question

Chris avatar image

Multiplus or Quattro in parallel cascade - How do they operate to cover increasing loads?

Just for the sake of clarity... ( i thought i understood this - but as ever the info is grey or not specific)

Multis or Quattros working in parallel for a larger output capacity. (single phase)

Do the paralleled units mirror each other and operate in the same fashion

or

Is it a cascaded arrangement, where the master is loaded up first, then the second unit starts to come in to cover the load... and so on....?


And then so.....

Shore / generator AC input

Can this be connected to the Master alone , or does it have to connect to each paralleled unit ? (there are schematic examples for both arrangements - ie. two AC sources, but then other information "infers" symetrical connections required.) There is the note about the shore power setting needs dividing by the number of conencted units.


Thanks

Chris

Generatorparallelmultiplus in parallelshorepowercascading inverters
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@Chris

If the wiring is balanced then the loads are shared equally. If not then one will overload vefore the other.

8 Answers
wkirby avatar image
wkirby answered ·

They do operate to share the load equally. 500W each MultiPlus for a 1KW output.
The generator should be connected to both units also with symetrical cabling, as per the diagram in the back of the manual.
Connection to the one master unit is usually employed in a multi phase output configuration where only a single phase suplly is available.

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Chris avatar image
Chris answered ·

ok - great. Didnt confirm that in the basic manual. Ive been fighting to find any of the more system wide schematics.

so.

on to what the LEDs are showing....... none of what i am seeing seems to be covered anywhere.

We have two 5kW Multis (48v) With a heap of Pylon Lithiums. When operaing sub 5kw load, the Masters LEDs illuminate as expected (same as a standalone setup) but, the slave units "Mains ON and Inverter On" LEDs alternate flashing.

When the whole system is loaded up over 5kW, (test was at circa 7.5kW) the slave unit thenalso flashes the Overload LED.

VRM logs the overload event, but the whole system continues to operate fine.

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Chris avatar image
Chris answered ·

In the last hour - i suspect i have found the source of the overload error.

but as ever... its a grey area..lack of detailed documantation, and i am joinging dots with the data i am seeing remotely.

Suspician is the way the Pylon BMU reports charge / discharge current with parallel battery stacks.

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basil katakuzinos avatar image
basil katakuzinos answered ·

Could you show us what your DC Setup looks like.

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Chris avatar image
Chris answered ·

Photo of install:

The Two Pylon batt stacks connect to the left hand Lynx. The loads and generation to the right hand Lynx. Each is fused. Left hand Pylon stack Houses the LV-Hub.
Neil Pavia started a thread on a similar vein in Fabruary.

img-5636.jpgFairly sure that the LV-Hub doesnt report the total stack current (operating or limits)

1631614267903.png

So the GX "thinks" there is a DC overload as the LV-hub only reporting 1/2 of whats really avaiable and is going to each stack, but in actual fact its nowhere near maxed on each stack.


img-5636.jpg (2.0 MiB)
1631614267903.png (43.9 KiB)
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marekp avatar image
marekp answered ·

Hi @Chris

Are you sure that system reports DC overload?

From the picture of you setup I see that DC wires, parallel connected MPs, are not equal lengths.

Sam with the AC wires.

When you load the system with this 7.5kW, take a clamp meter and measure the AC currents on the master and slave separately. The currents should be the same (+/- couple percent). If they are not, you can have a situation when one MP is passing much larger current that the other and you get overload massage.

Same should be on the DC side. Same current going into each MP.


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Chris avatar image
Chris answered ·

Current measurements are bang on identical (well....within 0.05A or so)

Its just Overload flashing on the slave Multi - The source of overload isnt identified.

After some digging... and reading between the lines, i am fairly confident it is the Pylon reporting of the max allowable discharge current to the GX that is the issue.

The Pylon stacks via the Pylon LV-Hub is reporting 125A for 10 battery modules (2x5 in parallel - which follows the Victron info on 25A per US2000 for one stack)

125A x 50v is 6.25kW, and this would closely mirror the overload status...... even though it ran for a good few minutes flashing overload warning ... it wasnt on the AC side..... nothing in the logs either.

This similar behaviour with the LV-Hub is reported at least once by someone else.

Also the reason why there is the difference between the BMV reading and the Pylon - The Pylon LV-Hub doesnt report current currectly for parallled battry stacks.
When i have a minute i'll upload the vid of the "overload" event to Youtube and share the link,.

I am also curious about how "similar" the cable lengths need to be. I can understand if there are metres of difference, the issues. Victron systems are hard enough as it is to make look neat and tidy without extra cable loops to even the lengths out.

Cheers

Chris

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Hi @Chris

Some time ago I asked here about "Overload Warning" I am getting from time to time.

There is no apparent reason for it.

I was told here "don't worry about it because it is only warning" :)

Yesterday I had such warning, and again to apparent reason.

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Chris avatar image
Chris answered ·

ok

Just discovered that the LV-Hub is missing one of the stacks - (only the '1' green LED lit) - so that answers that,.,.....

How best to reset so it hopefully "find" stack 2?

Power cycle by the on . off switch or Press the reset button on the LV-Hub ?

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@Chris

You would need to check the dip switches on the second stack?

And the comms cables.

I think you do have to restart after each stack you add. Sometimes swapping another unit to master helps.