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Nicholas Herbst avatar image
Nicholas Herbst asked

Victron MultiPlus II - ESS - Irregular Transfer Time - Appliances switching OFF

Hi All,


Our company has executed over 300 Victron installations and just recently we are encountering a phenomenon where a few systems are not transferring seamlessly from a grid-connected state (ESS) over to the Inverter upon failure of the AC Grid supply.

Configuration:
Victron MultiPlus-II including MultiPlus-II's in parallel
Victron Cerbo GX
Carlo Gavazzi Grid Meter (ET112 or ET340)
Grid code: NRS-097-2-1 (South Africa)
LOM: Enabled (Type B)
Assistant: ESS
Battery: Freedom Won LiTe Home or Pylontech
Firmware: 494, 495, 496, 497

The VRM advanced section does not detect a drop in the AC-Output voltage, however the phenomenon is clearly evident on site where the lights, WiFi router, TV and other plugs will drop and recover - having to reboot as a result of the duration of the power interruption.

We do not have the equipment to measure the output and confirm the transfer time but it is my understanding that the MultiPlus-II is supposed to transfer within 20ms to justify it's proposed UPS rating/capability?

Has anybody got any insights into this problem?


Thanks in advance.


Multiplus-IIESSupstransfer switch
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2 Answers
nickdb avatar image
nickdb answered ·

With eskom issues, often it is the grid browning out. You can try to significantly narrow the cutoff AC voltage for inverting to something nearer 215V or so. That may help.

There have been separate issues with some freedom wons, where the cutover surge causes the battery to dip (effectively not enough battery).

What is the ratio of inverter to battery in these installs? Where it is tight, or above recommendations, often coupled with lower SOC's, then this has become fairly common in SA.

Usually the recommended battery sizing has not been followed.

Perhaps some more info?

Can be various causes, most common - not enough battery.

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Nicholas Herbst avatar image Nicholas Herbst commented ·
The one affected system has 2 x Freedom Won LiTe Home 20/16 batteries on a parallel MultiPlus-II 5kVA system (10kVA) - so certainly not a "fringe" case with regards to battery capacity pairing to inverter capacity.


We have tried changing the grid code to "other", and then adjusting the acceptable incoming voltage range to a very narrow range (215V -245V) but without remedy of the issue.

We'd like to trial disabling the LOM detection, albeit the system will then become very non-compliant (to the best of our understanding).

I think we need Victron Energy to take a closer look at this problem, as the UPS transfer time is a critical feature/function.

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Nicholas Herbst avatar image
Nicholas Herbst answered ·

@Guy Stewart (Victron Community Manager) & @Daniël Boekel (Victron Energy Staff)

Do you have any thoughts or insights into this problem?

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mike-moody avatar image mike-moody commented ·
Hi Nicholas

Have you found any solution to this yet as I have ( and others ) same issues...

I recall some comments about using a contactor to immediately cut mains live / neutral on the start of load shedding with the neutral voltage dip.....

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