question

nicholas.nouwens avatar image
nicholas.nouwens asked

Multiplus II 48/5000 , Solar MD not reaching full state of charge

Hi,

We have a Multiplus II 48/5000 working with 2 x Solar MD Lithium batteries SS4143 ( 2 x 14.3kwh) as a backup unit, with the intention of installing PV in the next few months. There is a Cerbo GX integrated into the system.

For whatever reason, the system is not charging the batteries to 100%. The "charged" SOC on the system has gradually been reducing over the past few weeks. At the moment, the system will not charge above approx 80%.

The BMS is working and set as the default battery monitor.

I have tried adding and removing the ESS assistant, thinking that selecting the "keep batteries charged" option in ESS will resolve the issue, but with no success.

Would appreciate some input on what I may not have configured properly?

Thanks,

Nick


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Multiplus-II
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3 Answers
kevgermany avatar image
kevgermany answered ·

First guess is that the multiplus battery settings are incorrect. A screen shot of these and also the battery maker's recommended settings would help.

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nicholas.nouwens avatar image nicholas.nouwens commented ·
I’ve checked the settings, and they correspond to the manufactures recommended settings. At the moment I understand that the BMS controls the charge via the GX/Multi
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nickdb avatar image
nickdb answered ·

If you don’t have solar, remove ESS, it only confuses things.

Then step through their setup guide again and make sure it was done correctly.

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Alexandra avatar image
Alexandra answered ·

@nicholas.nouwens@gmail.com

How does the SOC compared to battery voltage and amps? Need to sort out if it is an SOC issue or if charged target voltages are not being reached. (Does it reach 54.6v?)

What are the battery charge and discharge limits? Are both modules online on the logger?

And as suggested check against recommended settings.

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nickdb avatar image nickdb ♦♦ commented ·
And make sure no one has creatively set the managed battery max charge voltage in DVCC.
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nicholas.nouwens avatar image nicholas.nouwens nickdb ♦♦ commented ·

Thank you - checked this and it’s not been selected

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nicholas.nouwens avatar image nicholas.nouwens commented ·

Thank you for your feedback.

The battery is reaching a full charge voltage of 54.6 - 54.9V. At this voltage, the battery current draw is at 0A. I don’t understand why the SOC isn’t reported as 100% by the BMS even though the voltage is OK.

Both battery modules are online.

The Multiplus is in “External Control” mode, so I don’t think that the setting on the Multiplus is the problem here.

I think the issue here is on the BMS not calculating SOC correctly. fb753d5c-e8e6-4e7f-9600-61ae5b3d6730.jpeg5d13bef6-62f9-4092-93fd-58e5ad0f1c37.jpeg

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Alexandra avatar image Alexandra ♦ nicholas.nouwens commented ·

@nicholas.nouwens@gmail.com

Well at least it is partial good news. I guess the next step is to work with solar md for a solution.

If you are able to, can you leave it fully charged for a few days does anything change?

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nicholas.nouwens avatar image nicholas.nouwens Alexandra ♦ commented ·

Even if I leave it on charge for a few days (which has been a challenge with out regular outages) there doesn't seem to be any improvement in the SOC.

I'll follow up with Solar MD and update acordingly

Thanks again!

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