Had my first grid reconnect event of the season since April 28th and a small thing went wrong
BEFORE the inverter could switch to grid (Set for 38.4v), the Jack-In-The-Box (JITB) battery controller disconnected (at 38.7v) and shut the inverter down entirely around 3AM. I woke up around 4AM and sensed something was wrong as the nightlights were out
the issue was that the variance between cells is set to 0.200v, if the difference between the high and low cells is that or greater, the JITB disconnects to ensures no single cell goes below 3.00v, which would damage the cell. I think the most recent modules I acquired and added have some weaknesses at low voltage.
View attachment 68189View attachment 68190
I had to set the variance to 0.300v in order to stabilize it long enough to do more diagnosis.
As can be seen, it is not properly bottom balanced. As the grid powered the house from 4AM to around 10AM, the system did some balancing.
I will be setting the inverter's Low Battery Transfer to grid voltage to 39.0v, up from 38.4 to stay above that problem area.
36.0v is totally dead, the JITB has a pack voltage of 37.0v as a final disconnect safety limit, along with the variance disconnect trigger.
If the modules were more equal, then I could utilize a lower Low Battery Transfer voltage of 38 or the 38.4 I had it at.
So consider a mix of usedbatteries, I guess I will bump to the 39.0v
As my goal is to add more modules to be able to have a larger battery reserve I aim to keep the battery voltage at 45v or higher most of the time.
This set of 40wkh lasted a little over 2 days of heavy cloud cover and rain, as it steadily declined from 48v to 38.8v over that time
I roughly deduce 20kwh provides me a single day of storage. My goal of 5 days seems to be satisfied with a bank of 100kwh. I can support 110kwh in space and interconnects