First, I'd like to introduce myself to this forum and I'm very grateful for the acceptance of my membership. My name is Diego, I'm from Buenos Aires, Argentina, and a few weeks ago I bought a used Asper Max II 8kW solar panel system that had never been used before, so it was practically new but out of warranty (purchased in 2021). I installed the system and everything seemed fine: two strings of four 650W panels each, five Pylontech UP5000 batteries, and the external power line.

The first error I detected was the inability to connect to the DSP via COM. I have experience with systems since I work with servers and switches that I generally manage through this method, and I was surprised that none of my adapters could connect to the equipment and read its data. I could connect to the screen and flash it repeatedly, but not to the main DSP, as if there were no communication between the U2 screen and the U1 DSP. When using the Power Energy program, it didn't detect anything, and when trying to upgrade the firmware, the screen displayed "update yes" for a few seconds and then disconnected.

The second problem was that there was no communication between the device and the Pylontech BMS. So I decided to upgrade the system. First, I updated my U1 from 54.04 to 54.06 via OTA, since, as I explained before, I couldn't flash U1 via COM or USB cable. It only allowed it from the screen menu by going to the USB option. So far, so good. I finished flashing and saw that the battery problem persisted. I kept reading and understood that I had to update the screen, which was on U2 122.22. I changed it to 22.25, and like magic, my subjects connected to the BMS.

Now things are getting ugly... After getting everything working, I saw in a post that the latest firmware for my unit was 81.08, so I decided to flash it via USB.

Goodbye unit, error 32, and I couldn't connect and flash the U1 via COM port or USB. I tried absolutely everything: I bought five adapters, I tried the cable with the 3.3k resistor, but nothing worked. The flashing program gets to the screen but doesn't advance to the main controller. I'd been waiting for the forum to accept my post for several days so I could share my experience, and just this morning I drove 250km each way to the official Voltronic distributor in Argentina to deliver my unit. Like a joke, I got home a few hours ago and saw the forum had accepted my post :)

Now I'm waiting to hear what the technical support people tell me. I didn't try to open it or tamper with the security stickers, even though it's no longer under warranty, but I'm betting there's a missing physical connection between the display and the motherboard. That's the only explanation I can think of. Sorry for the long message, but I'm using it as a way to vent. A big hello to the whole community!

For good monitoring software that typically works with Voltronic / Axpert inverters as well as pylontech, one can look at http://www.multisibcontrol.net/ . one then sets the inverter battery settings to user with recommended charge / discharge / float values etc.

There are also several articles on the forum to make up the USB - Serial cable for the UP2000 and UP5000 series pylontech cables. One can also use RS485 but with multisib it can only report on a limited number of battery's (8?10? via rs485 I think?) where as with the up5000 you can have up to 16, and on serial it can detect all of them. Or multisib can also do two packs of 16 if UP5000's, via serial or (8? 10? ) on rs485. Serial is preferred for the battery's as it can see all of them. CANBUS will only work with an inverter if the inverter knows how to read the received data.

On the topic of firmware for the voltronics, one has to be very careful :) You really have to be sure that you have the correct firmware(s), as from what I have seen they can have multiple firmwares for the inverter, in other words one part for the display, and another for the main board all in one update package, and you have to be sure of what display / mainboard you have etc. search the forum for it and you may get some ideas.

However it maybe best to get your supplier involved. As it's somewhat easy to potentially BRICK the inverter, when trying to upgrade versions that are not compatible. Chipsets seem to play a big part here.

You could add specifics of the inverter as per the "boiler plate" to the post for the inverter, batteries, panels details voc etc? Photos maybe with the details, it may assist anyone else who can give suggestions on what to look for. You can blank out serial details.

On 2025/12/02 at 5:31 AM, Dieguirri said:

First, I updated my U1 from 54.04 to 54.06 via OTA...

This means that you have an inverter with a '2809 DSP chip.

On 2025/12/02 at 5:31 AM, Dieguirri said:

Now things are getting ugly... After getting everything working, I saw in a post that the latest firmware for my unit was 81.08,

Unfortunately, 81.xx firmwares are only for inverters with the '28066 DSP chip. The 81.xx firmwares will call a calibrate function in the firmware very early on, in the first few milliseconds of operation. Unfortunately, the '2809 is an older chip, which does not have ROM memory at the address that the firmware calls. The result is that the DSP crashes.

The only hope is to load a 54.xx Max II firmware (54.06 is still the latest available for your model) and start the upload at just the right instant so that the bootloader detects the start of the reflash before it runs the main firmware. See the If you Think Your Inverter is Bricked for clues on how to do this. Or use a JTAG device to flash the firmware, but that has its own issues as the firmware is password protected. Or buy a new control board for your inverter, but the hassle is getting the exact right card with suitable firmware on it, when there are so many variants that look nearly the same. If you buy it from whoever sold you the inverter, they should get the exact model number from you and hopefully supply the right card.

I try to make this difference clear in my firmware posts, but I get that the whole thing gets confusing. Voltronic don't help themselves much with this; they could do a simple test before calling the calibrate function. Sorry for your difficulty, and I hope you can get it resolved soon.

8 hours ago, Coulomb said:

Esto significa que tienes un inversor con un chip DSP '2809.

Lamentablemente, los firmwares 81.xx solo son para inversores con el chip DSP '28066. Estos firmwares activarán una función de calibración en el firmware muy pronto, en los primeros milisegundos de funcionamiento. Lamentablemente, el '2809 es un chip más antiguo, que no tiene memoria ROM en la dirección a la que llama el firmware. Como resultado, el DSP falla.

La única esperanza es cargar el firmware 54.xx del Max II (54.06 sigue siendo la última versión disponible para tu modelo) e iniciar la carga en el momento justo para que el gestor de arranque detecte el inicio de la actualización antes de ejecutar el firmware principal. Consulta " Si crees que tu inversor está bloqueado" para obtener pistas sobre cómo hacerlo. También puedes usar un dispositivo JTAG para actualizar el firmware, pero esto conlleva sus propios problemas, ya que está protegido por contraseña. También puedes comprar una nueva placa de control para tu inversor, pero el problema reside en conseguir la tarjeta exacta con el firmware adecuado, cuando hay tantas variantes que parecen casi iguales. Si se lo compras a quien te vendió el inversor, debería obtener el número de modelo exacto y, con suerte, proporcionarte la tarjeta correcta.

Intento aclarar esta diferencia en mis publicaciones sobre el firmware, pero entiendo que todo se vuelve confuso. Voltronic no se ayuda mucho con esto; podrían hacer una prueba sencilla antes de llamar a la función de calibración. Disculpa la dificultad y espero que puedas resolverla pronto.

Thanks for your reply, that's what I thought. Anyway, I already took it to the Voltronic service center in my country. My remaining question is why I was never able to connect to the chip via COM when the inverter was working. I could connect to the display, but that was it.

My remaining question is why I was never able to connect to the chip via COM when the inverter was working. I could connect to the display, but that was it.

On these inverters, you only ever talk directly to the display. The display is supposed to forward your commands to the DSP, amongst its own regular commands which try to keep the display up to date.

When warning code 32 is in effect, that means that the DSP is not responding to commands sent from the display (either forwarding commands from the RS-232 port, or its own regular commands). With the wrong firmware in there, the DSP was never going to respond to anything, unfortunately. Yes, it's a pretty crazy setup.

As for before the warning 32, I don't know.

Edited December 10, 2025Dec 10 by Coulomb