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SolarMD Data Logger V2 Load Shifting Application


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My Narada 8x200Ah lead acid batteries started showing signs of age after 4 glorious years of flawless backup and cycling. The natural choice in upgrade was lithium and I went for the SolarMD 7.4kWh battery with Data Logger. The Mecer 5KVA inverter is still going strong. It runs the lovely software I got from this forum.


Solar MD Data Logger has several outputs. I have connected the RS232 port on the Mecer to the like port on the Logger. It controls the battery settings on the inverter - sweet. SolarMD supports Voltronics Axpert inverters. I have CANBUS1 on the Logger connected to the SolarMD BMS CANBUS port. The Logger reads the battery through this connection and passes on the settings to the Mecer.


The Data Logger has two dry contact relays which can be programmed either manually or through an expression via the web or direct connection to the Logger using ethernet or as an AP. The data logger is connected to my home network wirelessly and logs data to the MyPower24 site.

I noticed that the battery charges by 11am and releases excess PV and only matches the house load PV. I estimated I was underutilising atleast 5kWh of PV. So I needed to add load. I have 10x Longi 430W monos. A 1.5HP sprinkler pump runs at 10am but for just 45min max. This is where the power of the SolarMD Data Logger comes in. The interface allows the setting of control of the relays by expression:


I wanted to trigger R1 by battery SOC% and to switch it off using PV power level. When the time is between 10:30 and 3pm check if SOC=>95%. If true then switch on R1. To R1 NC I connected Contactor 1 (C1) which is fed by utility power and C2 is fed by Inverter power. Both C1&2 have common output to which I have connected two loads; AC and Geysers. The Geyser line goes through a programmable Timer which ensures that the geysers are on between set time periods. C1 coil is connected to NC port of R1. C2 coil is connected to NO port.


The Load shift works like a charm! The comparison of the PV utilisation graph shows that on 30/09/20 before this loadshift circuit I was underutilising PV (Orange graph) but with load introduced after battery charge I am utilising the PV and the graph is a bell shape (yellow). I am storing excess PV as battery energy and as hot water. The battery energy used to top up when PV is flactuating is replenished after the load is shifted back to utility and the existing excess energy is drawn by the battery. Very impressed with the versatility of the SolarMD Logger.


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On 2020/10/09 at 12:33 PM, Shawn_Mueller said:

Very impressive, Kalito! 


Thanks. Its really working well, I've knocked off around R300 equivalent from my utility bill with this fix. At 10:30am the load shift has happened and the geysers are on and PV is handling this load.


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