6 months using SMA SI’s + EG4 Lithium Wall Mount. SMA solution?

[IAm_Not_Lost]

Posting this for any future users of the - now aging - SMA Sunny Island inverters sold as part of the DC trailers, who are using them in combination with lithium batteries in an open loop setting.

So, despite adjusting the parameters on my Sunny Islands to best match lithium, no matter what, the state of charge would slowly get farther and farther off from the lithium batteries. This was after recalibrating the shunt and adjusting battery size and parameters. I believe it’s mostly due to the lithiums never reaching the top end voltage that lead acids would normally receive at the end of their absorb cycle.

Very frustrating because you can’t prevent the Sunny Islands from turning off if they feel the batteries get down to a low enough state of charge, although you can lower that parameter as far as it will go.

I don’t need the SI’s to monitor, all I need them to be is “dumb” inverters, sort of speak.

So, my solution was to just “calibrate” the shunt while a load was occurring, so that once calibrated it would always sense a slight charge and simply fool the SMA Sunny Islands into thinking the batteries are always charged. For 6 months now that has worked perfectly, and the Midnite Solar charge controllers manage charging the batteries and the batteries have their own monitor, along with me checking.

The EG4’s have worked well, no issues. So nice to not have to water my batteries or deal with venting my utility room all the time.

Thanks!

 

[Ralo]

Nice to see this post. I just ordered some lithium batteries to replay the FLA batteries that came on the trailers and then started reading about the SOC drift. I guess I will follow your lead and calibrate my shunt under load. Now I just have to figure out how to do that. lol Any guidance you can offer?

 

[IAm_Not_Lost]

Nice to see this post. I just ordered some lithium batteries to replay the FLA batteries that came on the trailers and then started reading about the SOC drift. I guess I will follow your lead and calibrate my shunt under load. Now I just have to figure out how to do that. lol Any guidance you can offer?

If you have the SMA Sunny Islands it’s in the manual. The difference is you just do it while the batteries are connected and it’s under load instead of short circuiting the current sensor wires like it calls for.

Page 73.

You just skip to step 6, starting the auto calibration while the batteries are under load. It just makes the inverter think the state of charge is always close to 100% by tricking it into thinking it’s always getting a charge.

You’ll need to put in the installer password into the inverter to allow you to mess in the proper settings (lots of info on how to do this, including the manual).

 

[Ralo]

Actually, I found that the batteries I’m buying will communicate with the SMA inverters through a Ethernet cable for closed loop communication. Check out this configuration guide the google ai did for me.

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gemini.google.com

 

[Hedges]

Have you updated Sunny Island to the latest firmware? It is ca. 2020; quite stable, not daily or weekly updates.
That firmware rev is require to correctly read SoC from BMS when closed loop. Randomly jumping to 0.01 x actual reading occurred with earlier rev.

BMS needs to have its 100% SoC reset parameters correctly set.

Open loop should work too, given correct voltage settings in SI and sufficient charging.

 

[IAm_Not_Lost]

Open loop should work too, given correct voltage settings in SI and sufficient charging.

I would guess he’s probably not using the inverters to charge his batteries. Could be wrong. That’s why I stopped worrying about doing closed loop with the SI’s. All I need them for is inverting and my separate charge controllers charge the batteries.