JustinSchoeman

The inverter will try not to let the battery level go below the target SOC. If the battery level does drop to the target SOC, then it will power the loads from the grid instead (leaving the battery idle at the target SOC). If grid power is now lost, it will start discharging the battery until the low voltage cut-off point. If the grid comes back on, then loads with switch back to grid. Additionally, if the 'charge from grid' checkbox is ticked, then it will charge the battery from grid back up to the minimum SOC.

The UI option was not there. When I asked for it, they updated the firmware and pushed it to my inverter in 3 days. That was still a fairly new feature on the SunSynk firmware, and they had not enabled it in the Deye firmware yet.

The Deye and Sunsynk are the same hardware. (Watch the SunSynk factory tour video, and you may notice that the factory is branded Deye.) That said, the Sunsynk UI is definitely better, although, as far as I can tell, actual functionality is the same. Local support for both Sunsynk and Deye are handled by the same company. Second line support is where the real difference is. Queries to Sunsynk international are generally answered directly by Mike, and usually within a day. Queries to Deye international go straight to China, and although they do respond, a lot is lost in translation. That said, the local agents have now got very good first line support, so you should seldom need to go to the international support contacts. As long as you get the WiFi logger, the Chinese engineers will generally log in within an hour or two, and sort out any configuration issues, or let you know if there are external or hardware issues.

I didn't actually get that far. Once I started getting quotes I realized it would by much cheaper to buy from lithiumbatteriessa than to import a small quantity myself. One seller did say that they insist on their own shippers, as they had too many purchases cancelled/disputed when the goods got held by shipping agents and/or port authorities for not having the correct permits. International shipment of dangerous goods can be quite technical, and it is best to deal with a proven shipping agent.

Just remember that bulk lithium battery shipments are classed as 'dangerous goods', and are pretty much restricted to ocean shipping, and even then incur a fair handling charge. Lithium battery sellers often insist on using their own shippers, as customer organized shipments often end up getting stuck with incorrect paperwork.

Polarity of the CT just affects the sign of the measurement, so it could theoretically have been either way around. SunSynk uses the convention that positive is current flow out of the inverter for loads, so you need to point the arrow towards the grid to work with this convention.

That is pretty much what I have done. Only warm spots left are the end plates (flanges) of the geyser, which are largely uninsulated. So maybe not a full geyser blanket - just tape some 'nappies' over the ends of the geyser?

Had the first day of sunshine yesterday, and have some test results... My geyser is a newish Kwikot 150L. No geyser blanket, but hot pipes are insulated. I initially heated the geyser to 75°C. Confirmed that there was no temperature overshoot, and that there were no vents or overflows from the geyser. Then heated it to 80°C and all was still good. Last element activation was at around 5PM at which point the geyser ended at 80°C. By the time I showered at 11PM , it was down to 67°C. After a fairly long shower it was down to 62°C. And this morning it was down to 50°C (still without heating). So the basics seem to work quite well. It will probably require a geyser blanket for similar results in winter, but an off-grid electric geyser is certainly practical. The software does require some work though, as the boost dropout on battery current is too quick (it takes longer than I expected for the MPPTs to ramp up and take over the load).

Finally got my smart thermostat running (although after dark, so no solar boost yet). All the bits and pieces (including reverse engineering a Geyserwise TSE to use for the thermostat) are fairly well documented in the code: https://github.com/justinschoeman/ModbusThermostat Basically performs 3 functions: 1) turn element off when system load is too high, and only turn it on again when load is fairly low (it does rely on most inverters ability to sustain temporary overloads, as it takes about 1.5 seconds to turn off the element). 2) act as a normal thermosts. 3) heat the water as hot as safely possible when there is excess solar electricity available (since this is a bang-bang controller, it probes by turning the element on for a few seconds and if battery draw is too high, turn it off again).

As a matter of interest, I got a call from Geyserwise in response to my request for protocol information. They have a new controller 'Geyserwise Senior' with an RS485 interface for automated management. Unfortunately, they are only sharing the RS485 details with selected developers at the moment, but they are considering releasing it publicly. This would be an ideal controller for home automation/solar optimization.

Browse back in the thread: https://powerforum.co.za/topic/6875-software-for-sunsynk-pylontech-combo/?do=findComment&comment=84414

A lot of BMS's (eg Smart ANT and Daly) expressly prohibit parallel connection. Find out what BMS you are using, and confirm if it is approved or not. I have no idea why most do not allow it - probably due to limits when one BMS opens but not the other. If this is the case, then it should be possible, if you set the total charge/discharge currents lower than each individual BMS.

Sounds a tad optimistic. Could possibly achieve that over a short period purely for the compressed air storage, but once you add turbines and compressors, I can not see how it could be possible.

Oops - forgot about this thread. I eventually had the internal cables made up by ElectraHetrz in Silverton. They were expensive - but cheaper than buying the crimp tool. Jaco @Go-Solar Electrical made up the rest of the cables when he installed the rest of the system.

I think you may be confusing failure modes... Solid state relays are all isolated, and pretty much only a lightning strike could break down the control to load isolation. The main safety drawback of SSRs is that the primary failure mode is fail-closed - i.e. if the output fails, it fails in such a way that it carries on conducting. Mechanical relays can fail closed, but it is extremely rare (something like 1:10^7 for typical relays) - if they fail, they usually fail open - i.e. load disconnected, which is generally a much safer failure mode.

Thanks. I am also planning on targeting 80°C. Not quite within Kwikot's recommended range, but still far enough from any safety limits. Every 5°C is an extra 0.9kWh of 'storage' in a 150L geyser.

Feedback from Kwikot... They say that the highest temp any commercial thermostat uses is 75°C. From the geyser standpoint, the lowest temperature limit is the safety valve, which will start opening at around 92°C. The safety valve is cycle limited to 2 operations, so it is best to stay well away from 92°C. There will be some vertical stratification of temperature inside the geyser, so it is difficult to tell what the maximum safe temperature is at the thermostat pocket. So anything above 75°C is unknown territory.

Has anyone ever reverse engineered the comms protocol of the Geyserwise devices? I would like to use it as a base for an automated thermostat. Hardware is great, but it would be even better if I could use it directly. From what I can see, it seems to be a 2400 baud serial protocol (or possibly 1200 baud RZ protocol, given the odd bit patterns). But I can not see any correlations in the packets when I change temp, or press buttons... If anybody has any previous attempts (even partial) to work from, that would be a great help! Thanks, Justin

As a matter of interest, the stock temperature probe on the Geyserwise is a 10K NTC thermistor with a B value of around 3950. Should be readily usable as is in most home-brew projects.

It is for measuring grid current (for measuring and controlling grid export). That way you can supply/supplement house loads on the grid side of the inverter without exporting to the grid.

Yup - pins 3 and 4 are only used for split phase. For the normal SA ones, it is 5 and 6 only.

Pin 5-6...

It is in the manual (just note that the table is incorrect - the trace labeling in the diagram below is correct):

There were no copyright notices/restrictions in the email they sent me, so I assume it is OK to post it here: sunsynk_modbus.docx

Picture is a 12V - product code is the 230V one (they use the same picture for all the CGB-1C product codes).