Hi.

I have an installation about 30 months old that has been running fine. Axpert IV 5600w 48v connected to 6 Pylontech US3000 batteries. All has been working fine until a few days ago when I found a string smell of hot electrics. Since then when charging from solar the inverter repeatedly flashes red and closes down (no error code) it then restarts a few seconds later then closes again on and on.

No fault codes and no further smells of hot electrics.

All cooling fans are working well, filters are clean and there are no obstructions in the heat sinks.

Any suggestions of what to check would be most appreciated.

Many thanks.

3 hours ago, Oliver in Spain said:

Hi.

I have an installation about 30 months old that has been running fine. Axpert IV 5600w 48v connected to 6 Pylontech US3000 batteries. All has been working fine until a few days ago when I found a string smell of hot electrics. Since then when charging from solar the inverter repeatedly flashes red and closes down (no error code) it then restarts a few seconds later then closes again on and on.

No fault codes and no further smells of hot electrics.

All cooling fans are working well, filters are clean and there are no obstructions in the heat sinks.

Any suggestions of what to check would be most appreciated.

Many thanks.

Without fault codes try and see if you can manually record the DC voltage as well as current to the MPPT while charging from solar when the inverter cuts out. It might just give a clue as to the reason.

This is very likely aging capacitors in the DC-DC stage. Voltronic inverters often fail this way after 2–3 years of continuous use. But lets us ask the fundi on Voltronic inverters for his assessment @Coulomb

Good morning from sunny Spain.

I think that I initially described this fault badly as the inverter does not actually shut down. To better explain I have filmed overnight and this morning to record the fault. It appears to only happen during solar charging and more often the higher the amperage. The gaps between the fault vary, sometimes several minutes others immediate. I've also noticed that error code 32 (Communication failure between inverter and display panel) does flash up.

When the gap between faults is longer input and charging do resume though not seen here as uploads are limited to 3MB.

Please any thoughts.

PS. Please ignore date and time stamp

Edited May 12, 20251 yr by Oliver in Spain

23 hours ago, Oliver in Spain said:

Since then when charging from solar the inverter repeatedly flashes red and closes down (no error code) it then restarts a few seconds later then closes again on and on.

Very strange that there is no fault code. If you have monitoring software, does it show any faults? Axperts generally write the last fault to EEPROM, which is readable with a pair of commands (QF and QFAULT; see this post for details).

15 hours ago, TaliaB said:

This is very likely aging capacitors in the DC-DC stage. Voltronic inverters often fail this way after 2–3 years of continuous use.

I find the two large bus capacitors last pretty well. It's more likely that the power supply capacitors fail, and this does cause restarting, but it's usually not specific to solar charging. Being limited to solar charging suggests something on the Solar Charge Controller board. I'm not familiar with the high PV voltage SCCs. Something near the output might drag down the bus voltage, which might cause a restart.

The other possibility is the buck transistor (usually an IGBT, could be a MOSFET), either the transistor itself or its gate drive circuit or associated power diode. This transistor is only active when charging. Oliver in Spain, can you charge from utility? That uses the same buck transistor, but not the SCC (solar charger).

Is the fault indeed confined to solar charging? I.e. if you disable solar charging, does the inverter operate normally, e.g. battery to load if AC-in is removed?

Does it always show a wildly wrong voltage for the AC output voltage? Bad measurement errors suggest a fault with the -12 V power supply.

If the inverter restarts even when not solar charging, that does look like bad power supply capacitors. See this post if you are able to repair it yourself.

If it's always showing a wildly wrong AC out voltage measurement, I suggest not running it with sensitive loads or for long periods of time.

19 minutes ago, Coulomb said:

Is the fault indeed confined to solar charging? I.e. if you disable solar charging, does the inverter operate normally, e.g. battery to load if AC-in is removed?

Does it always show a wildly wrong voltage for the AC output voltage? Bad measurement errors suggest a fault with the -12 V power supply.

If the inverter restarts even when not solar charging, that does look like bad power supply capacitors. See this post if you are able to repair it yourself.

If it's always showing a wildly wrong AC out voltage measurement, I suggest not running it with sensitive loads or for long periods of time.

Hi. Thanks for getting back.

AC is on a time switch as I get free electricity in the evenings which I use to top up the batteries if needed (SUB setting). The inverter otherwise operates normally until the the sun comes up and works fine with the panels disconnected.

If I run the inverter in user defined battery (programmer 5) and drop down the combined charging to 30A then the inverter operates normally. 30A is fine for summer but will be too slow for many winter days.

I did open her up to check the fans and heat sinks and while there had a look for any obviously burned components but didn't see and.

Once again many thankss

20 hours ago, Oliver in Spain said:

I did open her up to check the fans and heat sinks and while there had a look for any obviously burned components but didn't see any.

Great! Did you look along the side of the heatsinks? One of the "usual suspects" are the MOSFETs, and they happen to be right against the edge of the case where you may not notice them with a casual glance. Sometimes looking in the side with a torch, even with the lid still on, can reveal broken epoxy, legs blown off, etc. But also the larger transistors on the middle heatsink; they can be hidden under a lip of heatsink fins too.

Also, use your nose; burned epoxy has a distinct smell. I'll sometimes use a straw or similar as a sort of nasal stethoscope, to direct my "smell focus".

20 hours ago, Oliver in Spain said:

30A is fine for summer but will be too slow for many winter days.

So 30 A won't trigger it, but higher current limits will?

So the problem with battery type PYL or whatever you normally use is that the BMS will usually set a limit higher than 30  A?

That's a bit unusual. I'll let it rattle around in my head for a while.

2 hours ago, Coulomb said:

Great! Did you look along the side of the heatsinks? One of the "usual suspects" are the MOSFETs, and they happen to be right against the edge of the case where you may not notice them with a casual glance. Sometimes looking in the side with a torch, even with the lid still on, can reveal broken epoxy, legs blown off, etc. But also the larger transistors on the middle heatsink; they can be hidden under a lip of heatsink fins too.

Also, use your nose; burned epoxy has a distinct smell. I'll sometimes use a straw or similar as a sort of nasal stethoscope, to direct my "smell focus".

So 30 A won't trigger it, but higher current limits will?

So the problem with battery type PYL or whatever you normally use is that the BMS will usually set a limit higher than 30  A?

That's a bit unusual. I'll let it rattle around in my head for a while.

Great advice! I will strip her down again tomorrow.

For some reason at lower powers the inverter triggers less often though I still have to keep an eye on her.

Yes, for PYL it automatically selects 80A so selecting USE is the only workaround but then, obviously, there is no communication between batteries and inverter which is not ideal

Fingers crossed for tomorrow

Sorry been 2 days now but yesterday was kind of busy.

Anyway I stripped her down again and tried using both visual and your sniffascope to locate the problem but with no result. I decided not to go any further for the time being until I can fit a reserve inverter and the strip the Axpert IV.

On the same topic but in a different vein do you happen to know how I can find the IMP for the Axpert IV 5.6Kw. This parameter is not given in any of the documentation nor can I find it online. Failing that is there anyway to calculate the IMP using other parameters?

Any advice much appreciated-

Edited May 15, 20251 yr by Oliver in Spain

On 2025/05/15 at 9:51 PM, Oliver in Spain said:

how I can find the IMP for the Axpert IV 5.6Kw.

Err, Imp (maximum power point current) is a parameter of panels, not inverters.

If you mean what is the panel current limit for that inverter, that makes more sense. Usually it's in the manual under Specifications, then Charging. If not, tell me if it's a VM IV or an MKS IV and I might be able to find the limit from the firmware.

Hi.

Many thanks, yes it is in the manual - a friend who knows much more about these things than me was asking for the IMP.