Having installed an Economy 7 (2 import and one export tariff) meter I arranged for an additional 3.6kWh Dyness battery to be added to my existing two battery array. Here's the day of the install:
The irregular State Of Charge % trace bothered me but I thought it might take some time for the batteries to "balance". Anyway, I got up in the middle of the night when the inverter was due to draw cheap electricity from the grid and this is what I found:
At around 1AM, when the inverter started its battery charging cycle, the load changed from around 0.2kW to around 1.4kW. Something was very wrong. After researching the configuration of the battery stack, I discovered that the installer had configured them as 2 Master units and 1 Slave unit instead of 1 Master and 2 Slave units. This I fixed.
I dread to think of the consequences if this error had gone unchecked. Could the inverter or batteries have been irreparably damaged? Would there have been a significant financial penalty? I've resolved to always check what the "professionals" have done to the best of my ability. 0 for 2 (in American parlance) isn't very reassuring.