Files

Deprecated! Use patched firmware version 156.05 instead, which patches MPPT2 as well as MPPT1. I will delete this download when 156.05 is tested.
This is temporary patched firmware version 256.05, based on main firmware version 56.05 for the Axpert Max II 10kW. it changes only two things (apart from the version number): it fixes the premature float bug, and changes FOR MPPT1 ONLY the current at which it switches behaviour from 0.50 A to 0.05 A. MPPT2 is not changed, so that some users with similar arrays connected to MPPT1 and MPPT2 can compare the effects.
If this works, I'll patch MPPT2 similarly. If if doesn't, I'll do the full set of "stuck at 90 V" patches.
This firmware is for the TMS320F2809 processor, which is the one with the two voltage regulators (see this post). Do not use with other inverter models. 
Original dsp.hex is dated 2022/Mar/16. Hence factory firmware version 56.05 appears to supersede Axpert Max 10kW firmware version 90.01.
Use at your own risk. 

Dyness B51100 User Manual
Revision Number: 1.0 
Revision Date: 2021-12-01

I found this in my downloads folder recently, and it seems to be one answer for a number of problems, such as parts of the display flickering intermittently, especially models with the colour display and round LED ring. In a separate .docx document (not attached here), it says:
[ Edit: Axpert MKS IV models (under their various names) should have this modification provided from the factory from about August 2022, according to one reseller. ]
[ Edit 2: See also this post for a way to rearrange the wires to the MPPT inductor; it worked for at least one poster. ]
I note that the capacitor part number (a Voltronic part number, you can't order from an electronics retailer with this number) mentioned above is different to that of the PDF in this download, so I may be conflating fixed. However, the rest of the .docx document has almost verbatim the same text. The docx document mentions an 18μF 600 VDC capacitor, but that would be much larger than the one pictured. If you don't order the part from your supplier, I suggest about a 2.2μF 600 VDC X2 class polyester film capacitor.
DANGER!
PV voltage on these models is lethal! The charge on the capacitor will persist at a lethal level possibly for hours even after the PV is isolated, so ALWAYS test first with a decent multimeter. Do not touch the terminals if the voltage is above 50 VDC. If you don't know electronics, DO NOT ATTEMPT THIS!
This modification may make your inverter significantly more dangerous to work on. If you are in the habit of working on the PV wiring, you might want to reconsider performing this modification. Maybe the circuitry will quickly discharge the capacitor, I don't know as I don't own one of these models.
DANGER!
There is also talk of a metal shield, and possibly an inductor, but I can't quickly find this thread. Hopefully, this will help someone, or at least point them towards a solution.

This is main (U1) firmware for the Axpert VM II, and probably also the PWM versions thereof (probably called an Axpert VP II or just Axpert VP 3K-24 or similar). This file contains both version 20.13 (2018) and 20.14 (November 2022). It supports 5 kVA, 3 kVA and 1.5 kVA models, all PF0.8 or PF1 (selected by resistors at start-up), except that the 1.5 kVA model is PF0.8 only (1200 W). I can't recall where I found this firmware. Do not use with any other model.
Use at your own risk.
Firmware upload instructions.

Felicity Solar Lithium battery pairing with Deye/SunSynk, Growatt SPF Series and Voltronic Power (Kodak/RCT/Mecer) Axpert and InfiniSolar Inverters 
 
SUMMARY
Deye/Sunsynk
1. Communication Cable Pin: 5,6(Felicity, any port)——> 1,2（Inverter, RS485/BMS port)
2. Setting steps on inverter: SAT→BATTERY->SETTING->LITHIUM->LITHIUM MODE→12
3. Sign of successful communication: Check the battery SOC on inverter
Growatt SPF series
1. Communication Cable Pin: 5,6(Felicity, any port)->1,2（Inverter, RS485 port)
2. Setting steps on inverter: Setting->005->Li->036->L04. 
3. Sign of successful communication: Check the battery SOC on inverter
Voltronic/Kodak/RCT/Mecer Axpert and InfiniSolar series communication. 
1. Communication Cable Pin: 5,6(Felicity, any port)->3,5（Inverter, BMS port)
2. Setting steps on inverter: Setting->14->PYL. 
3. Sign of successful communication: Check the battery SOC on inverter

Hi,
 
With the assistance of @BritishRacingGreen, I have compiled the following document so that the step by step installation instructions exist for those who are experiencing Ghosting, floating Neutral during Load shedding. Noticed by a faint glow in lights even lights are turned off.
Ghosting = Experiencing during load shedding a Voltage potential between Earth and Neutral on the Output side of the inverter.
Hope you find the guide as useful as I did the great assistance from @BritishRacingGreen
Total time for installation and setup: 30 minutes
End result: 0V potential between Earth and Neutral during load shedding, same as during no load shedding - Ghosting gone.

WatchPower  VER 1.16 SP9

"Wiring Unlimited" is a book from Victron about electrical wiring systems containing batteries, inverters, chargers, AC and DC wiring etc. and with some useful theory.
This is not only about Victron, it is generic and is very useful information anyhow.
 

This is main firmware version 71.10 for the Axpert MKS III or PIP-5048MGX, and other names. It is for the '2809 DSP.
Do not use with any other model, or with any model that comes with firmware other than 71.xx.
Beware of version numbering clashes; 71.xx firmware exists for the 5 kVA Axpert King 1, Axpert MKS II, and Axpert MKS 1 PF1 64V.
Use at your own risk.
Firmware upload instructions.

Hello,
This is the translation file for MultiSIBControl for French.
It should be copied to the Lang folder of MultiSIBControl.
If you want it to be started by default, you can rename it to English.txt because the software does not remember the language choice.
 
Bonjour,
Ceci est le fichier de traduction en français pour MultiSIBControl.
Si vous souhaitez qu'il soit chargé automatiquement par défaut au démarrage de l'application, you pouvez le renommer vers English.txt, car il ne conserve pas le choix langue. 
 

I found this service manual in my collection. There are a few partial schematic diagrams, but not much detail, as is usual with these manuals.
This is an EASun branded PDF, but it looks very much like it came from Voltronic, hopefully legitimately. EASun do seem to be a legitimate Voltronic reseller these days.

This is unpatched main (U1) firmware version 74.04 for the Axpert MKS IV. Do not confuse with the Axpert VM IV which looks similar, or the Infinisolar V IV which looks identical (possibly apart from the colour). This will not work if you happen to have a model that comes with the '28066 DSP chip; see this post for details.
Firmware upload instructions.
Use at your own risk.

This is unpatched main (U1) firmware for Axpert Max 7.2kW. dsp.hex is dated 2022/Sep/11. Like all factory firmwares for Axpert Max so far, it has the premature float bug and the stuck at 90 V MPPT bug. Provided here as a failsafe/backup.
Use at your own risk. Do not use with other Max models, clones, etc. Compatible genuine models include the Kodak OG-MAX 7.2, PIP-7248MAX, and many more.
Edit: Do not confuse with patched firmware version also called 90.19 (not mine), based on this factory firmware.

Includes NT1.8+ST2.8 chipset versions

Scanned in product manual for Shoto SDC10-Box-5, 5.12kWh.
But hard to find manuals for this specific model online. Could not find a searchable PDF doc. And can't find the original URL for this file anymore.

This is factory (un-patched) main DSP firmware  v.69.05 for Axpert Max 1 (with removable display) 7.2kW with the new processor ('28066) from Tommatech (re-brand of Axpert/Voltronic)
Changes from previous versions unknown.
The zip file contains SOP for upgrade using Tommatech/Arena tool.
Use at your own risk (if your original U1 is 69.00)

This is main (DSP, U1) firmware version 72.04 for the Axpert Max 1 8kW inverter with the TMS320F28066 processor. Only use this firmware if your existing firmware starts with 72, and it's an Axpert MAX 8kW with the removable display (there are several other firmwares starting with 72 for totally incompatible models).
Firmware upload instructions.
Use at your own risk. 

This is patched firmware version 281.05, based on factory firmware version 81.05, for the Axpert MAX II 8kW with a TMS320F28066 processor. It will display as 81.05 on the front display, but as 281.05 on monitoring software.
This firmware should simply not update if your inverter is the type with a TMS320F2809 DSP processor. Use only if you know that your processor is a '28066, e.g. if your main firmware from the factory was version 81.xx.
The arena reflash tool is included.
This patched firmware fixes the premature float bug, and implements PV patches to prevent the panels from being dragged down below 200 V (was 90 V). This allows the battery to fully charge from solar, and increases PV production, especially in cloudy conditions.
For upload instructions, see https://forums.aeva.asn.au/viewtopic.php?p=87767#p87767 .
As always, use at your own risk.

READ THE INSTRUCTIONS FIRST: https://powerforum.co.za/topic/2322-youdas-off-grid-lab/?do=findComment&comment=151032
Firmware for Pylontech low-voltage batteries:
US2000B Plus US2000C (original chip) US2000C (new chip) US3000 US3000C (original chip) US3000C (new chip) US5000 (original chip) US5000 (new chip)

This is factory firmware version 56.04 for Axpert King 3kW Rack Mounted models with the '28066 processor. The nominal voltage is 48 V despite the "3.24" in the original rar file name. dsp.hex file is dated 7/Oct/2021.
Do not use with any other model, and only if the existing firmware is 56.xx. Note that there are several other models with 56.xx firmware, do not confuse them.
Use at your own risk. 

PDF - Pylontech FW upgrade SOP

This is factory (not patched) removable display firmware version 102.73. Note that you can only see the leading "1" from monitoring firmware; from the front display, it looks like U2 02 73.
WARNING: Only use this if your existing display firmware version starts with a "1"; I suspect that the leading "1" is important, and indicates a difference in display hardware.
Ignoring the above may result in BRICKING YOUR display, which will necessitate getting a new one. Apart from the expense, delay, and hassle, it will be difficult to obtain the exact right display model, as they are many with subtle differences.
This firmware release has a rare factory release note: "More increasing the reliability of communication of Pylontech version "C" Li batteries with the display and VM III / KING converters".
This removable display firmware is ONLY for the Axpert King or the Axpert VM III, though these are known by different names by different resellers.
 

Firmware update to U20.14 from 20.13 for the Axpert V 5kw PWM model. 

Resolved an error 8 issue when paired with a Li-Ion battery.

Only use in case your battery is bricked after normal flashing with Batteryview didn't work.
Preferably first contact Pylontech tech support!

This is patched firmware version 291.70, based on factory firmware version 91.70, for the Axpert MAX 11kW with a TMS320F28066 processor. It will display as 91.70 on the removable display, but as 291.70 via monitoring software.
WARNING! This firmware will not work if your inverter is the type with a TMS320F2809 DSP processor. Use only if you know that your processor is a '28066, e.g. if your main firmware from the factory was version 73.xx. If you get this wrong, the upload will refuse to work, but it should not brick your inverter (just restart).
The arena reflash tool is included.
This patched firmware fixes the premature float bug, and implements PV patches to prevent the panels from being dragged down below 200 V (was 90 V). This allows the battery to fully charge from solar, and increases PV production, especially in cloudy conditions.
For upload instructions, see https://forums.aeva.asn.au/viewtopic.php?p=87767#p87767 .
As always, use at your own risk.