Hello,
I'm wondering for quite a wile now that my battery efficiency seams to be only at around 70%.
By battery efficiency I mean, PV energy to battery vs. energy consumed from battery.
About my Installation:
- 2x MultiPlus 2 48/3000 configured as a 2 phase system
- MPPT 250/70
- MPPT 150/45
- SmartShunt
- DIY Battery 17s EVE 280K (the BMS is not communicating to the Venus OS)
The two MultiPlus and the MPPT 250/70 are wired with 35mm2. The MPPT 150/45 is wired with 16mm2 and the Battery with 70mm2. All cables are 1.5m long. The positive and negative busbars are made of Cu-ETP.
When charging or discharging the battery absolute nothing gets hot or even warm. Not on the busbars, the cables or on the terminals of the cells.
The min. SOC is set to 15% with Battery Life disabled.
For today I exported the kWh xls from the VRM Advanced tab. With this results:
- 2.45 kWh as "PV to battery"
- 1.57 kWh as "Battery to consumers"
Todays charging startet at 13.9%, had it's maximum at 27.1% and discharging ended at 15% SOC.
If I account for the 1.1% SOC which was needed to bring the battery back to 15%, the usable energy which went into the battery was 2.18 kWh vs. 1.57 kWh discharged. That's an efficiency of only 72%
The Multiphase regulation in the ESS settings is set to Total of all phases. My base load is at about 250 W which means 125 W for each MultiPlus.
If we have a look her https://community.victronenergy.com/questions/56351/multiplus-485000-efficiency-curve.html
the discharge efficiency of the 3000 should be 89.7% at 100 W.
If we assume 95% charge and discharge efficiency for LiFePo4 batteries, we would multiply 0.897 (for the Multis at my base load) and 2x 0.95 (charge/discharge for the battery) resulting in 0.809, so an efficiency of almost 81%. Which I was expecting from the system.
So now where do I lose the almost 9%? Or are my assumptions / calculations wrong?
Any helpful input is appreciated.
