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Rasmus Mikkelsen avatar image
Rasmus Mikkelsen asked

Mppt goes to absorption before set voltage

Hi all, I'm struggeling to figure out this problem.

As you can see my batteries are not near full, my batt voltage is 55v, should hit absorption at 56.7v using 18650 lithium cells.

But system went from bulk to absorption already at 55v, that means the mppt is holding back on charge current.. If I turn on a 2kw heater you can see the PV power goes way up, and goes down when I turn it off.

Here's a video I took from last weekend, trying to illustrate it. I would want all the current going into my batteries, I only charge to 4.0v / cell currently at 3.9v so should just dump all it can at the moment. It's quite weird to me, bms charge target is 100a atm.

https://youtube.com/shorts/Z2UW2XZulUI?feature=share

If I set absorption and float higher in the app, it kinda ignorer this, I just tried to set it to 58.8v for both abs. And float and reboot mppt, same goes directly into abs. Mode. And tapers down current

I hope some of you can help me out with this strange problem :-)

Have a great day

20221002-105333.jpg



MPPT Controllers
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5 Answers
Rasmus Mikkelsen avatar image
Rasmus Mikkelsen answered ·

I see my picture didn't go through

It is possible i have a setting somewhere i have missed, im trying to learn :-)
screenshot-20221002-105321.jpg20221002-105501.jpg


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Alexandra avatar image
Alexandra answered ·

@Rasmus Mikkelsen

The main difference bakeetween bulk and absorption is the current drawn by the battery.

Do you have a shunt as well?

If the internal resistance is going up then the amps going to the bank goes down.

I dont see a tail current set? Is there a reason for that? This thread discusses more on its effect.

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Rasmus Mikkelsen avatar image
Rasmus Mikkelsen answered ·

Hi Alexandra thanks :-) I have the batrium shunt, and currently 400ah of batteries. Uhm tail current, I was under the impression that wasnt for lithium hmm, will have a read

I guess my problem currently is down to mppt going into absorption at 55v, while it's set to 56.7v.

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Alexandra avatar image Alexandra ♦ commented ·

Tail current switches it into float at the end. But for it to go to float is has to reach the charged voltage. So not an immediate thing right now.

Have you checked what voltage is shown/detected at the mppt terminals?

How balanced are the cells?


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Rasmus Mikkelsen avatar image
Rasmus Mikkelsen answered ·

Hi all, I am also wondering why my victron connect app says that mppt is externally controlled. Is this because of my bms (Batrium)? It's wired via can to Cerbo GX

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pwfarnell avatar image pwfarnell commented ·
Yes, this explains why your MPPT settings are being ignored, the BMS is controlling the charging and you need to make your changes in that device. The BMS should also control the Multiplus. See my comment on SOC vs Voltage above, do you have the correct specs for your cells, do you know the correct settings because you appear to have some confusion on the basics.
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Rasmus Mikkelsen avatar image Rasmus Mikkelsen pwfarnell commented ·

I know the correct specs of my batteries. I don't see my self as an total newb, but only had the system running for little over a week, and trying to correct a few things :-)

The bms software is also new to me, and not very familiar or experience with it yet, will come with time. I however believe I have all the correct settings in the bms. Will double check when home after work.

I'm wondering if there's a bug in the bms software, because one of the charge settings is set to 56.00v and it won't charge higher than 55.00v atm.

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Rasmus Mikkelsen avatar image
Rasmus Mikkelsen answered ·

Just to follow up on the problem.

I stumbled upon this topic. What solved my issue was, go into settings and DVCC menu, change that voltage setting there.

I would assume this has solved it for me, just waiting for some sun to see, fingers crossed.

Thanks all for helping

https://community.victronenergy.com/questions/12525/mppt-networked-operation-charge-voltage-to-low.html

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