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leo9412 avatar image
leo9412 asked

Multiplus Parallel ignores the battery charging voltage

Hello, I have a problem with my Multiplus 2 and Pylontech batteries. I added a second Multiplus 2 to my system a few weeks ago. Now every time I charge to 100% from the battery I get a message that the voltage is too high. The battery reports a charge voltage of 53.2, but it charges to 53.98/99. I've been trying all sorts of settings for days, but the error won't go away. I suspect that the multiplus in the slave mode does not have the correct values from the DVCC or the battery parameters. Has anyone had a similar problem? How can I solve it?

Multiplus-IIESSPylontechDVCC
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6 Answers
Paul B avatar image
Paul B answered ·

as adding a second multiplus doubles your charging power you may find that the batteries cant take that many amps and thus the BMS is reporting a cell overvoltage,

this shows as a high voltage allarm. and thus seems to be that the battery is overvoltage when in fact its really just one cell in the bank is going overvoltage.


have a look in that area and see whats happening

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Paul B avatar image Paul B commented ·
you could limit the MAX charges amps under the dvcc of the Cerbo GX and this may stop it as well, but really look at the cells and see if thats what it is and report it bto the battery maker or check the battery specs
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Alexandra avatar image Alexandra ♦ Paul B commented ·

@leo9412

Have you set the inverters themselves to the recommended 51v and 52v?

And have you just increased you inverters and now don't meet the minimum requirements for bank size?

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Alexandra avatar image Alexandra ♦ Alexandra ♦ commented ·
@leo9412

You can cap voltage in DVCC as well as @Paul B suggestion of charge amps.

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leo9412 avatar image leo9412 Alexandra ♦ commented ·

The DVCC settings have no effect on the Multiplus.

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leo9412 avatar image
leo9412 answered ·

Thank you for your answers. I have 2 MultiPlus-II 48/5000/70-48 and 4 Pylontech US3000.

I've already tried adjusting the settings in the DVCC, but it doesn't seem to have any effect. I have also tried deactivating the chargers on the slave or limiting the maximum charging capacity.

I have already set the recommended settings for the Pylontech with 51 V and 52 V in the Multiplus.

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leo9412 avatar image
leo9412 answered ·

The problem just happened again. The Multiplus charges with over 54v.pylontech.pngpylontech-error.png


pylontech.png (16.4 KiB)
pylontech-error.png (19.8 KiB)
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leo9412 avatar image
leo9412 answered ·

The DC voltage at the inverter

multiplus-error2.png



multiplus-error2.png (20.3 KiB)
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Daniël Boekel (Victron Energy Staff) avatar image
Daniël Boekel (Victron Energy Staff) answered ·

Hi @leo9412

turn on 'Feed excess DC-coupled PV into the grid'

When enabled, if DC bus voltage is higher than the charge voltage, power will be fed to AC to get back to the charge voltage.

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leo9412 avatar image leo9412 commented ·

Thanks for your help. I activated the settings. I always had the settings disabled because I don't have DC solar chargers. I observed today that the problem does not arise when I activate the ESS mode "Keep batteries charged". I'll report tomorrow if it helped.

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Alexandra avatar image Alexandra ♦ leo9412 commented ·
@leo9412

It might be worth sharing what other components you have in the system. Even if they are non victron. Any other charge sources?

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leo9412 avatar image leo9412 Alexandra ♦ commented ·

I only have the Multiplus, Pylontech and the Cerbo GX in the DC system. Between the batteries and Multiplus is a Lynx Distributor and Lynx Power In. At the AC output is a Fronius Primo inverter.

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leo9412 avatar image leo9412 commented ·

@Daniël Boekel (Victron Energy Staff) unfortunately the error happened again.

High voltage alarm by BMS at 53.99v

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leo9412 avatar image
leo9412 answered ·

I exchanged a few more emails with Victron support, the AC wiring should be wrong, the electrician came directly on Monday and made some adjustments, but the battery charging error is still there. Support no longer reports. It's really annoying.

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Alexandra avatar image Alexandra ♦ commented ·

@leo9412

The value under the Pylontec parameters is set by the Pylontec itself. The DVL and CCL and CVL values on the GX are what the Pylon is sending there not what the system is sending to itself.

If you have programmed the inverters and mppts to the 51 and 52v, the battery will be fine.

In DVCC cap the charged voltage to 52V. It may be worth leaving your battery on keep batteries charged for a few days, I suspect you have some kind of cell imbalance.

Alternatively -and i do think this is where the system is having the issue - your Fronius is not being controlled by the system or is not programmed correctly, so it is forcing the battery voltage up.

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leo9412 avatar image leo9412 Alexandra ♦ commented ·

@Alexandra

Thanks, the Fronius automatically throttles when I limit the feed into the grid, so I can't imagine the configuration having a problem, also it worked until the second Multiplus was installed. I found out that the error doesn't happen in "inverter only" mode either. I connected the batteries individually to the Lynx Power In with a cable, should I rather connect them all to one cable? Based on the cell voltage, I suspect that the battery is already partly full, half an hour before the error, the maximum cell voltage is 3.57 and the minimum is 3.42, after that the maximum voltage drops and then charges at a distance of 0.05 from the minimum cell voltage on. When the problem occurs, the maximum cell voltage is 3.62 and the minimum is 3.57.

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Alexandra avatar image Alexandra ♦ leo9412 commented ·

@leo9412

Do you have the correct number of batteries for two inverters?

Try the dvcc voltage cap and see what happens then. Set it to only charge to 90% soc in case of grid faliure.

Individual bus bar is better.

An extra option is to drop the grid charge amps right down on both inverters.

Or a combination of all of the above.

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leo9412 avatar image leo9412 Alexandra ♦ commented ·

@Alexandra

According to the instructions, 4 x Pylontech US2000 with 50Ah per Multiplus 5000 should be used. I have 4 US3000C with 74 Ah and can charge with 37a recommended. I only got the second Multiplus as a peak save, so that my meter doesn't switch off. I can use a total of 7000W at 37A per battery and a maximum of 14000W at 74A. I've limited the Multiplus to 35a, together they should make 70a, like a Multiplus used to be on its own. It would be perfectly fine for me to charge the batteries more slowly, but even further reducing the charge amps doesn't help because the Multiplus doesn't finish at 100%. I could buy 2 or 4 more batteries now, but what if the problem is still there? Nobody gives me the money back. Even the limitation with DVCC doesn't work, as well as the setting in VE.Config. I set 35a per Multiplus but it still charges up to 83a. If the problem does not occur in "Inverter only" and "Keep battery charged" mode, then I suspect a software problem.

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leo9412 avatar image leo9412 leo9412 commented ·

@Alexandra Unfortunately I didn't get an answer from support, can you tell me if I need an external AC meter in parallel mode? Like ET112 or Current Transformer for MultiPlus-II.

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Alexandra avatar image Alexandra ♦ leo9412 commented ·
Do you have 2x multi 2 48/5000?

That is 10 000W of battery power you need at nominal rating.

It wont happen on keep batteries charged because it sinks power to the grid over the battery. And in inverter mode beacuse there is no feedback (during feedback the ccl on the gx from the battery is ignored so it is really important to have the correct minimum or more battery bank there the 1:1 ratio).

The energy meter is more of a local regulation requirement from what I understand adding that can cause other issues as well.

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