The Leaf Spy Pro App has it built-in help description that explains all of its screens very well. It is intimidating, so below I will give you my take on what I feel us most important. I hope the below is not too long,
I think one of the most important Screen is the “Battery Cells” screen. On the top of that screen is the SOH (State Of Health). Note that it varies over time and even on a brand new battery, when I took deliver of my 2024 Leaf SV Plus, it started out at 98.22%.
The BMS (Battery Management System) continually monitors and adjusts SOH and other battery parameters as you drive. Parameters fluctuate can and will fluctuate up and down a bit in the short term. However, The main trend is that SOH goes down over time, as you use up the HV (High Voltage) Battery.
As an example of it going up, after three months of ownership of my 2024, after 1,200 miles. SOH=99.34%.
An example of SOH going down over time as the battery is used up. Is that on my 2023, at trade-on time with 12,915 miles on the odometer, SOH=97.46%, it too started out at 98%.
The BMS parameter estimates fluctuate due to environmental conditions and your driving History. The in-vehicle Battery capacity screen (aka Bars) is showing you an indication of you SOH, without needing Leaf Spy Pro.
The other thing I think is very important is also on the “Battery Cells” page, is that graphically shows you 96 cells groups (pairs in some Leafs). If the cell group bar is Red, that cell group is being actively balanced by the BMS. The mV (millivolt) differential between the lowest cell group voltage and the highest cell group voltage, should be in the low double digits of millivolts. This is the indicator of a good balanced HV battery. When you start to get into the high triple digits it’s an indication that the cell groups are unbalanced and you probably have bad cell(s). This also means you will probably need to, at some point, replace those cells or get a replacement HV battery. .
