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kc27 asked

Round Trip Efficiency

I have 3 x Multiplus II 48/3000 with 2 x 16 x 280 Ah LiFePO4.
I use this only as a ESS for buying in hours when the electricity is cheap (and then charge the cells) en sale in hours when prices are high (and then discharge the cells).
I stay within the healthy ranges of my cells (SOC >= 15% and SOC <=95%)

My average load is 4,5 kW for charge and discharge (every Multiplus takes 1,5 kW)

During charging the battery current is about 38 A, during discharge about -48 A.

I have calculated my AC round trip efficiency(RTE) in the month december 2022:

  • import from grid: 608 kWh
  • export to grid: 474 kWh
  • RTE = 474/608 = 78%

Import and export quantities are measured by Multiplus/gx (grid meter is still in backorder)

My questions are:

  • is 78% a normal quantity (I hoped this was 85%)?
  • if not: where should I look for errors and mistakes in my configuration to improve my efficiency?

Thanks in advance!

Multiplus-IIgrid parallel
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Rob Duthie avatar image Rob Duthie commented ·
Hi


Be about right at 80% if the 3x inverters are in parallel the losses are much greater, Also the internal meters are not that accurate.

Also it depends on the PF of the loads can make difference.

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shaneyake answered ·

Your RTE sounds about right to me.
90% AC to DC and DC to AC is what I see on average.
97% for the battery.
So 100*0.90*0.97*0.9 = 78.57% RTE

The actual watt reading from the CT's in the multiplus aren't great but the kwh readings over time aren't normally that far off. Normally a percent or 2 off in my experience but Meter will be much better.

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Related Resources

MultiPlus-II Product page 

MultiPlus-II Manual

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