question

Christoph Reck avatar image
Christoph Reck asked

ESS efficiency: battery output larger than input?

vrm-2024-02.png

How are the battery values calculated, here are my February data collected as an example:
OK => Consumption:1105 = Grid:346 + Battery:386 + Sun:373.
OK => Solar: 599 = to Battery:218 + Consumption:373 + Grid:7 (1 kWh missing)
OK => Grid: 425 = to Battery:78.5 - Battery:1.2 + Consumption:346

but

Battery input: 296.5 = Grid:78.5 + Solar:218
Battery output: 386
=> Where does that extra 90 kWh come from coming out of a 40 kWh capacity battery?
(90 kWh is more than 65% at the beginning and 20% at the end...).

This makes it impossible to calculate the efficiency and losses of the system.

ess effizienzmesswerte
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3 Answers
Jason - UK avatar image
Jason - UK answered ·

@Christoph Reck Do you have solar panels connected to your batteries via a MPPT unit or is your solar via a solar inverter? A schematic would help with this one as there is a lot of information there.

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Christoph Reck avatar image Christoph Reck commented ·
The panels are connected via the MPPT to the battery, as seen in the diagram below.
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Christoph Reck avatar image
Christoph Reck answered ·

1710539671308.png

I've 9,45 kWp east/west over a Kostal inverter AC-coupled, 2.05 kWp south over a Growatt single phase and 1,4 kWp south-facade over the SmartSolar 150/35 directly to the batteries. Below is the full schematic.
ab17-solar-solarbatterysystem-2023-05-13.png


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nickdb avatar image
nickdb answered ·

Use all 3 tabs to see the full picture. Not just the overview.

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Christoph Reck avatar image Christoph Reck commented ·

Is this what you asked for?
1710628394481.png


1710628449083.png
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What more does this provide to do the simple math of battery in and out to calculate the round-trip efficiency?

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