question

jasebri avatar image

Multiplus II does not refill?

So this is a brand new installation at home, mounting twelve 450W panels, with a Multiplus II 48/5000 inverter, 2 Victron MPPT (150/60-250/85) and 2 lithium batteries (51,2 volts, 61 Ah), color control. Conected to the grid as backup (or at least that was desired). I am a bit concerned about its perfomance as I am an absolut ignorant about this matters and it seems a bit weird to me:

The panels start to fill the batteries every morning, and around noon they are charged . From then, the "method" changes, and the amount of charge they will receive is always lower than the energy consumed in the house. I.E.: (Sun shining, 11:50 AM, Canary Islands), B attery level 82%, AC Loads: 230W, PV Charger: 214W!!! , then I switch the vacuum cleaner: AC Loads 1827W PV Charger 1153W!!!. Why did the PV charger did not get 230W at 10:50 if there was sun quite enough???

So there is enough insolation to refill the batteries or at least preventing their drain, but this does not happen. They continue slowly draining even when the sun is bright and strong, and when it goes in the evening, they have 15-20% less than they should do. So every early morning the system gets power from the grid earlier than desired.
bateria-20dic.png
My question: is this normal behavior of the Multiplus II?. Please answer as if you were talking to your 7 years son. Thanks a lot.
Multiplus-IISolar Panelgrid
bateria-20dic.png (15.9 KiB)
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9 Answers
snoobler avatar image
snoobler answered ·

Many battery manufacturers indicate that LFP does not need to be floated. That is true if you're just placing them in storage. However, when using them in cyclic power system, a float voltage is needed so the MPPTs provide solar for loads trying to pull the battery voltage down.


Set float voltage to 3.4V/cell, 54.4V.


SoC curve will look like this:


1640123282262.png


Given that you are only achieving 90% SoC, you may wish to review how you're charging the battery.




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seb71 avatar image
seb71 answered ·

Are you using ESS?

You should not discharge the battery to 0% SOC (at least not when grid is available). If that really is 0%.

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jasebri avatar image
jasebri answered ·

thank you so much for your answers. Yes I think ESS is what I use. I was told that as batteries were lithium, discharging them to 0% was not an issue.


Any idea why batteries don't reach 100%?

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Discharging to 0% isn't an "issue", but it's not best practice. For maximum cycle life, you don't want to discharge below 20% regularly. Discharging to only 20% may double the life of the battery.


Your MPPT and BMV settings likely are not set appropriately, and your battery is getting to near 100%, but it's just not accurately reported.


It's uncertain why your SoC drops when you still clearly have solar available in excess of your loads. We will dig into this after sorting out the MPPT & BMV.


EDIT: Based on your device list, you don't have a BMV. If your system is using the battery monitor in the Multiplus, that would explain why it's not getting to 100%. Please post a capture of your battery voltage and current for the same period you posted for the SoC.


This is what you asked for?
screenshot-20211223-003833-chrome.jpg

kevgermany avatar image
kevgermany answered ·

Please post the settings of the MPPTs and multiplus.

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I would love to, but I'm the final user, I have no idea how to reach that, it has been set by the dealer.
If the MPPTs are smart, you can connect via Bluetooth using the Victron connect app. The multiplus really needs a special cable.

But your installer should be getting this sorted properly.


seb71 avatar image seb71 kevgermany ♦♦ ·
He can download the Multiplus settings using VRM.

Thank you SO much Seb. I have access to VRM but my user is limited to MONITORING. I think I can't reach the settings this way, can I?

I will try to find out the blutooth thingl.

If you have access, it's under "Device list" - "Remote VEConfigure".

Perhaps there is a users guide?

device-list.png

I think in Monitoring access there is no such option

device-list.png (51.0 KiB)
seb71 avatar image
seb71 answered ·

While lithium batteries can be discharged to zero, doing so often will reduce their lifespan. If you are using ESS, in your ColorControl GX you have a setting named "Minimum SOC (unless grid fails)", which apparently is set to 0%. Increase that to at least 10% (or, even better, to 20%). But you should also check the battery voltage and cell voltages, especially when the battery is (close to) empty and when it is full.


I would love to, but I'm the final user, I have no idea how to reach that, it has been set by the dealer.

Either ask these questions to your dealer or start by reading the manuals of all your components (and after that you should be able to post the settings).

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snoobler avatar image
snoobler answered ·

If those VCSF files contain the actual config of your MPPT, your installer did NOT set your MPPT appropriately at all, especially for Lithium.


You need to IMMEDIATLY DISABLE temperature compensation.


Revise BOTH as follows:


1640184619564.png


If you have a BMV-712, please upload it's configuration.




1640184619564.png (120.4 KiB)
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thank you VERY much. What risk have I been running with the original settings? May the batteries be damaged?
I changed as you said and now it's taking electricity from the grid to charge the batteries! (it's nighttime)
Since the batteries likely have their own protection BMS on board, little risk of damage.


The ESS settings may have triggered charging due to the settings. I'm guessing at that.

I entered in panic and set it back to where it was, then sent your instructions to the dealer to see what they have to say. Can they reach MPPTs configuration remotely?

With VRM, a "Full Control" user has total access, so I would presume they can remotely configure all GX attached components.


I routinely manage my system with VRM and make changes as needed from 3.5 hours away.


snoobler avatar image
snoobler answered ·

1640227903996.png


I've drawn vertical lines to find the same time on each chart. Your voltage is mostly constant (blue line), and the current is mostly constant (orange line), though it does appear the current is slightly negative. This doesn't make a lot of sense.


You do indeed appear to be losing that ~5% SoC even with available solar.


This is likely a calibration or configuration issue, and it shouldn't be like this. You should contact your installer to have them resolve it. It's not working as it should, and they should fix it.


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seb71 avatar image
seb71 answered ·

If you are using ESS, then the MPPTs are controlled by the Multiplus.

It's still good to have the MPPTs configured properly for your battery, but as long as ESS works as it should, these settings will be ignored (except the charge current).


As I said, if you have to change the settings, first read the manuals.

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So MPPT configuration is ignored by Multiplus?

Thank you very much for your answer. You are quite right that reading the manual is key, but to understand what it says you must first have basic electricity knowledge, wich I lack absolutely. I'm not sure about the difference between a volt and a watt.

ESS controls the MPPTs.
jasebri avatar image
jasebri answered ·

thank you all, so everyone here feels there must be something wrong in the configuration of the installation, right?

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