SageBrush wrote:lorenfb wrote:So, the only Leaf battery data I concern myself with is Ahrs and battery output impedance (both LeafDD & LeafSpy
calculate), another measure of battery condition over time like with any battery type.
I'd like to hear your opinion:
LeafSpy gives me Ahr and Voltage numbers at the top of my cell voltage histogram. I presume the Ahr is extrapolated out to a full battery, while the voltage appears to be average cell voltage * 96. So e.g from the photo below 384.11*58.15/1000 = 22.33 kWh
If I charge to 100% and calculate the Ahrs*voltage, would that be an accurate kWh capacity of the battery ? I'm inclined to say no because the voltage decreases as the energy is consumed. But lets say that I knew the average battery voltage from 0 - 100% SoC. Could I then calculate an accurate usable kWh capacity ?
Your approach is valid and accurate to evaluate the battery's energy at any point in time or for any SOC.
The battery voltage is nominally about 370 (96 X 3.85 volts) under partial load. The battery voltage drops very little
as the battery's Ahrs availability declines, i.e. reduced SOC, and also as the battery ages. So given that, why not just
be concerned with Ahrs and focus on monitoring that battery parameter exclusive of the nominal battery voltage.
Most likely if one would compare a near new battery with one that had lost 4 -5 bars (6+ years old), the voltage
difference would be less than 5 - 10%, i.e. battery life is all about loss of Ahrs.
One might conclude that your approach is more rigorous than just monitoring Ahrs when evaluating the battery's
condition. Personally, I find it easier when I power-on the Leaf after its overnight charge to immediately determine its
capacity as I begin my daily drive and during my drive. So by quickly knowing the Ahrs and my typical range of about
2 miles/Ahrs, I know the basic condition of the state of the battery when I need to be concerned about getting
to a charging station, if need be, and making it home without reliance on the Leaf's unreliable SOC or GOM.
Note: Your Leaf battery appears to be aging better than mine when it was at your mileage, i.e. mine was 55 Ahrs
and presently at 51 Ahrs @ 51K & 12 bars.