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Pedro Lima asked

Victron ESS problem with Multiplus II 5000VA

Hi there, we did an installation (VRM id c8df84cacf23), with:

16x REC N-Peak 315w

1x 150/45

1x 250/100

1x Multiplus II 5000VA

BYD-Box 10kWh

70mm2 battery cable (1,5m each)


All the loads are at the AC-Out, as the customer wants backup for everything.

"Off-grid" works perfectly for days, no problem. But with mains connected at the AC-in, there are problems running ESS .

What happens is that randomly (but it seems to happen mostly when loads are about ~2000w with the microwave on). Lighting starts blinking, so appliances go off (TV for example), and everything comes from the grid, then after some seconds the problem stops.

You can check this behavior here for example (customer . made monitoring system) : Out voltage (green line) goes down a lot (actually this is an average, it actually blinks), and it starts taking from the grid (red fill graph). There's no error coming at all.


We checked the wiring, its brand new 3G6mm2, about 10m from to the inverter). Everything works perfectly "off-grid", or with the grid physically bypassing the inverter. With ESS, it turns into a random mess. Yesterday it even gave an overload error at 21:09, with only 2500w load.


Grid voltage is fine, frequency its fine, house runs perfectly with either only grid (bypassing the inverter with a switch), or off-grid, running from the inverter only.

Right now, its running off-grid mode, so it dont damage anything, but if you want I can tell the customer to turn on the grid, so you can check.


We also installed a similar system at the neighbour house (brothers), with a Multiplus II 3000 GX. We tried to mimic the same behavior, but no luck, even with ESS runs flawless.

Charge controller, Venus and Multiplus are all updated to last firmware version (actually it got worst with the last inverter update).


Checked all the wiring, and everything's fine.


Any help please?

Thanks

Multiplus-IIESS
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Pedro Lima avatar image Pedro Lima commented ·

Just to add: We tried to replace the inverter with another Multiplus II 5000, and the behaviour was exactly the same.

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Murray van Graan avatar image Murray van Graan Pedro Lima commented ·

Which gridcode are you using?

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Pedro Lima avatar image Pedro Lima Murray van Graan commented ·

Other type B

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4 Answers
Daniël Boekel (Victron Energy Staff) avatar image
Daniël Boekel (Victron Energy Staff) answered ·

Hi @pedrolima

Did you find the problem yet?
if not: I cannot make much sense of your post, what is the battery voltage during these events?

what is the red line? what is the green filled area?

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Pedro Lima avatar image
Pedro Lima answered ·

So, update.


Victron support told me to tight the some screws inside (!) the Multiplus, that were loose (this is incredible).


Problem got better, but still happens. This is what is happening:

Red line is ACin Voltage, Green on is ACOut voltage.

Green filled graph house consumption (ACout), Red filled graph is mains consumption.


Randomly (mostly with ~2500w loads, specially microwave oven on), inverter goes crazy. It starts to charge from the grid, ACout voltage goes down and its intermitent (lights flicker), and sometimes it even shuts down with a overload!


Any help please?


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Daniël Boekel (Victron Energy Staff) avatar image Daniël Boekel (Victron Energy Staff) ♦♦ commented ·

Hi @pedrolima

What is the name of this site? is it ok if I take a look?

AC-in and AC-out voltage should be the same, as it is a fixed connection in normal / ESS mode where is it measured?

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Pedro Lima answered ·

Hi Daniel, I dont think you understood the problem.

Problem is not that voltage drop. Problem is around 2400w load usually (far from 4000w), it freaks out with the microwave, all the lights start to flicker, some appliances turn off, it starts charging from the grid, etc. It happens randomly, sometimes it happens, sometimes dont.

Off-grid (grid off), works fine, no problem at all !

You can see the behaviour (not completely, as the flickering is too fast to catch on the graphs):


You can see the shutdown here, for no reason, and there was no overload alarm. During one of the freakouts, it shut-off completely:


As it works perfectly "off-grid", sounds like a firmware bug to me.


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Daniël Boekel (Victron Energy Staff) avatar image Daniël Boekel (Victron Energy Staff) ♦♦ commented ·

Hi @pedrolima

When did this happen? I don't see any date.

Remember that in ESS mode, the system actively tries to get the grid setpoint to the configured value, and on load changes it can take seconds to get back to the setpoint, giving fluctuating readings when load changes.

If the unit indeed shuts down when it shouldn't, it should be repaired / replaced.


btw. is the high grid voltage normal there?

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Pedro Lima avatar image Pedro Lima Daniël Boekel (Victron Energy Staff) ♦♦ commented ·

Hi Daniel,

28/09/2019 (you can see the date at the bottom).

Yes, its the second inverter we try, behaviour is exactly the same as the first one.

Thing is that lights flicker a lot, tv set shuts down sometimes, etc! It only happens with ESS, off-grid, or grid only (bypass with a switch), no problem at all.


If it was a hardware fault, shouldnt this problem also show up "off-grid"?


Yes, high grid voltages there.

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Pedro Lima avatar image Pedro Lima Pedro Lima commented ·

Also, see here. I know it takes some time for the ESS to catch up with the loads (seconds), but in this case, it was taking from the grid more than the loads, for several minutes (with lights flickering):


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Pedro Lima answered ·

Here's a video of the lights blinking with ESS on, ~2400w load:

https://www.youtube.com/watch?v=shCxobWncQk&feature=youtu.be

This is serious, I dont think this is the ESS adapting to the load.. happens randomly. Off-grid mode, no problems.

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