Automating overnight charge rate and limit with Sunny Island

[jonc_uk]

Hi All,

I have switched out my Sofar ME3000SP inverter-chargers for Sunny Island 8.0H. I am using the system for self-consumption without battery backup and fully charge the Pylontech batteries overnight in the cheapslot.

However, now we are in February, the PV means the batteries are typically not completely empty before they start charging again. As the system is set, this means the full charge finishes early.

This is ok, except that if I were able to turn down the charge rate, the charge efficiency increases. Also, as the longer, sunnier days approach, I don't want to charge to 100% overnight (although this will depend on the following day's weather).

I appreciate that I can modify the charge rate/times manually via the Sunny Portal, but I would like to automate this. I imagine I could do it by proxying and altering the battery CAN data to force a lower charge rate or SOC but this seems like a dirty hack.

Any other suggestions?

[Kommando]

Which version of the 8.0H do you have,10 , 11, 12 or 13.

[jonc_uk]

SI8.0H-13.

3 actually as a 3-phase group.

[Kommando]

With a 13 as well as changing parameters using Sunny Portal then you also have the option of Modbus TCP.

Depending on the firmware version there are two modbus register lists

https://www.sma.de/en/service/downloads ... c491e47952

What I would do is to first check that you have modbus access, you may need to turn it on using the Sunny Portal and set a Modbus ID (use 3 if available, 1 and 2 are used by the Webbox which is a legacy bit of hardware.

So find out your SI's IP address and Modbus ID and us this program installed on a PC plus Java to test read some registers.

https://github.com/SciFiDryer/ModbusMechanic

Once you have confirmed access to Modbus TCP on the SI then use Node-red with the Modbus nodes installed to write to the modbus register that controls charging using the grid using a timer node to write the on and off values.

Node-red can be run on a PC for writing the node flow and testing, once its working then import the flow into a Raspberry PI and at a lower power overhead it can take over control. You will access the Node-red flow on a website using a browser to say change timings based on different tariffs.

A node-red flow I use to turn on and off loads to keep my SI from throttling back the Sunny Boys as an example.

Note that writing a wrong value to a register could brick your SI, so be 100% sure before starting to write values to a register.

[jonc_uk]

Thanks Kommando - very helpful.

Lots of fun to be had playing with this..

I have turned on Modbus via the installer login on the SI. I don't think it can be done via the Sunny Portal.

Modbus Mechanic is giving me results via slave node 3 - I could not find a parameter on the Installer login on the SI for this so it may be hard-set to 3.

Lots of reading of the parameter list now, and getting my head round how the system is normally controlled. Looking at the event log on the SI, I can see the switching from self-consumption to charging:

23:30 --> Self-consumption control stopped
23:30 --> System control: Setpoint spec. activated

..and back again:

05:30 --> Self-consumption control started
05:30 --> System control: Setpoint spec. deactivated

..which I assume is the Sunny Home Manager sending it's commands.

Just need to work out the registers to write for these.

[Kommando]

Luckily you will end up only interested in 5 or 6 registers but with SMA providing so many registers and the descriptions not always matching the matching parameter description in the Sunny Portal its a steep learning curve.

Note any register marked ! in a yellow triangle is best left alone

Warning against cyclical writing - Cyclic modification of these parameters may destroy the flash memory of the product