AC coupled battery system

[Stinsy]

That 20kWp array will do you a lot of favours! On bright overcast December days you’ll still get 12.5-15kWh. Not to be sniffed at! Particularly if you have access to cheap rate electric to shift much of your usage into.

Don’t get me wrong you can only expect the above on c. 25% of days in December. The rest of the time you’ll be getting 1-2kWh.

[Oldgreybeard]

I wish our PV array was 20 kWp!

We have the maximum number of panels that we could fit into the roof, pretty much South facing, at 45° pitch, with a peak output of 6.25 kW. That system went live in 2014, so we do still get a decent FIT rate, but our total annual generation tends to be around 6 MWh. This used to be a lot more than our consumption, but now we both have EVs our consumption has risen a fair bit.

It's the battery capacity that should be up to ~20 kWh by early December, and although that's not going to be a great deal of use for storing excess PV generation through the winter, it should at least mean we can run mostly on off-peak electricity, I hope. I just hope the electricity market settles down a bit, as the present crisis seems to have made things go completely mad. Can't even get quotes from some suppliers any more, and the comparison sites are either not functioning or giving warnings that they won't give valid results.

[Oldgreybeard]

The system is up and running with half the batteries (still waiting for the last three to arrive). Seems to work OK, but one slight problem is that the inverter always seems to export a small amount of power to the grid from the batteries when it's in auto mode (about 40 to 50 watts). It's running in auto mode during the day, and time of use mode during the off-peak period.

The small export then causes our solar diverter to think that the PV is generating, so it turns on the water heating, and that then draws power from the batteries. Ideally I want to find a setting that will get the inverter to stop exporting completely. I've been through the various settings a few times, in the hope of finding something that would adjust the import/export threshold for the grid CT, but haven't been able to make head nor tail of some of them.

I'm hoping that I'm not the only one to have encountered this problem, and that someone may have found a setting that fixes this issue.

[Stinsy]

The simple way to overcome this is to set your solar diverter to target 100W of export. This way the inverter and diverter won't fight with eachother and the batteries will charge first, with the diverter taking power when the batteries are full or you max out the battery charge-rate.

[nowty]

The system is up and running with half the batteries (still waiting for the last three to arrive). Seems to work OK, but one slight problem is that the inverter always seems to export a small amount of power to the grid from the batteries when it's in auto mode (about 40 to 50 watts). It's running in auto mode during the day, and time of use mode during the off-peak period.

The small export then causes our solar diverter to think that the PV is generating, so it turns on the water heating, and that then draws power from the batteries. Ideally I want to find a setting that will get the inverter to stop exporting completely. I've been through the various settings a few times, in the hope of finding something that would adjust the import/export threshold for the grid CT, but haven't been able to make head nor tail of some of them.

I'm hoping that I'm not the only one to have encountered this problem, and that someone may have found a setting that fixes this issue.

If you have the SOFAR ME3000SP with the latest software you should be able to use the function below, but I've never used the function myself. I dont know if it actually changes anything or just what the display shows.

16. CT Calibration
Its function is to calibrate grid-connected power.
Select“16.CT Calibrate”,
press“OK”,
“input password”is shown.
Input the password“0001”,
press“Up”or“Down”to change the 1st digit,
press“OK”to switch to next digit,
when“0001”is shown on the screen,press“OK”.
Then input the actual power minus the difference of LCD display

[Oldgreybeard]

If you have the SOFAR ME3000SP with the latest software you should be able to use the function below, but I've never used the function myself. I dont know if it actually changes anything or just what the display shows.

16. CT Calibration
Its function is to calibrate grid-connected power.
Select“16.CT Calibrate”,
press“OK”,
“input password”is shown.
Input the password“0001”,
press“Up”or“Down”to change the 1st digit,
press“OK”to switch to next digit,
when“0001”is shown on the screen,press“OK”.
Then input the actual power minus the difference of LCD display

Absolutely brilliant! Very many thanks, this does indeed fix the problem.

For anyone reading this in future, this setting in the Sofar inverter is really a zero offset, not a true calibration as such. It allows either a negative or positive offset, in watts, to be subtracted or added from the CT measured value. It took two or three goes to get it set to the optimum value, but I now have our indoor display reading an import of between 5 and 10 watts and this no longer causes the PV diverter to try and heat the hot water.

To answer the point made by @Stinsy, there's no easy way to adjust the threshold on the PV diverter, plus adjusting the Sofar like this seems to actually stop the batteries from ever discharging to the grid, so it's a win-win.

[nowty]

Great, when I used the ME3000SP this function was not available and mine used to import 20w or 30w constantly.
The new function is documented in the latest manual, page 38.

https://www.sofarsolar.com/ueditor/net/ ... 210911.pdf

I remember on the old forum, someone even ran the live wire to something like a 10w lamp through the clamp to effect an offset change.

[Oldgreybeard]

Many thanks for that version of the manual, it's different to the two other versions of it that I have! It is a bit clearer, though, so it looks as if they are working on making it more readable. My inverter is running version 2.7 of the firmware, so seems reasonably up to date.

The good news continues, in that the pack charged up to 80% last night, the PV diverter didn't start draining battery power and the pack is now up to 85%, charging from the PV. With luck I may get the battery full charged and still have enough PV to heat our hot water.

I'll be glad to get the extra three US3000C packs, though, as that will make the juggling act between putting enough off-peak charge in to avoid peak usage, but still allow enough spare capacity for PV charging, a bit easier.

[Oldgreybeard]

I may be going doo lally, but I think I remember someone over on the now deleted "other place" who had managed to get a Sofar inverter to communicate with the outside world, without using the (pretty flaky IMHO) Solarman app.

I've built a shed to house the batteries and inverter and what I'd like to be able to do is relay the display on the inverter inside the house, so I don't have to either fire up the Solarman app (which it seems often to take ages to get the current data) or wander out to the shed to read the display.

I've found out that there is an RS485 connection on the inverter that seems to enable data to be read from the thing, and I already have a couple of spare runs of outdoor Ethernet cable going to the shed (about 10m cable length). RS485 should be OK over that distance, so what I'm hoping to be able to do is decode the data from the inverter (I'm hoping it just broadcasts the important stuff) and drive a simple display that shows the PV power, grid power, Battery power and Battery SoC. I don't need any fancy graphics, plots or anything else, just a four line LCD display would be more than adequate and save me from going outside to see what's going on.

I've spent half the day trying to find details of how to do this, gone down complicated rabbit holes where people are making sophisticated apps and stuff, but that all looks to be a massive overkill for what I'm after. I think that the four numbers I want are almost certainly available from the RS485 port, the secret is going to be finding out how to decode them. I can easily knock up a small board with a PIC and a display, and have some RS485 to TTL modules lying around, but I'm missing the key info on how the data from the ME3000SP is configured and formatted.

If my memory isn't playing tricks, I'm sure that someone on the old place worked this out some time ago, and detailed how they'd done it. Damned shame that vast repository of knowledge has now all gone, but maybe there's someone here that remembers how it was done?

[Tinbum]

but I'm missing the key info on how the data from the ME3000SP is configured and formatted.

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