Tail current 3 MPPT

Question

question

jolilo asked Nov 29, '23

Tail current 3 MPPT

Hello everyone

I have three MPPT 150/32 2BS and 1 SS chargers

in // on a 48v battery

connected to a multiplus II

my question how the tail current works because I noticed if I programmed a threshold at 2A on each one it is the first one which goes below the threshold which forces the SOC to 100%

but there are three MPPTs in // therefore the load is still higher than the threshold and distorts the SOC

how to do it thank you

I deactivated the three tail currents

now it's worse! I can't even determine who or what is calling the SOC

how to do it thank you

Need help

SOC

2023-11-29-18-48-29-victronconnect.png (60.8 KiB)

2023-11-29-18-50-04-victronconnect.png (50.5 KiB)

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Modifications Space

Node Red Space

Answer 1 · 2023-11-29T18:37:05Z

Alexandra answered · Nov 29, 2023 at 06:37 PM

@jolilo

Do you have a shunt to measure SOC?

Are the batteries communicating with the Cerbo?

If the battery is not, then each MPPT will be doing its own thing.

In system set up under settings what is set as the battery monitor?

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Answer 2 · 2023-11-29T18:49:04Z

jolilo answered · Nov 29, 2023 at 06:49 PM

thanks for the help

Do you have a shunt to measure SOC?

no

Are the batteries communicating with the Cerbo?

no

If the battery is not, then each MPPT will be doing its own thing.

how to synchronize the 3 MPPT

In system set up under settings what is set as the battery monitor?

view the photo

2023-11-29-19-41-03-terrabos-vrm-portal-maxthon.png (59.3 KiB)

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Answer 3 · 2023-11-29T18:56:54Z

jolilo answered · Nov 29, 2023 at 06:56 PM

SOC jump detail

2023-11-29-19-59-30-2023-11-29-19-52-13-terrabos-v.png (22.6 KiB)

1

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Alexandra ♦ commented · Nov 30, 2023 at 04:27 AM

The inverter SOC when bulk is finished is likely at 95%. The ve bus SOC is more of a calculation and when there are other charge sources it is not accurate. Will also be made worse by the sudden tail current drop.

You need a Shunt for more accuracy.

Set up each MPPT as if they are stand alone, so they can charge correctly.

All sources should have the same voltages set. Check that they all read correctly as well.

Tail current is whatever it takes to get the cells balanced.

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Answer 4 · 2023-11-30T12:05:06Z

jolilo answered · Nov 30, 2023 at 12:05 PM

Hello, Alexandra.

and thank you

I wanted to save on a shunt

state of charge at the end of the bulk phase is set to 92%

you can see it clearly in this image

and we can see very clearly the second jump of SOC

another question how to bring up a topic

I had a question that remains unanswered

https://community.victronenergy.com/questions/197660/colors-widget-are-not-respected-on-the-display-why.html?childToView=240809#answer-240809

2023-11-30-12-59-58-terrabos-vrm-portal-maxthon.png (36.6 KiB)

2023-11-30-13-04-28-ve-configure-3-multiplus-ii-48.png (38.1 KiB)

2

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JohnC ♦ commented · Nov 30, 2023 at 12:59 PM

Hi @jolilo

I'm curious. You haven't mentioned your battery type, but you have a fixed 30m Absorption duration set. That suggests Li batteries given the 30m to balance their cells. And your V's don't match typical Pb's. Li's are usually considered very close to full when they reach Abs.

So if they are Li's, you shouldn't be using that Tail function anyway. And your Multi's SOC setting when Bulk stage is over should be up near 100%.

If you want to bump that other question, just add another comment asking again. I thought that was all fixed, mine was but it took a while. Might be platform/browser related, so provide more detail. Or you could try rebuilding a fresh widget.

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Alexandra ♦ JohnC ♦ commented · Nov 30, 2023 at 04:18 PM

@jolilo

It would seem your battery when bulk is finished would.be closer to 98% then not 92%.

If you say it is 98% efficient then in theory that is when bulk is finished.

The jump up in soc after the tail current and voltage is reached suggests that anyway.

For our interest where did the 92% figure come from?

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Answer 5 · 2023-11-30T13:28:18Z

jolilo answered · Nov 30, 2023 at 01:28 PM

Good morning, John

thank you for your

it's a lifepo4 battery

I want to use the queue function

but I have 3 MPPTs in parallel and that's my problem, it's the first one that goes below the threshold that blows up the SOC

I tried in two different browsers and it's still the same for the color problem

however the edition is good

2023-11-30-14-26-50-maison-monteils-vrm-portal-moz.png (25.4 KiB)

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