On 2021/08/29 at 12:57 AM, Beat said:

But after a number of such cycles the inverter with the 9 PV panels remains with the panels switched off whereas the other one continuous working correctly. I thought that this is an inherent fault of that unit. So I swapped the panel arrays connection between the inverters. To my great deception the fault had also gone to the other unit.

 

On 2021/08/29 at 12:57 AM, Beat said:

The large array (3s3p) outputs around 110V at full power, the small (3s, different type of panels) only around 90V.

That could be part of it. In my signature, I do say If using 72-cell panels with a 145 V max solar charge controller, 2S often works better than 3S." (Actually, it had it around the wrong way, to my profound shame). If they're at 110 V under load, then they'll be at some 120+V open circuit (e.g. after the change to float stage), and this is outside the 60-115 V MPPT range. So that might cause them not to come back on.

In the mornings, when the sun is weaker, they might not exceed 115 V, and besides they will be under load immediately. So that's why the work in the morning.

So all you need to do is to rewire them from 3S3P to 2S4.5P 🥴!  To see if this is really the issue, perhaps you could place some load on the 3S3P panel set (say a 240 V incandescent bulb), and if that reduces the open circuit voltage below 115 V, the panels might come back. I'm hazy about the 115 V limit, so don't go to huge efforts here. Another thing would be to see if cloud reduces the voltage below 115 V for a minute or so, and if that causes them to come back. You might even be able to go through some recent logs to see if this situation happened before.

[ Edit: 4.5S2P → 2S4.5P. Duh. ]

Edited August 30, 20214 yr by Coulomb

I have a pair of IPS 4000WM inverters that previously paralleled just fine,  Now that I've moved them due to the upgrade to lithium, they don't want to play ball.

Previously I was not using the Solar Charge controllers.  Both worked fine initially now they cycle the fans and read about 5 volts low on the PV (68 VDC instead of 73VDC).

I've ordered a stand alone Solar Charge Controller for now.  The lack of Parallel capability is more of a chore for me.

As I work through the problem I will post results and if anyone has some insight that will make it easier I would appreciate the feedback.

 

Modelmakeroz.

 

Mackay Qld AUs

 

15 hours ago, Coulomb said:

 

That could be part of it. In my signature, I do say If using 72-cell panels with a 145 V max solar charge controller, 2S often works better than 3S." (Actually, it had it around the wrong way, to my profound shame). If they're at 110 V under load, then they'll be at some 120+V open circuit (e.g. after the change to float stage), and this is outside the 60-115 V MPPT range. So that might cause them not to come back on.

So all you need to do is to rewire them from 3S3P to 4.5S2P 🥴!  To see if this is really the issue, perhaps you could place some load on the 3S3P panel set (say a 240 V incandescent bulb), and if that reduces the open circuit voltage below 115 V, the panels might come back. I'm hazy about the 115 V limit, so don't go to huge efforts here. Another thing would be to see if cloud reduces the voltage below 115 V for a minute or so, and if that causes them to come back. You might even be able to go through some recent logs to see if this situation happened before.

Thank you, Coulomb, for your hint. I am afraid you are right. I did not pay attention to that Operating voltage limit. I thought to be within the 145V OC voltage would be save. Neither did the seller/installer of the system. As a matter of fact the OC voltage at floating procedure goes up to around 130V!(WatchPower reading) However, surprising is that it works well a couple of times before failing.

Now what to do about it? Rewiring is not an option. It would also require stronger than 6mm² wires for the increased current. Besides, how do you 4.5s? I'm thinking of a device that becomes active at 114V and connects to a load. I could think of a 24V relay with a 90V Zener diode on the coil. But I'll try the incandescent bulb trick. I have an old spotlight 100W 230V left.

Is there a way to program the "dry contact relay" to give me a signal when cutting the panels out for floating procedure?

4 hours ago, Beat said:

Now what to do about it? Rewiring is not an option. It would also require stronger than 6mm² wires for the increased current. Besides, how do you 4.5s?

The best answer would be to rewire as 2S4P, making a panel redundant, or 2S5P, adding another panel of very close to the same characteristics (especially Vmp and preferably also Voc). You would need multiple cable runs coming down to a combiner box. A lot of work.

The 4.5P was a joke 🙂  [ Edit: and I did write 4.5S, sigh. Edited. ]

A suitable MOSFET with an adjustable voltage divider to the gate, and a LARGE heat-sink, could possibly do it. It could clamp the open circuit voltage, drawing just enough current to maintain the gate threshold voltage. With some luck, the MOSFET would not have to dissipate much power for long, though when you have no room in the battery or loads to use up excess solar power, that's when it would get very hot. In fact, it would possibly be impractical, having to dissipate some 10% of the power of the panels (at a wild guess).

Edited August 30, 20214 yr by Coulomb

9 hours ago, Coulomb said:

The best answer would be to rewire as 2S4P, making a panel redundant, or 2S5P, adding another panel of very close to the same characteristics (especially Vmp and preferably also Voc). You would need multiple cable runs coming down to a combiner box. A lot of work.

Indeed! And my panels are installed in 3 physically separate 3S arrays. The junction box is up in the attic. Imagine the trouble!

I think of an indirect but costly solution: I add a fourth battery pack of 4.8kWh (100Ah). The effect would be that the batteries would take longer to recharge until late afternoon. Then the sun has already less power, producing less OCV. And if the panels are anyway cut out until next morning I have plenty of energy stored to go trough the night. Other benefits besides the higher storage capacity would be the lesser stresses to the batteries as the currents are shared between them, hopefully extending their life time. Also the kettle effect would be attenuated.

3 hours ago, Beat said:

I think of an indirect but costly solution:

Agreed.

Another possibility that could be a lot cheaper is to use a separate MPPT for that array, one that is happy to go to 150 V or so. Just leave that Axpert MPPT unconnected. That separate MPPT just charges the battery. Make sure it has a float stage, so that as loads cause the battery voltage to sag, the MPPT will top up the battery again. Often the battery won't discharge much at all, unless a big load and big cloud coincide, and that discharge would have happened anyway even with the Axpert MPPT.

23 hours ago, Coulomb said:

Agreed.

Another possibility that could be a lot cheaper is to use a separate MPPT for that array, one that is happy to go to 150 V or so. Just leave that Axpert MPPT unconnected. That separate MPPT just charges the battery. Make sure it has a float stage, so that as loads cause the battery voltage to sag, the MPPT will top up the battery again. Often the battery won't discharge much at all, unless a big load and big cloud coincide, and that discharge would have happened anyway even with the Axpert MPPT.

I thought of that too but then dismissed it. First the investment would not increase performance of the system. Second I would loose the monitoring feature I have with Axpert and WatchPower. Who knows what monitoring feature such MPPT would have if any at all, that most likely would require an extra communication line and monitoring device.

Monitoring is important to me as I'm new in this field and learning the behavior of batteries, inverter and PV panels.

My bet payed off. With the additional battery pack it behaves much better. If battery full happens late afternoon it correctly acts floating. If earlier then it might cut out the PV panels. I found a trick to turn them on again: With the help of WatchPower adjusting one of the settings of floating voltage or bulk charge voltage even only by 0.1V the system restarts settings and reconnects the PV panels.

Another trick I found out: The instructions say to turn on a parallel system you must turn on all inverters simultaneously, then the master will be determined arbitrarily. Well that's arbitrarily to the sequence of hitting the buttons. If you want a specific inverter to become the master, turn it on a fraction of second before the other(s).

The two MKS 5K inverter performed well in parallel - until yesterday. When turning on a heavy load (3kW) the whole system shut down. I tried several times but it did it consistently. Analyzing the problem I found "Error 72" on the display. This means "Current sharing problem". Since nothing had happened to the cables I concluded that one of the parallel boards must be faulty. Luckily I had one such in spare. Today I exchanged it on the new unit. Bingo - it works again. The supplier will have to replace it to me since the units are still on warranty.

The installed 3-pole AC disconnect switches on each unit proved to be very useful. I could work on the one unit fully dead from all sources while the other unit continued working full.

 

On 2021/06/16 at 8:49 AM, rege said:

i have same problem, two axperts in parallel . after powering off and on error gone, but axpert still beeps ....

 

beeping is with or without ICC conected. 

Hi

I have recently encountered the same F80 problem on 2 Voltronic King II inverters in parallel after adding solar panels and solar charging,  see here -> https://powerforum.co.za/topic/16741-axpert-king-ii-firmware-update/?do=findComment&comment=173843

Anyone know what causes this problem yet ?

Error 80 on Two 5048MG / Axpert MKS II in Parallel – Looking for a Real Technical Solution

Hello everyone,

I am looking for feedback from users who have operated two or more Voltronic-based inverters in parallel, especially:

• MPP Solar 5048MG

• Voltronic Axpert MKS II

• Rebranded Axpert MKS II derivatives

For clarification, the 5048MG is essentially the same hardware platform as the Voltronic Axpert MKS II sold under different brand names in various countries.

My installation

• 2 × 5048MG inverters in parallel (single phase)

• Firmware 71.20 on both units

• Serial numbers:

  • 92931807100005

  • 92931807100027

• Parallel board installed

• Parallel communication cable installed

• Current sharing cable installed

• Identical battery cable lengths

• Identical AC wiring

• Common battery bank

• Same settings on both units

• Installation performed according to the official Voltronic / MPP Solar parallel installation guide

The system generally works very well and can operate for days without any issue.

The problem

I occasionally receive Fault 80.

According to the official parallel installation guide, Fault 80 is simply described as:

"CAN data loss"

Unfortunately, the official documentation provides almost no technical explanation beyond:

• check cables

• restart inverter

That is obviously not a serious root-cause analysis.

What I have already checked

• Parallel communication cables

• Current sharing cables

• Battery cable lengths

• AC wiring symmetry

• Load balancing between inverters

• Firmware consistency

• Battery bank sharing

Everything appears compliant with the installation guide.

What is frustrating

I am clearly not the only one experiencing this problem.

A large number of users on forums report intermittent Error 80 on 5048MG / Axpert MKS II systems operating in parallel.

The fault is often:

• intermittent

• difficult to reproduce

• absent for hours or days

• triggered during transitions or heavier loads

MPP Solar response

I contacted MPP Solar support.

Their response was essentially:

The product is obsolete. Continue using it until it fails and then replace it with a newer model.

Frankly, I find this answer disappointing.

These inverters are still fully operational and continue to be widely used worldwide.

I am not looking to replace two perfectly functional inverters because of a sporadic communication fault.

I would much rather understand the actual cause and solve it properly.

Questions for experienced users

1. Have you experienced Error 80 on 5048MG or Axpert MKS II units operating in parallel?

2. Were you able to identify the root cause?

3. Did replacing the parallel communication cable help?

4. Did replacing the current sharing cable help?

5. Did shielding the communication cables help?

6. Did grounding modifications help?

7. Did you find a firmware version that improved stability?

8. Is Error 80 really related to CAN communication, or is it sometimes a symptom of another synchronization issue?

9. Has anyone obtained a genuine technical explanation from Voltronic or MPP Solar?

10. Did anyone completely eliminate Error 80, and if so, how?

Additional observations

I have occasionally observed:

• transient load sharing asymmetry

• differences in PV production between the two inverters

• occasional synchronization disturbances

• rare communication-related warnings

However, the system may also run perfectly for days before Error 80 suddenly appears.

This makes me suspect that the issue may be related to:

• parallel communication timing

• current sharing synchronization

• CAN communication robustness

• firmware behavior

• or a combination of several factors

Any technical information, oscilloscope captures, firmware notes, engineering explanations, service manuals, or real-world experience would be greatly appreciated.

Thank you very much for your help.

It could be that the capacitor modification is required, or if present, the capacitor may have lost value due to transients blowing some of the "fuses" that are often inside this type of capacitor. Models with the high PV voltage (450 V or 500 V) seem to be susceptible to this. High dV/dt on the PV wires seems to induce glitches into various communications lines, including the CAN bus connections from master to slave. The OP mentioned the problem being worse around midday, when presumably PV activity is greatest.

Redressing some of the cables may also help (see link in the below).

Edited May 30May 30 by Coulomb

Dear Coulomb,

First of all, please accept my apologies for the delayed reply. Unfortunately, I did not receive any email notification of your response and only discovered it today while reviewing the forum thread.

Thank you very much for your comments. Your explanation regarding the high dV/dt generated by the high-voltage PV strings is extremely interesting and may explain several observations I have made on my installation.

My system consists of two PIP-5048MG / Axpert MKS II units operating in parallel. I have occasionally experienced Error 80 ("CAN data loss"), sometimes during periods of high PV activity, but also on a few occasions under lower solar production conditions.

I was particularly interested by your mention of the capacitor modification. I have since located the Voltronic SOP describing the installation of capacitor 31-013730-00G directly across the PV input terminals.

I would be grateful if you could clarify a few points:

• Do you know the value and specifications of capacitor 31-013730-00G?

• Was this modification introduced as a corrective action for Error 80 specifically, or for a broader EMI/noise issue?

• Have you personally seen Error 80 disappear or significantly improve after this capacitor modification?

• Is the issue mainly caused by conducted noise on the PV wiring, radiated EMI, or both?

• Do you know whether later firmware versions (71.82, 71.86, 71.92) contain any improvements related to parallel communications or Error 80?

You also mentioned cable routing improvements. Unfortunately, the link referenced in your post is no longer visible to me. Would it be possible to provide the link again or briefly describe the recommended cable arrangement?

Thank you again for sharing your experience and technical knowledge. It is greatly appreciated by those of us who continue to operate these otherwise excellent inverters.

Kind regards,

Eric Giacomini
France

Dear Coulomb,

Thank you again for your reply and for taking the time to share your experience.

First of all, please accept my apologies for the delayed response. Unfortunately, I did not receive any email notification from the forum and only discovered your message recently while reviewing the thread.

Your comments regarding high dV/dt on high-voltage PV systems were extremely interesting and may explain several observations I have made on my installation.

My system consists of:

• 2 × PIP-5048MG / Axpert MKS II operating in parallel

• 450 V MPPT versions

• Parallel communication board installed

• Current sharing cable installed

• Common lithium battery bank

The firmware currently installed on both units is:

• Main firmware (U1): 71.20

I am still trying to retrieve the exact U2 (display/MCU) and DSP firmware versions and will provide them as soon as I have them.

I have recently located a copy of firmware version 71.86 which appears to be intended specifically for the PIP-5048MG / Axpert MKS II platform.

However, I am hesitant to perform a firmware upgrade because the system is generally operating well and I am concerned about the possibility of a failed update or an unexpected regression. I have not been able to locate a copy of the currently installed 71.20 firmware and therefore I am unsure whether I would be able to revert to the existing version if problems arise.

In your opinion:

• Would you recommend upgrading from 71.20 to 71.86?

• Have you seen any evidence that later firmware versions improve Error 80 occurrences, parallel communication reliability, or overall stability of parallel systems?

• Is there any significant risk associated with moving from such an early firmware version to 71.86?

Regarding the capacitor modification you mentioned, I managed to find the Voltronic SOP describing the installation of capacitor reference:

31-013730-00G

directly across the PV input terminals.

Unfortunately, I have not been able to locate this component for sale, nor have I found any technical specifications associated with that reference.

Could you please advise:

• the capacitance value;

• voltage rating;

• capacitor technology (polypropylene film, MKP, etc.);

• whether the modification was introduced specifically to mitigate Error 80 or more generally to reduce EMI and communication disturbances;

• what specifications should be used if the original Voltronic component is no longer available.

Your explanation regarding high dV/dt on the PV wiring causing communication glitches is particularly interesting because it seems consistent with the behaviour observed on my installation. Although Error 80 sometimes occurs during periods of high solar activity, I have also observed a few occurrences during lower PV production conditions, which makes me wonder whether the capacitor modification improves overall communication robustness rather than addressing a single operating condition.

As a side note, I have developed a Python-based supervisory system called "Energy Brain" for my installation.

The goal was not to replace the inverter firmware but rather to provide higher-level energy management, battery supervision, load control, historical logging and system monitoring while leaving the inverter hardware unchanged.

The system is now operating reliably and has significantly improved the behaviour of my installation. Once the project is properly documented and cleaned up, I intend to make it available to the community so that other PIP-5048MG / Axpert users can benefit from it and contribute improvements.

Thank you again for all your work and for the knowledge you continue to share with the Axpert community.

Kind regards,

Eric Giacomini
France

4 hours ago, brunodu31 said:

I am still trying to retrieve the exact U2 (display/MCU) firmware version

My understanding is that MKS IIs drive the display directly from the main DSP chip; therefore there is no U2 firmware version.

4 hours ago, brunodu31 said:

Could you please advise:

• the capacitance value;

• voltage rating;

• capacitor technology (polypropylene film, MKP, etc.);

My file post suggests a "2.2μF 600 VDC X2 class polyester film capacitor".

4 hours ago, brunodu31 said:

Would it be possible to provide the link again or briefly describe the recommended cable arrangement?

https://powerforum.co.za/topic/15724-axpert-mks-iv-5600-corrupted-display/?do=findComment&comment=173515

This is the crux of it:

4 hours ago, brunodu31 said:

I have recently located a copy of firmware version 71.86 which appears to be intended specifically for the PIP-5048MG / Axpert MKS II platform.

However, I am hesitant to perform a firmware upgrade because the system is generally operating well and I am concerned about the possibility of a failed update or an unexpected regression. I have not been able to locate a copy of the currently installed 71.20 firmware and therefore I am unsure whether I would be able to revert to the existing version if problems arise.

In your opinion:

• Would you recommend upgrading from 71.20 to 71.86?

Unfortunately, 71.xx is a number range shared by several different models, including the PIP-5048 MGX. This version has a removable display, and is sometimes known as an Axpert MKS III, but is possibly mainly or only used in the MPPSolar model.

So it's hard to say. It should be safe I think, but the nearest firmware version I have to 71.20 is 71.17, for the MGX. Does your model have a removable display?

4 hours ago, brunodu31 said:

1. Have you seen any evidence that later firmware versions improve Error 80 occurrences, parallel communication reliability, or overall stability of parallel systems?

2. Is there any significant risk associated with moving from such an early firmware version to 71.86?

1: I don't believe that any firmwares have "hardening" against fault code 80. The firmware relies on the hardware to deliver uncorrupted messages.

2: Again, hard to say, since I don't have a copy of 71.20. I suggest that you try dressing the cables and adding the capacitor first. Please be careful with high voltage DC and largish capacitors; these can store lethal energy for many hours if there is no bleed path.

Dear Coulomb,

Thank you very much for your detailed reply and for all the information you have shared.

Your comments have been extremely helpful. We already suspected that Error 80 might be related to an EMI issue rather than a firmware issue, and the information you provided, together with the Voltronic SOPs regarding the MPPT choke wire arrangement and the PV capacitor modification, strongly reinforces that hypothesis.

My units do not have a removable display. They are 2018 PIP-5048MG / Axpert MKS II units with the 450 V MPPT input and fixed display.

Following your advice, I will first implement the hardware modifications before considering any firmware upgrade:

rearranging and twisting the MPPT choke wires according to the Voltronic SOP;

adding a 2.2 µF / 1200 VDC polypropylene power film capacitor across the PV input terminals of each inverter.

I have already ordered the capacitor and will report back with the results once the modifications have been tested.

After carefully studying the MPPT wire arrangement SOP, I noticed that Voltronic not only reroutes the wires but also keeps them closely coupled and away from nearby electronics. This seems very consistent with an EMI-related mechanism.

I would appreciate your opinion on one additional idea.

Do you think there would be any benefit in placing the MPPT choke wires inside a grounded metallic braid or metallic shield connected to protective earth at one end only?

My reasoning is that if the issue is caused by high dV/dt on these conductors, a grounded shield could further reduce radiated electric field coupling into the nearby communication and control circuitry.

Or do you believe that the capacitor modification and the revised wire routing already address the root cause sufficiently?

Thank you again for your help and for sharing your experience with the Axpert platform. Your guidance is greatly appreciated.

Kind regards,

Eric Giacomini France

7 hours ago, brunodu31 said:

Do you think there would be any benefit in placing the MPPT choke wires inside a grounded metallic braid or metallic shield connected to protective earth at one end only?

This is on the edge of my knowledge, so treat accordingly.

I'm uneasy about it. The replacement for the choke wires would obviously have to be quite high voltage rated; audio cables would break down quickly with catastrophic results.

With respect to protective earth, one end of the inductor has a high dV/dt 50 Hz square wave of amplitude equal to bus voltage plus the PV voltage. The other end has that plus a ≈20 kHz square wave also with bus voltage amplitude. The capacitance from wire to braid will be low, but with all this dV/dt, the current will be significant. I worry that this current could increase losses in the two converters (the 50 Hz DC<->AC converter and the MPPT boost converter) such that they could fail under some conditions.

Edited June 5Jun 5 by Coulomb

Thank you, that makes sense. I should clarify that I may not have explained my idea very well.

I was not considering replacing the existing PV/choke wires with shielded cable.

My idea was to keep the existing insulated wires unchanged and, if necessary, add a loosely fitting metallic braid around them as an external shield. The braid would be significantly larger than the cable bundle and separated from the conductors by the existing insulation (and possibly an additional insulating sleeve), in order to keep the capacitance as low as reasonably possible.

However, your point about the additional capacitance and the resulting HF currents is very clear. I understand that even a relatively small capacitance may introduce unwanted losses or additional stress in the converters.

For now, I will not attempt any shielding modification. I will start with the safer and documented approach:

• adding the PV input capacitor as described in the Voltronic SOP;

• keeping PV+ and PV− close together / lightly twisted where possible;

• improving cable routing away from communication wiring.

I will report back after testing.

Thank you again for your help.

One more question: do you happen to know whether any service schematics, partial schematics, or block diagrams exist for the PIP-5048MG / Axpert MKS II platform?

I am particularly interested in understanding:

• how the parallel communication board is connected internally;

• whether “CAN data loss” really refers to a physical CAN bus or to a proprietary internal communication channel;

• where the communication transceivers are located;

• how the communication board is powered and referenced;

• how close the MPPT choke wiring is to the communication circuitry;

• whether Voltronic ever documented the capacitor / wire-routing modification in relation to communication faults such as Error 80.

Even a partial schematic of the communication board, parallel board, or MPPT input area would be extremely useful.

I fully understand that complete schematics may not be publicly available, but any archived service information, block diagrams, or practical experience would help a lot.

Thank you again.

I found the official Voltronic service manual for the 5048MG platform (2018 version).

Interestingly, it confirms the presence of a common-mode choke directly on the PV input, before the MPPT stage. This gives much more credibility to the later Voltronic SOP recommending the addition of a 2.2 µF film capacitor across PV+ and PV−, as it effectively completes the EMI input filter rather than acting as a simple bulk capacitor.

It also shows how close the MPPT wiring, control board and communication boards are inside the unit, which may be relevant when investigating communication-related faults such as Error 80.

I thought this document could be useful to others working on these inverters.

AXPERT MKS II 5KW 230V Service manual 201807A-compressé.pdf

2 hours ago, brunodu31 said:

Even a partial schematic of the communication board, parallel board, or MPPT input area would be extremely useful.

There is a collection of some partial schematic traces here, including some of the paralleling boards.

I came across this post, where a PIP-5048 owner fixed a fault code 80 issue by replacing paralleling boards.

Dear all

After studying the service manual, the internal board layout, the Voltronic SOP, and several teardown pictures, we have developed a working hypothesis regarding the intermittent Error 80 observed on some parallel Axpert/Voltronic 5048MG units.

The original Voltronic SOP only addresses LCD flickering by repositioning the MPPT choke wires. However, after a closer analysis of the inverter architecture, we believe the root cause may be broader than the LCD issue.

The MPPT choke is physically mounted far away from the MPPT power board. The two wires connecting the choke to the MPPT board (P2/P3) are relatively long and appear to be part of the MPPT switching current loop. These wires carry high current and high dV/dt switching waveforms generated by the MPPT IGBTs/MOSFETs operating at approximately 50 kHz.

While the toroidal choke itself should radiate very little magnetic field, the long connecting wires form a large switching loop that is likely to generate both conducted and radiated EMI. Inspection of the inverter shows that these wires run very close to several ribbon cables and communication boards, including boards associated with the parallel system (PAR-P board, PAR communication board, communication board and main board).

Our hypothesis is that the switching loop radiates broadband EMI which couples into the nearby ribbon cables and communication circuits. The fundamental switching frequency is only around 50 kHz, but the fast switching edges generate harmonics extending into the MHz range. This may occasionally corrupt communication between the parallel control boards, resulting in Error 80.

To investigate this theory, we will first implement the official Voltronic capacitor modification (2.2 µF film capacitor across PV+ and PV−), which should improve differential-mode filtering on the PV input.

If the problem persists, we plan to shield the two MPPT choke wires. The proposed design is intended to minimize additional capacitance:

• each MPPT wire will be routed inside its own PVC insulating tube;

• the two tubes will be placed side by side;

• a copper braided shield will surround both tubes;

• an outer heat-shrink sleeve will provide mechanical protection;

• the shield will be connected to chassis earth at one end only;

• significant air spacing will remain between the conductors and the shield in order to keep conductor-to-shield capacitance as low as possible (estimated only a few tens of pF).

The objective is not to filter the MPPT current itself, but to contain the radiated electric field generated by the switching loop and prevent coupling into the nearby communication and parallel-control circuitry.

At this stage this remains a hypothesis, but it is consistent with:

• the physical layout of the inverter;

• the location of the MPPT choke wiring;

• the proximity of the communication ribbon cables;

• the Voltronic LCD flicker correction;

• and the intermittent nature of Error 80.