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fred48 avatar image
fred48 asked

How to increase the battery discharge on an ESS with MultiPlusII48/500/70


Installation: 3-phase with 3 x MultiPlusII-48-5000-70, Cerbo GX, EM24, ET112, a grid-tied inverter connected to phase L1-ACout1, BYD LVS. All loads connected to L1-, L2-,L3-ACout1. The grid-tied inverter delivers 1,5 kW, 24/7, and is part of a fuel cell system. ESS assistant defined.

Targets: Use ESS to optimize self-consumption peak loads with average consumption appr. 9 - 10 MWh per year, self-generation 13 MWh per year, base load appr. 400 W. Don’t use grid for battery charging. Allow feed-in, if battery is full. Use stored energy to replace grid in case of LOM detection.
Background: Installation location Germany (highest energy price in Europe, peanuts only for feed-in), stable grid,

Commissioning:
EM24 for grid energy (not really necessary), ET112 defined as PV-inverter, separate bi-directional measurement (mode b)

Configuration:
VEConfig3: Load current 7 A (1,5 kW - 400 W = 1,1 kW available for charging; 3 x 7 A x 50 V= 1,1 kW), lithium battery, ESS assistant with LiFePo4 with other type BMS, battery capacity 16 kWh, recommended values for BYD LVS
Cerbo GX set up: BYD LV on CAN-bus, DVCC on, load current limit 20 A, phase compensation, minimum SOC 20 %, shown active limit 50 %, grid set point 1100 W (= 1,5 kW - 400), PV-inverter no set up.

Question:
There is a set up possible according to Cerbo GX manual for limit charge power from AC1. In fact the Cerbo GX set up (2.62) doesn’t offer it. How can I activate it?
It would be useful to have it particularly in Germany, see targets and background.

How can I further optimize self-consumption during peak loads, e.g. increase de-load current of battery, or other actions?

Remark:
The data shown by Cerbo GX console and in VRM portal don’t make sense to me.
Examples: The information about grid, loads, PV-inverter and battery isn’t really balanced apparently PV-power is missing, historical value to grid and production isn’t zero in fact (see attachments).
What can I do to correct?
But one fact is clearly displayed: The minimum effect by the current from the battery.

screenshot-20210218.jpg

I would appreciate everybody’s support very much.

VRM-Report.pdf

cerbo gxESS
vrm-report.pdf (257.3 KiB)
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4 Answers
CristiMV avatar image
CristiMV answered ·

for limiting the charge current I use DVCC option

dvcc.jpg


dvcc.jpg (61.6 KiB)
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fred48 avatar image
fred48 answered ·

Yes, I set 20 A as limit for charge current to avoid charging from grid. I would need a hint by which set up parameters to increase discharge current.


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thomasw-1 avatar image
thomasw-1 answered ·

Hi Fred,
I cannot reproduce, why you want to limit charging current.

  • Battery is only charged, when no AC-loads have to be served.
  • In case of inverter capacity is higher than current AC-consumption, maximum power should be directed to load batteries
  • BYD LVS typically accepts up to 230A, whereas that level is mostly not reached. At the end of charging.phase BYD reduces automatically the current and prevents battery damages.
  • In case you setup such limit, you reach just the opposide, what you desire. In case AC-loads and max-charge current are below PV-production, rest will be fed into grid.

Btw. the highly chosen grid-set-point of 1.100W will also reduce overall PV consumption level. With that setting you force a minimum grid consumption level.

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CristiMV avatar image
CristiMV answered ·

The discharge current (actually power) you set via ESS...maximum inverter power...

1d5e4d60-7dd9-4e95-a8ed-d988fe80fdd6.jpeg


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