Multiplus II Voltage Sense Error

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schwuppe asked Feb 23, '24

Multiplus II Voltage Sense Error

Hello,

I had sent in my Multiplus II 5000/70-50 for repair but they did not find anything.

After it came back the device is behaving strange and often does not load the battery.

My setup:

The multiplus got the latest firmware version 507. It basically exists to store energy to a battery.
My venus os large installation an raspberry is on v3.20 and now on v3.21.

My battery is a 16S 280Ah system with Seplos BMS v2 10E, connected to the raspberry via RS485. Venus os detects it as SerialBattery(Seplos).

Grid meter is a 3 phase EM24 connected via RS485 to the rasberry.

Solar inverters are AC coupled and not known to the system.

I'm fetching data from Venus OS via MQTT interface.

-I tried with DVCC setting to on and off, since Seplos is not supported by Victron.

-ESS is active in mode Optimized either with or without battery life.

Inverter LEDs are of in the faulty case.

Then I get these entries in the log:

From the manual:

Voltage sense error. The voltage measured at the voltage sense connection deviates too much (more than 7V) from the voltage on the positive and negative connection of the device. There is probably a connection error. The device will remain in normal operation. NOTE: If the "inverter on" LED flashes in phase opposition, this is a VE.Bus error code (see further on).

Do I have to modify some settings? Or is the device defective and how can I make sure?

Multiplus-II error voltage

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Answer 1 · 2024-02-24T14:13:30Z

Alexandra answered · Feb 24 at 02:13 PM

@schwuppe

From what I have read on the forums the Seplos controls the system even when DVCC is off. It bypassed all that. Not sure how true it is since I dont have one.

But in ve config you can disable v sense for diagnostic purposes with the MK3. That seems to solve the issue.

7v is alot though. Probably the worst case I have heard of. Since you have ruled out volt drop over the cable (DMM reading on the terminals compared to the inverters own readings) it seems like a hardware problem.

There is a pre RMA document.

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schwuppe commented · Feb 24 at 02:54 PM

Thanks @Alexandra

What I did also is give MPII full control in the settings and to make sure also disable bus communication from the seplos BMS

After a reset of the venus os I get reproducible these 2 errors:

Masuring the battery termials with a multimeter at the MP gives me around 53V

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Alexandra ♦ schwuppe commented · Feb 24 at 04:34 PM

@schwuppe

Yeah removing the BMS control makes a few things grumpy. You can leave that as it was with control.

What we are trying to establish is if the v sense is the one stopping the battery charging. And if disabled does the system function correctly.

When troubleshooting always choose one thing to change at a time and test.

The low battery though. What are the settings for low battery? Are you running ESS? What are the dynamic cut off set there? Both those settings can trigger that alarm.

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schwuppe Alexandra ♦ commented · Feb 24 at 10:16 PM

Ok after turning off Vsense

and setting Battery monitor to MP-II

and DVCC to off

I do not get the error entries (reproducible immediately before after reset of venus os).

Now ist set back to Battery monitor automatic (Seplos)

and DVCC on

without errors for a while

and it is keeping the power consumption from grid at setpoint. Before it was always turning on and off.

My ESS dynamic cut-offs are at 44.8V. By mistake there was a setting of 48.8V at 2C.

Lets await tomorrow to see how it behaves when inverters turn on.

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Alexandra ♦ schwuppe commented · Feb 26 at 05:11 PM

If you disable v sense you have to keep the battery BMS connected. It needs a source of voltage readings.

The v sense being an issue, if it was me I would return the unit for and RMA and warranty process.

With the Seplos not being fully supported I would expect some things to not be totally right. I have read a lot about Seplos and Victron integration, there are a few incompatible things.

Is the preset lifepo4 ok for the Seplos? I thought they had their own charge voltages different to it?

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schwuppe Alexandra ♦ commented · Feb 28 at 05:02 PM

The defect came with an explosion noise and smoke while I was close to the system. I had my device already sent but they reported back the device is okay after testing it.
Before the defect my system was running without problems and all assembly reports of such a system I've read do not indicate my problems.

Sending it in again in the same state brings the risk that they will not find anything again.

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Alexandra ♦ schwuppe commented · Feb 28 at 05:55 PM

@schwuppe

I would open and do a visual inspection.

You may or may not see anything since components can stop working with no visible signs. But a pop sound suggests there possibly visible signs is possible.

Take photos if you spot it. Still send it in after though

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Answer 2 · 2024-02-25T10:03:56Z

schwuppe answered · Feb 25 at 10:03 AM

Today, after disabling Vsense the system is not workig properly.

-When disconnecting the BMS I got once this:

-ESS optimized with battery life seems to have a negitive effect on turning on battery loading at all, so I set it to optimized without battery life

-Battery SOC is now at 23%, MQTT .. /system/0/Dc/Battery/Soc gives me a value of 95% today

-Now it sometimes loads the battery a bit, most of the time not and never reaches the setpoint. The overall beavior seems random.

-And I got another

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Answer 3 · 2024-02-25T12:29:28Z

nickdb answered · Feb 25 at 12:29 PM

If the system is configured with a BMS and it is unplugged, it will cause these sorts of issues.

Everything here screams a battery/BMS issue of some kind, you would want a shunt if it was disconnected as the system won't do a good job of recording SOC with any accuracy.

Problem or poorly configured DIY/unsupported batteries will cause these sorts of misleading errors and the multi will always bench test fine.

Victron recently updated its third party battery statements for this reason.

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schwuppe commented · Feb 26 at 04:14 PM

Without BMS the battery is a passive element with 16S balanced standard cells. How could this be the reason for a Voltage sense error ?

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Multiplus II Voltage Sense Error

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