porzioev

At the end of this post is patched firmware version 264.62, based on factory firmware version 64.62 for the Axpert Max E 11 kW Twin and the '2809 DSP chip. I note that there was a .rar file released where the final conversion to hex file was not created properly, so the update file actually would have flashed to an earlier version. Fortunately, I was able to correct this; for reference, the corrected original factory firmware update file (now in a zip archive) is here:
64.62＿ISOLAR SMW 11KW TWIN recovered.zip
The patched firmware implements all of Georg594's original patches, although one patch (for each MPPT, so two total) could not be exactly applied. I've applied it as best I can "in the spirit" of the original patch. It also fixes the premature float bug, and changes the version number reported by monitoring software to 264.62. The removable display will still show 64.62 (i.e. U1 64 62). The current threshold is changed from 0.50 A to 0.05 A, and the minimum MPPT operating voltage is changed from 90 V to 200 V.
Do not use with any other model, not even the Axpert Max E 11 kW Twin with '28066 DSP chip (but there is a separate patched firmware for that combination). Use at your own risk.
Firmware upload instructions for models with a removable display.
This is the patched firmware (with the original included as dsp_original.hex):
dsp_264.62 patched_200V.zip

verified. It appears that in the latest version 1.15 WatchPower the type of communication of the Modbus RTU (RS485) prescriptions is not supported by the inverter. You need to download version 1.0-1.4 with RS232 support, here it is connected, the data is read.

You can just use any serial comms program; Windows used to come with one, I forget its name. You can send it a carriage return (enter key) at 2400/N/8 (2400 bps, no parity, 8 bits per char). It should respond with what looks like (NAKss .
One step up from that is the Voltronics comms program, which allows you to send commands with CRCs (Cyclic Redundancy Check characters) automatically added. It's probably a quicker and easier download than a full comms program like TeraTerm. Available from https://www.mppsolar.com/v3/download/ and search for 
"communication tool" without the quotes. Suggested command: QPIGS (Query ? ? General Status). It should spit out a string of values like line voltage, battery voltage, and much else. QMOD will give a much shorter response, of the present mode (e.g. "(B" for Battery mode). 
Note that for all of these, you have to ensure that you exited from Watchpower completely with File Exit, not just closing the window. See the Firmware Upload instructions for details.

Axpert RS-232 ports are generally as follows:
+-----------+-------------+----------------+----------+ | Function. | RJ-45 pin # | D9 pin #       | Function | | (PIP)     |             |(provided cable)|(Computer)| +===========+=============+================+==========+ | SGND      | 8 --------- | 5              | SGND     | | TD        | 1 --------> | 2              | RD       | | RD        | 2 <-------- | 3              | TD       | | +12V      | 7 (or 4)    | NC             |          | +-----------+-------------+----------------+----------+