Torque Pro on the Kona - overview and setup for interested owners

Certainly SoulEVSpy is convenient for quickly evaluating cell balance with the colour-coding.
I haven't yet bought the non-Lite version to try out the data logging and .csv export.

 

There was a question on FB recently about the definition of a charge/discharge cycle. As most of us know it's defined as a charge and discharge cycle of an energy quantity equal to the rated capacity. Wiki defines it as "... the process of complete charging and discharging". Added to that, a comment from Apple Inc. says: "... a charge cycle means using all the battery's capacity, but not necessarily by discharging it from 100% to 0%...".

So, completing a "cycle" doesn't have to happen from zero to 100% and 100% to zero in one shot. An accumulation of multiple charging and discharging events equalling the rated capacity is still a cycle, as there is nothing implicit as to over what range of SoC those events occur.

When we look at an Li-ion 16850 cell life graph (see below), the lines represent cycles between a number of fixed SoC values aside from the default of zero and 100%, eg. 25 to 75%. Those are plotted against "DST cycles", where they mean 100% cycles. So, the X-values on the 25 to 75 line are the cycle numbers normalised to a defined 100% cycle, i.e. half of that. If the cell life data for 25 to 75 indicates 3,000 "cycles" are available from a particular cell sample at a particular deterioration level (say 90%) then that actually means 6,000 cycles can be acquired when only going using it between 25 and 75%.

We already generally understand as owners that avoiding SoC extremes "can" increase the useful life of the traction battery. "Can" is just being scientifically-conservative or non-committal, I would suggest that the data shows that it most certainly will.

Obviously when you are driving the Kona it's continually discharging and (in much smaller amounts) charging (regen or 'recuperation'). That activity is depreciating the battery life and that is one of the reasons why the BMS records the four data values with titles that start with "Cumulative ...".

There are two primary values measured from the precision current shunt inside the traction battery, one for "cumulative charge current" (CCC) and one for "cumulative discharge current" (CDC). When matched up with the pack voltage at the time of measurement the related values "cumulative energy charge" (CEC) and "cumulative energy discharge" (CED) can be calculated. These numbers will be continually updated in the BMS's memory whenever the car is fully awake, just like odometers. Torque Pro just reads them straight off the BMS and puts them in readable, decimal kWh form.

(In an earlier post in this thread I described a theoretical way that SoC can be calculated from the CEC and CED at any time, provided that the SoC at factory initialisation is known.)

While answering the FB question I realised that you can calculate how many 100% cycles your battery has endured simply by dividing the average of CEC and CED by 64 (kWh). Since these values become much the same over many cycles, you could also make an estimate from either one instead.

Unfortunately both BMS updates zeroed-out all these valuable numbers, but if you happen to have the values recorded before the update(s) you can calculate the cycles from when the car was new by adding them up.

In my case I have data to show that I've used 44 cycles before and 1 cycle subsequent to the updates (in my case all updates were applied 2 weeks ago), so I've used 45 cycles off the battery life at 16,600 km. That number BTW, is related to the efficiency rating so many of us in mild climates would have similar numbers. Those in very cold climates could be as much as double.

If I had charged and driven the car from 100% to zero over those kms I could make a fair assumption that my battery would only be useful for the shortest typical life of a Li-ion battery, perhaps only 400 cycles. If I had confined my usage to say 30 to 70% then I could also fairly assume that I might be able to rely on a much longer life, perhaps 3,000 100% cycles per the graph below.

I'll leave it up to the reader to grab a calculator and figure out how far I could drive in those two scenarios. As a clue if needed, it's (400/45) x 16,600 km and (3,000/45) x 16,600 km. Now, obviously there are other major contributors to battery deterioration to consider, mostly time and temperature, but also frequency of rapid charging to some degree.

Still, these numbers put our SoC considerations in perspective.


This annotated graphic for a single 16850 cell was created from the original copied from batteryuniversity.com