rs01

Excellent work @Wiggly Electron and thanks for sharing with the community. The most reliable way to objectively know if your appliances are squealing at 15kHz is to use a sound spectrum analyser app on your phone. Most good cell phone microphones are sensitive to frequencies up to 20kHz. The older you are, the lower the frequency threshold of your hearing, this is a natural process. My kids can hear sounds above 20kHz. I used to be able to hear those. My hearing limit is now around 16-17kHz, so I can just make out the Deye/Sunsynk hum on our appliances. This is a screenshot from an app on my iPhone, you can clearly see the spike at 15k when the phone is near an appliance.

Hi everyone
I have found a solution to the problem. Before you get too excited, I need to say that it isn't an easy nor cheap fix. It also only gets rid of the 15kHz whine on your appliances (output side of the inverter), while the noise from the inverter itself remains unchanged. That being said, it was still worth it for me. Our microwave was driving me insane!
Anyway without further ado, to fix the issue you need to place a big filter inductor on the live line between your inverter and your appliances. The inductor must have a ferrite core (preferably the MnZn type as they have a higher core saturation point). Iron cores wont work as they will filter out the 50Hz power as well and probably cook itself within minutes. I got my E-cores from Mantech Electronics (about R350 for two half cores), although they seldom have stock of these large cores. With these cores you will need between 50-100 turns (resulting in 1-5mH) and the wire size is determined by the amount of current your load is going to draw. I used 10m of 3.14mm^2 enamel wire (sourced from Communica @ R210) which got me about 50 turns and 1.25mH. At 1.25mH it should attenuate about 14dB of the 15kHz noise. After I installed it, I couldn't hear the whine at all. So it definitely works.
Also, another note to those who haven't wound an inductor/transformer yet, it took me a whole day to wind that thing. A solid core wire with a 2mm diameter is quite difficult to work with...
Hope this might help someone.
Regards

Thanks,
Did a Google and seems to be an issue with some SunSynk models that creates interfering harmonics on the power line.
Hopefully SunSynk can fix it for you. 😞

Would be interesting to see a spectrum analysis of the AC in and AC out.

The 8k has some fans and should be installed away from living areas - like in your garage.
The NRS certification is done independently. Sunsynk is sold in UK, EU, US, OZ and many other places that have stricter rules - under the brands Sunsynk, Deye & Sol-Ark
Most people very happy with the SunSynk/Deye inverters.
When is the high pitched sound? It it all the time or during load shedding or when charging or when PV is at maximum load is it when discharging or etc...
1.Never heard of the high pitched issue before.
2.Try Victron - they make some excellent inverters.
3.To sell, try the classified section: https://powerforum.co.za/forum/27-classifieds/

Actually, on all the control boards I'm familiar with, [ edit: which admittedly are quite old now, ] they are roughly where you have D27-D31. So these control boards seem to differ from the ones I know slightly.
There is proper stuff called conformal coating stripper; I have a bottle made my MG Chemicals. But it's probably not worth chasing for this project.
I generally leave it in place, and use sharp multimeter (etc) probes or pins and clip leads. Even then it can be hard. For stubborn pads I just reheat that pad with a soldering iron.

Yes, they sould be something like SN74LVC1G08.
I think this pinout looks very similar, but there may be differences between various models:
https://forums.aeva.asn.au/viewtopic.php?p=94872#p94872
That's possible but probably not worth the effort, if you have a replacement board coming in 14 days.
You would need TI's debug probe, like XDS100. And the first steps with CCS are really not easy. The current version doesn't even have an option to create an empty project, you either have to create it from the command line, or modify some of the examples. Lots of things don't work as expected. Also you need to modify the linker file to only use parts of RAM which are not secured (these DSPs are locked with a password which we don't have).

So thanks to Coulomb, I got the exact 78.08 firmware and changed the derating threshold from 360V to 450V, patched file attached.
Robert1968, you can test it, if you wish. Good luck!
Note for others who haven't read the topic: We don't know why this kind of derating is there and whether it is necessary. Using this firmware may lead to a catastrophic failure of the inverter. Use at your own risk!
MAXE11K_TWIN_DSP_78.08_derate_at_450V.zip

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).

I have been contemplating this method. My first will be insulating the pipes well. Then seeing what the new temp is.
Tell me what does your geyser element draw for preheat? I know they are 3kw. I ask this is we have a smaller system. Be great if it just did 1kw.lets say

Well to preheat the water makes a huge difference in water temp in winter and gas consumption.
I have a 16l gas geyser for 2 bathrooms, It was connected straight inline with the hot water line to the taps, bypassing the electric geyser completely.
with this setup I used 9kg every 9 to 14 days depending on the season. My outside pipes is insulated with much cheaper pipe insulation, I saw the pipes in my roof was insulated with old cloth and rags bound around the pipes with twine, and that also works.
about 6 month ago I put my electric geyser back inline to preheat and feed the gas geyser, I set the geyser thermostat to 40 degrees and changed the element to a 2kw unit.
I use 4kw/h to pre-heat the water (150L) thats fed to the gas geyser, in the dead of winter with only the gas geyser heating the water I could not get the water temperature above 45 degrees.
now with the preheated water the temperature easily reaches 80 degrees in the summer(80 degrees is the geyser's cut out temp) and I have not seen the water temp below 55 degrees and the gas geyser is set to max water flow and min gas, and this have resulted in a 9kg gas bottle lasting 25 days plus....