kuba.cz

Some more schematics here. These are from Easun SMW 8kW which is, I believe, identical to Axpert Max 8kW. In this case the control board did have part references printed so most of those in the schematic should be correct. It's a multilayer board but only power planes are on the inside layers so it's not that hard to trace. The main difference, compared to Anern, is that this board uses multiplexers for 8 of the ADC's inputs, increasing total number of available analog inputs to 24.
I also made a schematic of the SCR board and some fragments of the main board.
I'm not going to make schematics of any power supplies as these are already pretty obvious. Just note that the topology in this case is different from Anern's. There's no intermediate SPS_IN (150V+) branch. The main power supply and bus softstart are located on the main board and powered directly by the battery voltage through a diode. The grid/AC power supply and solar power supply are on a separate board, both of these output around 63-66V and also provide power to the main power supply through diodes. Unlike Anern's, this topology does not need a relay in the softstart circuit.
I made a note of some critical parts (MOSFET type, shunt resistor value and how they deal with voltage spikes):
main SPS: JCS86N25WT, 0.15R, RC snubber 2x47R (parallel), 2.2nF
softstart: SIF13N50C, 0.62R, RC snubber 2x22R (parallel), 220pF
grid SPS: SVF9N90F, 0.47R, RCD clamp 15k/5W, 10nF
solar SPS: SVF9N90F, 0.47R, RCD clamp 15k/5W, 10nF
Original KiCad files and PDF schematics are available on my GitHub: https://github.com/solar-pwr/axpert/
There will be errors as usual, so every feedback is appreciated.

Here are some schematics that I reverse engineered from Anern Victor Max 10.2kW inverter. Should be very similar to Axpert VM models. Of course, part references and connector pinouts are different. Also ADC and GPIO assignments do not match genuine Voltronic's.
The SCC board schematic is complete - PV boost circuit, voltage and current measurement, AC power supply and bus soft start circuit.
Then there's a schematic of the two power supplies on the main board - this inverter uses an auxillary 150V power supply to start from the battery.
Also a I attempted to trace the analog part of the control/DSP board. This was little bit harder as there were no printed part references on the board. But all op-amps are there, nothing important (for understanding the circuit function) should be missing. [15/Aug/2025 added the remaining "digital" part]
I think there will be some errors, so every feedback is appreciated. I can provide KiCad project files if anyone is interested.

Not yet. I'm still at the very beginning of drawing part 2/2, hopefully I'll be able to finish it later this year. But I do have the board on hand so I can provide some part values/pinouts if needed.

Here are some photos. Not great but I tried my best.
To avoid confusion, I have to note that I've made some modifications on the main board. I have three of these boards (got them as not-working) and all of them had signs of arcing around the drain of Q71 or TX9's primary winding. On this particular one, U10 and R255 was faulty. There were some unsuccessul repair attempts from the previous owner.
After replacing the parts (including Q71 which still measured OK), I decided to also remove R249/D64 and install the unpopulated RCD clamp to reduce the voltage spikes. Used 3.3nF capacitor for C143, 150k/3W resistor for R245 and some diode that I don't remember. That didn't work out, the same parts blew again after a few power ons (exactly when the soft start turned off and SPS_IN raised to the bus voltage). BUT most likely due to my mistake that I didn't check R253 which was already open-circuit. Wrongly suspecting the RCD clamp's diode to be too slow, I deciced to try an RC snubber instead, consisting of a 100pF/3kV MLCC capacitor and 33R/5W resistor, connected between source and drain of Q71. Only then, watching the waveforms on the oscilloscope, I realized that the duty cycle is constant 50% and the power supply keeps switching off and on by the optocoupler feedback. That lead me to the R253 1k resistor. After replacing it, everything works fine and the waveform on the drain of Q71 looks nice so I left the RC snubber there, not trying to revert to the RCD clamp. So that's the current state of the main board on the photo.
Also I swapped the DSP, the orignal one was TMS320F28062PZT, this one is TMS320F28066PZT (differs in memory size), but this is only related to my experiments, not a malfunction of the inverter.

Some more schematics here. These are from Easun SMW 8kW which is, I believe, identical to Axpert Max 8kW. In this case the control board did have part references printed so most of those in the schematic should be correct. It's a multilayer board but only power planes are on the inside layers so it's not that hard to trace. The main difference, compared to Anern, is that this board uses multiplexers for 8 of the ADC's inputs, increasing total number of available analog inputs to 24.
I also made a schematic of the SCR board and some fragments of the main board.
I'm not going to make schematics of any power supplies as these are already pretty obvious. Just note that the topology in this case is different from Anern's. There's no intermediate SPS_IN (150V+) branch. The main power supply and bus softstart are located on the main board and powered directly by the battery voltage through a diode. The grid/AC power supply and solar power supply are on a separate board, both of these output around 63-66V and also provide power to the main power supply through diodes. Unlike Anern's, this topology does not need a relay in the softstart circuit.
I made a note of some critical parts (MOSFET type, shunt resistor value and how they deal with voltage spikes):
main SPS: JCS86N25WT, 0.15R, RC snubber 2x47R (parallel), 2.2nF
softstart: SIF13N50C, 0.62R, RC snubber 2x22R (parallel), 220pF
grid SPS: SVF9N90F, 0.47R, RCD clamp 15k/5W, 10nF
solar SPS: SVF9N90F, 0.47R, RCD clamp 15k/5W, 10nF
Original KiCad files and PDF schematics are available on my GitHub: https://github.com/solar-pwr/axpert/
There will be errors as usual, so every feedback is appreciated.

Here are some schematics that I reverse engineered from Anern Victor Max 10.2kW inverter. Should be very similar to Axpert VM models. Of course, part references and connector pinouts are different. Also ADC and GPIO assignments do not match genuine Voltronic's.
The SCC board schematic is complete - PV boost circuit, voltage and current measurement, AC power supply and bus soft start circuit.
Then there's a schematic of the two power supplies on the main board - this inverter uses an auxillary 150V power supply to start from the battery.
Also a I attempted to trace the analog part of the control/DSP board. This was little bit harder as there were no printed part references on the board. But all op-amps are there, nothing important (for understanding the circuit function) should be missing. [15/Aug/2025 added the remaining "digital" part]
I think there will be some errors, so every feedback is appreciated. I can provide KiCad project files if anyone is interested.

Some more schematics here. These are from Easun SMW 8kW which is, I believe, identical to Axpert Max 8kW. In this case the control board did have part references printed so most of those in the schematic should be correct. It's a multilayer board but only power planes are on the inside layers so it's not that hard to trace. The main difference, compared to Anern, is that this board uses multiplexers for 8 of the ADC's inputs, increasing total number of available analog inputs to 24.
I also made a schematic of the SCR board and some fragments of the main board.
I'm not going to make schematics of any power supplies as these are already pretty obvious. Just note that the topology in this case is different from Anern's. There's no intermediate SPS_IN (150V+) branch. The main power supply and bus softstart are located on the main board and powered directly by the battery voltage through a diode. The grid/AC power supply and solar power supply are on a separate board, both of these output around 63-66V and also provide power to the main power supply through diodes. Unlike Anern's, this topology does not need a relay in the softstart circuit.
I made a note of some critical parts (MOSFET type, shunt resistor value and how they deal with voltage spikes):
main SPS: JCS86N25WT, 0.15R, RC snubber 2x47R (parallel), 2.2nF
softstart: SIF13N50C, 0.62R, RC snubber 2x22R (parallel), 220pF
grid SPS: SVF9N90F, 0.47R, RCD clamp 15k/5W, 10nF
solar SPS: SVF9N90F, 0.47R, RCD clamp 15k/5W, 10nF
Original KiCad files and PDF schematics are available on my GitHub: https://github.com/solar-pwr/axpert/
There will be errors as usual, so every feedback is appreciated.

MAXE11K_TWIN_DSP_78.11(1).7z

Some more schematics here. These are from Easun SMW 8kW which is, I believe, identical to Axpert Max 8kW. In this case the control board did have part references printed so most of those in the schematic should be correct. It's a multilayer board but only power planes are on the inside layers so it's not that hard to trace. The main difference, compared to Anern, is that this board uses multiplexers for 8 of the ADC's inputs, increasing total number of available analog inputs to 24.
I also made a schematic of the SCR board and some fragments of the main board.
I'm not going to make schematics of any power supplies as these are already pretty obvious. Just note that the topology in this case is different from Anern's. There's no intermediate SPS_IN (150V+) branch. The main power supply and bus softstart are located on the main board and powered directly by the battery voltage through a diode. The grid/AC power supply and solar power supply are on a separate board, both of these output around 63-66V and also provide power to the main power supply through diodes. Unlike Anern's, this topology does not need a relay in the softstart circuit.
I made a note of some critical parts (MOSFET type, shunt resistor value and how they deal with voltage spikes):
main SPS: JCS86N25WT, 0.15R, RC snubber 2x47R (parallel), 2.2nF
softstart: SIF13N50C, 0.62R, RC snubber 2x22R (parallel), 220pF
grid SPS: SVF9N90F, 0.47R, RCD clamp 15k/5W, 10nF
solar SPS: SVF9N90F, 0.47R, RCD clamp 15k/5W, 10nF
Original KiCad files and PDF schematics are available on my GitHub: https://github.com/solar-pwr/axpert/
There will be errors as usual, so every feedback is appreciated.

Thanks for the guidance. I took a working panel, made a fimware dump using stm32cubeprog and blew the backup to the dead unit. All working fine now.
Thanks!

My MAX7.2 has suddenly exposed a failure mode and is presenting fault code F52 on the LCD display.
The internet and available documentation describe this fault as “Bus Voltage Too Low.” I have also tried to gather as much information as possible from this forum and others. However, based on what I could find, it appears to be a fairly random fault, and I could not locate any posts that led to a definitive solution.
I have not opened the machine yet, as I want to gain as much insight into the problem as possible beforehand.
So far, I have run the following functional tests, and in my case the failure is deterministic, not random at all.
Test 1
Conditions: Battery available (52.7 VDC), NO PV, NO GRID
When I switch the inverter on, it enters its diagnostic phase and then outputs 220 VAC on the load output. It also asserts a relay, most probably the load (inverter) relay. After less than one second, the 220 VAC collapses and the inverter shuts down, displaying F52 on the LCD.
Test 2
Conditions: Battery available (52.7 VDC), PV ON, NO GRID (PV available under sunny conditions)
When I switch the inverter on, it enters its diagnostic phase and outputs 220 VAC on the load output, again asserting the load relay. The output remains stable and no fault occurs.
However, the PV does not charge the battery; it only powers the AC load output. The settings that allow PV battery charging are correctly configured.
Test 3
Conditions: Battery available (52.7 VDC), PV OFF, GRID ON
When I switch the inverter on, it enters its diagnostic phase and outputs 220 VAC on the load output, asserting the load relay. The output remains stable and no fault occurs.
However, the grid does not charge the battery, even though the settings to allow grid charging are correctly configured.
Initial Assessment
Based on the above conditions and observations, the F52 fault strongly suggests that the DC-DC converter, which is responsible for converting battery voltage to the internal bus voltage (and vice versa), is not functioning.
This explains nearly all observations. The only apparent contradiction is why bus voltage exists initially (for about one second) when running in battery-only mode. After some thought, I realized that a bus soft-start circuit is present. The machine uses this low-power soft-start path to pre-charge the bus capacitors and verify bus integrity (checking for shorts, etc.). This accounts for the brief energy available to produce AC for about one second. The bus then collapses because energy is not replenished via the DC-DC converter.
I am confident that the high-side IGBTs and low-side MOSFETs of the DC-DC converter are not blown; otherwise, the soft-start process would fail. My attention is therefore focused on the SG3525 PWM generator, which may not be enabling DC-DC operation.
If the SG3525 itself is functional, then the initial transistor amplifier stages that drive the A and B phase outputs could be faulty. The ±12 V rails are another possibility, but I have largely ruled them out because these rails also power the measurement op-amps, and a fault there would significantly distort the readings.
Of course, the DSP control board could also be at fault by not enabling the SG3525 PWM, or the opto-coupler driver stage may have failed.
Another possible fault could be a failed buck IGBT, but I have tentatively ruled this out because the body diode should still allow some discharge path from the battery to the bus. I hope this assumption is correct.
At this stage, my money is on the SG3525 or its associated circuitry. I certainly hope so, as I am not in the mood to replace power silicon given the amount of mechanical work required to rework this machine’s heatsinks.
I will provide an update when I open the unit during the week, and hopefully this will help someone else in the future who has to deal with the same F52 fault.

Here are some schematics that I reverse engineered from Anern Victor Max 10.2kW inverter. Should be very similar to Axpert VM models. Of course, part references and connector pinouts are different. Also ADC and GPIO assignments do not match genuine Voltronic's.
The SCC board schematic is complete - PV boost circuit, voltage and current measurement, AC power supply and bus soft start circuit.
Then there's a schematic of the two power supplies on the main board - this inverter uses an auxillary 150V power supply to start from the battery.
Also a I attempted to trace the analog part of the control/DSP board. This was little bit harder as there were no printed part references on the board. But all op-amps are there, nothing important (for understanding the circuit function) should be missing. [15/Aug/2025 added the remaining "digital" part]
I think there will be some errors, so every feedback is appreciated. I can provide KiCad project files if anyone is interested.

@Coulomb All schematics are here https://powerforum.co.za/topic/32491-anern-102kw-schematics/ in my first post. Part 2 was added later. I've just uploaded original KiCad files to my GitHub as well: https://github.com/solar-pwr/anern .
BTW, yesterday, while working on an Easun SMH, I realized that this Anern is a rare case which can only measure charging current on the DC/DC converter's Hall sensor. The output of the op-amp is not shifted to +1.65V so discharging current will always be read as zero on the ADC.
Easun SMH does have a voltage divider between the output of the op-amp and +3.3V (taken from a voltage follower, not directly from the power rail). I think it will be similar in all MAX models.

I'm not sure what was the reason to remove the snubber, but the power supply seems to run fine without it as long as the output current stays within normal range. But when there's a short circuit (and that can be on the COM port also), the voltage spikes can be high enough to cause arcing on the transistor drain or transformer pins.
If UC3845 failed, don't forget to check R253. The power supply may run even if this resistor is open-circuit, but UC3845 will stay at 50% duty cycle, just switching on and off according to the voltage feedback. In this mode, the spikes on the primary will be extremely high.
Currently I'm running two inverters with RC snubber added between source and drain of the MOSFET without any issues (that's not an RCD clamp as show in the schematic). I used 100pF/3kV MLCC capacitor and 33R/5W resistor as already mentioned.

A good way to start may be powering the inverter through the battery terminals and watching the bus voltage (red and black wire from the SCC board). When the soft-start circuit gets enabled, it should raise to somewhere around 400V within a few seconds. If this does not happen, then the corresponding output driver (ULN2003) may be faulty. Otherwise, it can be an issue with the ADC inputs, op-amps, possibly multiplexer (if this model has one).

These are two unrelated problems. The update via COM port fails probably because of a weak/slow optocoupler or some other hardware problem which corrupts the data.
When uploading the firmware update via JTAG you get F99 which means "missing bootloader". That's expected. The firmware checks for a signature at the end of sector A where the bootloader resides. And it's not there because the firmware update does not contain the bootloader. When flashing via COM port, sector A is never erased or overwriten but the JTAG utility by default erases all sectors.
I've merged the patched firmware with part of your original file. This one should work if uploaded by JTAG. Do not use this with the original update utility.
dsp_374.04_patched_05_wboot.hex

Only low voltage (145V) models convert PV input to battery levels. On high voltage (500V) models, PV input goes to the high voltage side. Check the schematic here:
https://powerforum.co.za/topic/14666-repair-of-axpert-inverters-a-journey-started/#findComment-138439
edit: Or better this one:

The first one doesn't have a PV input, actually.

Only low voltage (145V) models convert PV input to battery levels. On high voltage (500V) models, PV input goes to the high voltage side. Check the schematic here:
https://powerforum.co.za/topic/14666-repair-of-axpert-inverters-a-journey-started/#findComment-138439
edit: Or better this one:

The first one doesn't have a PV input, actually.

Here are some schematics that I reverse engineered from Anern Victor Max 10.2kW inverter. Should be very similar to Axpert VM models. Of course, part references and connector pinouts are different. Also ADC and GPIO assignments do not match genuine Voltronic's.
The SCC board schematic is complete - PV boost circuit, voltage and current measurement, AC power supply and bus soft start circuit.
Then there's a schematic of the two power supplies on the main board - this inverter uses an auxillary 150V power supply to start from the battery.
Also a I attempted to trace the analog part of the control/DSP board. This was little bit harder as there were no printed part references on the board. But all op-amps are there, nothing important (for understanding the circuit function) should be missing. [15/Aug/2025 added the remaining "digital" part]
I think there will be some errors, so every feedback is appreciated. I can provide KiCad project files if anyone is interested.

Not exactly 175V but I can see two limits related to grid voltage in 64.xx firmwares. The first one depends on setting 03. For APL, grid is considered "lost" at 90V and recovers at 100V. For UPS it's 180V/170V.
Then there are the following limits for exporting to grid which are set depending on the country:

lower limit
upper limit
India
195.5V/200.5V
253V/248V
Germany/South America
184V/198V
264.5V/250V
These are hardcoded in the firmware and cannot be changed by any serial command. The only way to change them is to modify the firmware, which would only be possible if we had the original one for this inverter.

Not exactly 175V but I can see two limits related to grid voltage in 64.xx firmwares. The first one depends on setting 03. For APL, grid is considered "lost" at 90V and recovers at 100V. For UPS it's 180V/170V.
Then there are the following limits for exporting to grid which are set depending on the country:

lower limit
upper limit
India
195.5V/200.5V
253V/248V
Germany/South America
184V/198V
264.5V/250V
These are hardcoded in the firmware and cannot be changed by any serial command. The only way to change them is to modify the firmware, which would only be possible if we had the original one for this inverter.

Here are some schematics that I reverse engineered from Anern Victor Max 10.2kW inverter. Should be very similar to Axpert VM models. Of course, part references and connector pinouts are different. Also ADC and GPIO assignments do not match genuine Voltronic's.
The SCC board schematic is complete - PV boost circuit, voltage and current measurement, AC power supply and bus soft start circuit.
Then there's a schematic of the two power supplies on the main board - this inverter uses an auxillary 150V power supply to start from the battery.
Also a I attempted to trace the analog part of the control/DSP board. This was little bit harder as there were no printed part references on the board. But all op-amps are there, nothing important (for understanding the circuit function) should be missing. [15/Aug/2025 added the remaining "digital" part]
I think there will be some errors, so every feedback is appreciated. I can provide KiCad project files if anyone is interested.

It is possible to modify the software, the problem is that we don't know why the manufacturer put this derating condition there. In theory I can't see which part of the hardware could be the reason for this kind of limitation. But there may be parasitic effects which only become apparent when the inverter is operated above these conditions. I mean, the risk of a catastrophic failure is very high with such software modifications.

Okay, so due to high demand 😀 I'm posting it here. Hopefully it doesn't cause more harm than good. As always, make sure your battery (BMS) doesn't disconnect while charging - that seems to be the main risk here. Also I'd recommend to use at least two or three battery packs in parallel. Charging current over 100A would be a lot for a single 280Ah battery.
dsp_278.07_patched_200V_derate_460V.zip

I don't think these are interchangable. However I happen to have 373.63 modified already. Lada.cb asked me for this one about 10 days ago and reported it working correctly in this topic. Firmware file in the attachment.
Thanks in advance, I'll have a look at that.
dsp_373.63_patched_05_200V_derate_460V.zip