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ajmacleod avatar image
ajmacleod asked

Why didn't my essential loads remain working through grid outage?

Hi, I have a MultiPlus II 24/3000 in an ESS setup with 800WP and 200Ah "drop in" LiFePo4 batteries which has been working well for about six months now. When the grid is lost (either deliberately in testing, or when we've had power cuts) it has always maintained my essential loads (which is my office.)

Yesterday however, we had a thunderstorm and the power was out for about half an hour. This time, power to the essential loads were lost too, for the duration of the power outage. There had been a low battery warning earlier in the afternoon but the voltage seemed well above 24V (above 26V actually) at the time of the outage so I couldn't see why the inverter would fail to power the essential loads?

In addition, there was no "grid lost" alarm, despite the grid having been down for half an hour; when I manually caused grid loss this morning with the AC isolator everything worked as expected and an appropriate alarm was raised. Here are a few graphs from yesterday, showing the power outage from about 19:32 to 20:00 or so:

powercut-ac-input-power.jpg

powercut-essential-loads.jpg

powercut-battery-voltage.jpg

Any ideas?

Multiplus-IIESSgrid parallel
powercut-ac-input-power.jpg (53.3 KiB)
powercut-essential-loads.jpg (57.9 KiB)
powercut-battery-voltage.jpg (72.5 KiB)
9 comments
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seb71 avatar image seb71 commented ·

Not sure what happened, but (if you can) in the future disconnect the grid during thunderstorms.

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ajmacleod avatar image ajmacleod seb71 commented ·
Hi Seb, thanks for the advice and I will try to (it only requires flicking the RCBO in the house after all) however I actually wasn't at home when this one happened...
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seb71 avatar image seb71 ajmacleod commented ·

I actually wasn't at home when this one happened

That's why I mentioned "if you can".

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matt1309 avatar image matt1309 commented ·
A long shot/guessing you've already checked but was there any RCBOs/RCDs tripped on critical load side ie no drawing from grid or battery as critical loads disconnected due to lightening/some other form of earth leakage tripping RCD on critical side?



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ajmacleod avatar image ajmacleod matt1309 commented ·
Hi Matt, nothing had tripped - all my IT stuff had restarted automatically once the power was back. I'm pretty baffled at this point!
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seb71 avatar image seb71 commented ·
Also check the VE.Bus State graph for that period. It might give some clue.
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ajmacleod avatar image ajmacleod seb71 commented ·

powercut-vebus-state.jpgHere's the VE.Bus state... apparently just dropped to "off" during the grid outage

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powercut-vebus-state.jpg (46.4 KiB)
seb71 avatar image seb71 ajmacleod commented ·
So the inverter was off during the relevant period of time.


It turned back on by itself when the grid was back?

Or you had to do something to turn the inverter on?


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ajmacleod avatar image ajmacleod seb71 commented ·
The inverter came back on by itself and was already running again when I got home...
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2 Answers
derrick thomas avatar image
derrick thomas answered ·

You say the batteries are 'drop in'. Are you implying that there is no communication between the batteries and the rest of the system? Or are there coms connected? Reason I ask is because in an ESS system if coms are expected but missing then inverter goes into passthru and if there is a loss of grid the inverter will shut off until power is restored.

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nickdb avatar image
nickdb answered ·

Is anything logged on the GX/VRM under alarms (besides the low voltage you mentioned)?

Can you access the internal BMS of the batteries?

How is the inverter configured? What are the cutoff voltages and ESS dynamic cutoff voltages.

If an inverter turns off and eventually self recovers, without logging relay failures, or other such alarms it is most likely something related to the battery or how the system is set to deal with battery voltage etc.

Drop-ins can be temperamental in series. The BMS may have had a wobble.

You really need to make sure everything is set right, charging and reading correctly.

Without having access, it is a bit challenging to triage this via the internet.

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