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wysiwyg asked

SOC not recovering to 100%

Hi ,

I am using the following equipment: Multiplus 48/5000/70-100 Firmware 486, MPPT 150/100 v1.59

Only been installed over a month, getting the SOC reading from the Multi, only use solar to charge as there is no grid or generator input yet. Since a few days ago the SOC level has just kept dropping and never recovering back 100% charge even after full recharge from solar. Is this a common problem and is the only way to fix is to install a dedicated BMV like a smartshunt?

Note: I have not performed any updates or system changes during this time.

Images attached:

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screen-shot-2021-08-30-at-093037.jpg

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MultiPlus Quattro Inverter ChargerSOC
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screen-shot-2021-08-30-at-093037.jpg (41.4 KiB)
screen-shot-2021-08-30-at-093100.jpg (47.7 KiB)
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8 Answers
taylortops avatar image
taylortops answered ·

Can you show Battery Watts? I'd suggest your area above the line is smaller that the area below the line, ie, you're pulling more than you're pushing. Are your panels shaded shortly after sunrise? They should be facing mid-winter noon elevation.

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wysiwyg avatar image
wysiwyg answered ·

I have a 48V system (1650Ah), only run a 70-80w load 24/7 on it. Panel array is facing north with appropriate elevation.

Battery watts below:

screen-shot-2021-08-30-at-132807.jpg


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wysiwyg avatar image
wysiwyg answered ·

Does not make sense!


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Kevin Windrem avatar image
Kevin Windrem answered ·

The only way the Muti's internal SOC calculations is accurate is if it is the only charging source and load. Since you have a PV charging source, it is not being included in the SOC calculations. Add a BMV or smart shunt to your system so it can measure actual battery current which is a combination of the Multi and the solar charge controller.

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wysiwyg avatar image wysiwyg commented ·
Thank you for that, I assumed that would be the case.

Not sure in what real world application you would have the Multi ever being the only charge and load source, only instance that I can think of would be using a generator or grid power to charge your batteries with no solar???? Whats the point then?

Thanks

Mark


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shaneyake avatar image shaneyake wysiwyg commented ·
As a UPS is a big real world use but you can also have AC-Coupled PV.
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wysiwyg avatar image wysiwyg shaneyake commented ·
Good point, did not think of that scenrio.
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Matthias Lange - DE avatar image Matthias Lange - DE ♦ commented ·
@Kevin Windrem That is not correct. With a GX device the energy charged by a Victron MPPT is used to calculate the SOC.

But it is possible that you have to adjust the settings for the internal battery monitor.

"Charge efficiency" and "SOC after bulk"

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wysiwyg avatar image wysiwyg Matthias Lange - DE ♦ commented ·
Tried all that, nothing seems to work. The MPPT SOC shows different values to Multi SOC in the data. System only allows me to select battery monitor "Automatic", "Multi" or "None" does not allow the MPPT to be selected as the battery monitor.
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klim8skeptic avatar image klim8skeptic ♦ wysiwyg commented ·

There is an Victron youtube video that might help explain things.

Victron YT videos.

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wysiwyg avatar image wysiwyg Matthias Lange - DE ♦ commented ·
Thanks again fo your response, do you have any suggestions on "Charge Efficiency" and "SOC after Bulk" settings that will fix this issue in that case?

I use a Venus GX device with this setup as well and I am familiar with remote VE Configuration.

At the moment I have default values as the battery monitor in VE Configuration file. 85% after bulk has finished, 1650AH and 0.80 charge efficiency.

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Matthias Lange - DE avatar image Matthias Lange - DE ♦ wysiwyg commented ·
What kind of batteries do you have?
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wysiwyg avatar image wysiwyg Matthias Lange - DE ♦ commented ·
AGM
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nickdb avatar image
nickdb answered ·

In an ESS environment, the multis are just not good at tracking charge. We had the same issues a while back. You will need a smart shunt (or batteries with internal management) and set it to sync the battery charge when the right levels are reached.

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wysiwyg avatar image wysiwyg commented ·
I think that is the way to go, no point flogging a dead horse! Thx
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JohnC avatar image
JohnC answered ·

Hi @wysiwyg

I'm rusty on the Multi's SOC, and I never used it myself when I had nothing else.

It can use the mppt current to credit SOC, but I don't think it will do that when the Multi hasn't reached it's set Absorb V. There's probably good reason for this, but I never bothered really pursuing it.

But the Multi's set Abs V isn't necessarily the same as the mppt's actual. Temp compensation can change that, and given that your mppt output was getting registered over the first few days, then lost it, suggests this at play. If you had DVCC invoked (both SVS and STS) and temp-comp settings identical, then I'd expect it to work. Even then I'd have the Multi's Abs set 0.1V lower to make sure, and give the solar priority as well over grid/gen charge sources.

To test this, try lowering your Multi's Abs V setting by (say) half a Volt or more.

Really, this SOC isn't inherently suitable for a 'creep-up-on-it' charge like solar. The shunt based kit is far superior. And if you're not using DVCC (free!) then consider that too.

A side question.. Do you really have 1650Ah of agms (at 48V)? That's like ~2 tonnes of batt?

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wysiwyg avatar image wysiwyg commented ·
1.3 tonnes to be exact :)

Thanks for the info.

The system has actually been reporting a correct SOC for 25 days, its only in the last 4 days its started reducing. It has been warmer in the last 4 days, so temp may have some part to play in this.

I will try your suggestion and reduce the abs V on the multi.


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wysiwyg avatar image
wysiwyg answered ·

Here is the SOC vs Batt Temp graph, ever since the battery temp reached 3 degrees, the SOC has been steadily dropping. Not sure if that has anything to do with what is happening.

screen-shot-2021-08-30-at-224004.jpg


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nickdb avatar image
nickdb answered ·

Have you considered enabling temperature charge compensation?

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