the inverter PV power doesn't fluctuate early in the morning but only after it has reached around 600-700W and the panels voltage is well within the MPPT range.

What do you think ?

On 2023/07/16 at 7:09 AM, RoyS said:

my maximum daily PV production has never exceeded 12Kwh (is this normal for a 2.75Kw system ?).

That's actually pretty good. One would hope for about 5 "full time hours of sun equivalent" in summer, 4 is doing well in winter. You can only expect to get 75-80% of rated power from panels, except for brief moments. So call that 2.1 kW; that's 8.4-10.5 kWh. So I don't think that you're losing a lot of production, despite the strange oscillations.

13 hours ago, RoyS said:

The weird thing is that the inverter PV power doesn't fluctuate early in the morning

Maybe it's temperature related then. Do the fans come on with solar charging? Oh wait, VM fans are probably running all the time.

My wild guesses are a thermal intermittent fault in the MPPT, or early firmware version. 61.02 does sound fairly early, and they certainly have had problems with MPPT control. Despite that, you don't seem to be suffering from the "stuck at 120 V" problem.

Edit: Though the fact that the solar charge power doesn't dip to zero suggests that the MPPT hardware is working. So that leaves firmware, if it ever becomes available.

Edited July 17, 20232 yr by Coulomb

3 hours ago, Coulomb said:

That's actually pretty good. One would hope for about 5 "full time hours of sun equivalent" in summer, 4 is doing well in winter. You can only expect to get 75-80% of rated power from panels, except for brief moments. So call that 2.1 kW; that's 8.4-10.5 kWh. So I don't think that you're losing a lot of production, despite the strange oscillations.

Thank you @Coulomb for the detailed explanation!! It's a relief that the production is normal and the numbers I have are in line with your calculations (Production of the last 30 days in the attached image).

I will try to experiment more with the different settings and maybe test a different inverter in the same setup. I will update this thread with the results, hoping one day they will release an updated firmware for the VM IV which solves this problem, without introducing new bugs!

Cheers

With all the OEM and different versions of these Voltronic inverters, how do know exactly what you have ?

Mine is labeled as VM IV and its serial number starts with SG96322 but it's red with a square LCD, not white and a round LCD like on the Voltronic website.

I emailed the brochure to Voltronic sales when I first got it and the representative told me it's their 2020 special version.

Today, I ran the QMN command and the result was VMIII-3600 !!!

 

11 hours ago, RoyS said:

how do know exactly what you have ?

It's a significant problem, and one that Voltronic aren't as helpful with as one would like. Generally, the sticker is the best guide, but it still doesn't tell you some important things,  like is it a 64 V model.

11 hours ago, RoyS said:

its serial number starts with SG96322

It's unusual but not impossible for a genuine rebranded model to have a serial number that starts with two letters. 9632 as the first 4 digits is close to some that I've seen, but not equal to any. The last 2 is the first digit of the year code, i.e. 202x.

11 hours ago, RoyS said:

I ran the QMN command and the result was VMIII-3600 !!!

Yes, this is really annoying. I think that did that so that it didn't break some monitoring software. It's also really annoying that the VM series don't support the QGMN command that almost all other models support (Query General Model Number), and that these model numbers are inconsistent and not documented.

Edit: Actually, QGMN model codes are not completely undocumented; I have a protocol document that lists the models up to 034. But that doesn't include any recent models such as the Axpert MAX or Axpert VM IV.

Edited July 23, 20232 yr by Coulomb

1 hour ago, Coulomb said:

It's also really annoying that the VM series don't support the QGMN command that almost all other models support (Query General Model Number), and that these model numbers are inconsistent and not documented.

Actually mine does and it returns "048". Is that a model number ?

9 hours ago, RoyS said:

mine does and it returns "048". Is that a model number ?

Yes, it's a model code. My notes say "Axpert Max II 8kW 230V" with a question mark. I don't have any Max II 8kW firmwares, so I don't know where I got that idea.

Actually, QGMN isn't totally undocumented, just the latest and most useful values. I have a protocol manual that shows what they mean up to 034. It has no mention of VM IV. Axpert VM III is 027. 

I have finally managed to solve the problem by adding just one more solar panel!

My setup consisted of 5x 550 W TrinaSolar panels. These panels have a Voc of 37.9 V and a Vmpp of 31.6 V totaling 189.5 Voc and 158 Vmpp well within the MPPT range of the inverter (120-450 V) but for some reason it was struggling to keep a steady PV Power.

I just added one 555 W panel of the same model in series so the total Voc is now 227.6 V and total Vmpp = 189.8 V. The improvement was immediate as clearly visible in the graph below.

 

 

41 minutes ago, RoyS said:

I have finally managed to solve the problem by adding just one more solar panel!

My setup consisted of 5x 550 W TrinaSolar panels. These panels have a Voc of 37.9 V and a Vmpp of 31.6 V totaling 189.5 Voc and 158 Vmpp well within the MPPT range of the inverter (120-450 V) but for some reason it was struggling to keep a steady PV Power.

I just added one 555 W panel of the same model in series so the total Voc is now 227.6 V and total Vmpp = 189.8 V. The improvement was immediate as clearly visible in the graph below.

 

 

Good to see you are satisfied with the improvement upping the start voltage. The output now compared to your daily yield in mid July(about 8kWh) appears to be the same. 

Do I miss something? 

I also think what we see some MPPTs are indicated that the start voltage is 150+-10V. We should thus not rely on starting at 150V at all times. 

Thanks. I was worried about the fluctuations in the battery charging current shortening the life of the batteries.

I need to monitor the daily yield for some time to check for improvement, as it's only been one day since I added the panel. I would be surprised of that didn't drastically improve.

 

Edit: The yield yesterday was 10.3 kWh and the batteries were already full so I'm beginning to notice some improvement.

Edited August 5, 20232 yr by RoyS

On 22.07.2023 at 17:14, Coulomb said:

Este o problemă semnificativă și una cu care Voltronic nu este atât de util pe cât s-ar dori. În general, autocolantul este cel mai bun ghid, dar tot nu vă spune câteva lucruri importante, cum ar fi este un model de 64 V.

Este neobișnuit, dar nu imposibil ca un model rebranded autentic să aibă un număr de serie care începe cu două litere. 9632 ca primele 4 cifre este aproape de unele pe care le-am văzut, dar nu este egal cu oricare. Ultimele 2 sunt prima cifră a codului anului, adică 20 2 x.

Da, asta este cu adevărat enervant. Cred că a făcut asta pentru a nu strica niște software de monitorizare. De asemenea, este foarte enervant că seria VM nu acceptă comanda QGMN pe care o acceptă aproape toate celelalte modele (Query General Model Number) și că aceste numere de model sunt inconsecvente și nu sunt documentate.

Editare: De fapt, codurile de model QGMN nu sunt complet nedocumentate; Am un document de protocol care listează modelele până la 034. Dar acesta nu include modele recente, cum ar fi Axpert MAX sau Axpert VM IV.

How i can command QGMN on Easun 8kw? I want to see what s in the back

 

Probably the easiest way, if you have a Windows machine, is to use the Communications Tool from Voltronic themselves. It does the CRC calculation automatically.

Available from:

https://www.mppsolar.com/v3/download/

and search for "Communication Tool".

You will of course need a USB to serial adapter and the correct cable; same as the ones mentioned in the firmware upload instructions.

As a final update about this issue, the daily production increased drastically after adding one additional solar panel. A few days ago the daily yield was 14.4 kWh and could have been potententially higher than that if we had increased the load in the afternoon (Graph below).

Lessons learned:

1. A monitoring system like Solar Assistant is a valuable tool to check the efficiency of the system and troubleshoot problems.

2. Although inverter vendors specify an operational MPPT range in the specifications, one should target the center of this range for the best performance.

3 hours ago, RoyS said:

As a final update about this issue, the daily production increased drastically after adding one additional solar panel. A few days ago the daily yield was 14.4 kWh and could have been potententially higher than that if we had increased the load in the afternoon (Graph below).

Lessons learned:

1. A monitoring system like Solar Assistant is a valuable tool to check the efficiency of the system and troubleshoot problems.

2. Although inverter vendors specify an operational MPPT range in the specifications, one should target the center of this range for the best performance.

Good that you seeing good improvements with the extra panel. Some time ago @Coulomb indicated that your yield was not too bad and actually good. At that time production in summer could have been 2.2kw(80%) peak and you got 1.8kw which is good for winter.

Since the beginning of the early July post the daily yield are just going up every day. Yesterday I had the best yield since mid April. 

Today the clouds have arrived and effecting yields quite a bit. 

Hi everyone. I have the same problem but with Powmr POW-HVM PRO 6.2M-48V. But it's only fluctuate when SUB mode enabled and when at export to grid, in SBU mode works flawlessly without drops, and PV power always at highest point(SBU). My setups is 6x545 Longi solar(Short-circuit current 13.92 A, Open circuit voltage 49.65 V).

Please check PV current, voltage, and power production on attachments(it's sunny day without clouds).

Hope some one can explain such behavior.

Thanks

Edited January 12, 20242 yr by Flyzet

Hello everyone,

I’m new to the topic, i recently purchased a Voltronic Axpert Max II 11kw and I noticed the same 90v issue under cloudy days.

The versions that I have are the below,

U16304

U22224

U30000

There is currently any new firmware to solve this issue?

Thank you for your support.

On 2025/02/21 at 7:07 PM, Chpedro93 said:

Hello everyone,

I’m new to the topic,

Welcome to the forum. You've posted in the wrong thread; this one is about VM IVs. So don't be surprised if a moderator moves it and this reply.

On 2025/02/21 at 7:07 PM, Chpedro93 said:

i recently purchased a Voltronic Axpert Max II 11kw and I noticed the same 90v issue under cloudy days.

The versions that I have are the below,

U1 63 04

There is currently any new firmware to solve this issue?

Alas, there are no Axpert Max II 11 kW non-Twin firmware updates available, as far as I know.

Some recent firmwares do a better job on the MPPT algorithm, others still need patching. I can't patch without a firmware update to base the patch on. Sorry!