August 20, 20233 yr As many, I read that inverter efficiency is high - above 95% -, MPPT efficiency is given up to 97% but what really these numbers mean ? What is the "efficiency" of a battery that drain few hundreds Wh per day just for floating and running the BMS and what's the charge/discharge ratio ? etc. I run a basic solar station with 4.9 kWc solar panels, a Deye 5K inverter and a 3.5kWh Pylontech battery. Using solarmanpv and home assistant, I can monitor the whole system and I get very surprised when starting to analyzed the data. The losses look so high - about 20 % - that I questioned myself, where did I make the mistake. ==> This post is for discussion about the most accurate way for estimating/measuring the actual system losses. Production comes from solar panels, battery discharge and grid. Consumption concerns loads, battery charging and ... losses. I compute the instant and daily losses in the diagrams using the two variables above. ==> Of course there could be a shift in the daily figure because you can charge the battery one day and discharged it the other day. Losses come from the 4 different converters inside the Deye inverter: Inverter (48V DC to 240V AC) Battery charger (240V AC to 48V DC or 48V DC/DC) 2 MPPT (35-40V DC panels to 48V bus) To be accurate, we could also take into account the consumptions of the controller and the BMS. Considering the internal temperatures : about 50°C for the AC part about 60°C for the DC part ==> The losses per day (2kWh) are not so inconsistent ! Question : how much the efficiency of the converters dependent of the power ? In fact, inverters are not good working at low power such as the 4kWh per day ! An other point concerns the accuracy of the sensors which of course are not high precision sensors and could generate some errors in the measurements. I tried to get more information about the Deye 5K inverter bloc diagrams without real success. I ended with the diagram below where I supposed the sensors are located. (Feel free to comment or add correction to this diagram if needed) As preliminary conclusion, the whole system efficient of 80% does not seem so wrong. AC inverter losses are about 50-60W the 2 MPPT losses are about the same The battery charger does not seem very efficient regarding charge power vs discharge power. Edited August 27, 20233 yr by SDABU
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