question

ewen1980 avatar image
ewen1980 asked

Multiplus Limit?

Im using two MPPT 150/45, a cerbo-gx, a Multiplus 2 48/5000/70-50 and a pylontech battery. When only one MPPT is activ the Multiplus is inverting the full power of the mppt with aproximate 2200W. When the second gets activ the Multiplus caps the inverting at around 3000W. Feed in excess in enabled of course. Limit system feed is not set.

Here are some screenshots from a perfect day:

Both MPPT activ

1688821989783.png


One MPPT activ:1688822024413.pngAnd the other MPPT activ:

1688822211755.png

Multiplus-IIMPPT Controllersfeed-in limit
1688821989783.png (89.3 KiB)
1688822024413.png (83.3 KiB)
1688822211755.png (82.7 KiB)
4 comments
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Alexandra avatar image Alexandra ♦ commented ·
@Ewen1980

What multiplus (model size etc) do you have? we will need more description of your system, you clearly have something else generating power for feedback. It is not coming out of your battery and definitely not from the DC mppts.

is the multiplus in three phase or your system grid metering only in three phase?

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ewen1980 avatar image ewen1980 Alexandra ♦ commented ·

Thanks for the fast reply. Im using a MultiPlus-II 48/5000/70-50 on one phase. I have another Inverter which is feeding in on all three pases.

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mvas avatar image mvas ewen1980 commented ·

It is possible to configure a "Feed-In Limit". Could that field be set to 3000 watts? OR are you limited to 23 amps per phase Feed-In? Given that 5,000 watts = 23 amps x 230 volts. See Amps in Leg #2. I assume this Multiplus is connected to Leg #2 ?

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ewen1980 avatar image ewen1980 mvas commented ·
Thanks for the reply. For debugging i did a reset on the cerbo and configured nothing. I also recognized the connection on l2 and i fixed it to l1. A "Feed-In Limit" is not configured.
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2 Answers
Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

The 5kVA MultiPlus has 4000W cont. output power at 25°C (internal device temperature).
Your battery temperature is at 34°C so I guess the MP is reducing it's output due to the high temperature.

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ewen1980 avatar image ewen1980 commented ·

Thanks for your reply. This sounds correct to limit the output when its hot but the Multiplus should deliver 3700W at 40°C

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nickdb avatar image nickdb ♦♦ ewen1980 commented ·
It is internal temperature. If it is 34C ambient, internal is way above 40C.
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ewen1980 avatar image
ewen1980 answered ·

I disabled my Sungrow inverter and my MPPTs to check the performance of the Multiplus when discharging the battery. Solid 4000W when inverting from Battery but only 3100 from the MPPTs.




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nickdb avatar image nickdb ♦♦ commented ·

According to this image the AC loads are being supplied by grid on L3 and L2 and the battery is feeding back via the inverter to L1 trying to zero out the load or just feeding back. It is supplying 3528W, which is about right for the 3972W pulled from the battery after losses.

So at 3528W the inverter is definitely derated, else it would push more back to the grid.


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ewen1980 avatar image ewen1980 nickdb ♦♦ commented ·

This test should show that the inverter can provide more than just 3100. With both activ MPPTs it does not.

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nickdb avatar image nickdb ♦♦ ewen1980 commented ·
Doesn’t show that. Performance is also affected by altitude.

At 34C ambient and nearer 5000ft AMSL i am lucky to see anywhere near 3000W from that model inverter.

From your battery temps, inverter performance seems right, you just failed to take temperature into your sizing requirements:

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