Recently there seems to be members that question whether their HVB is "OK" as they watch the battery symbol and believe that the HBV isn't performing as it should. I have suggested many times to get ForScan and record data. Then, after the fact one can look at the data and assess how their HBV is performing. I understand that everyone may not have the knowledge or excel skills to do the analysis but IMO, this is the only way one can determine how their car is performing. The dealer will be no help.
One simply needs to record three PIDs with ForScan:
BATT_CHAR [SOC] (%)
One then computes the energy going into and out of the HVB. The BECM also does this ("columb counting"). Once the ForScan data is uploaded into Excel, the volts are multiplied by the Amps and multiplied by the change in time between time stamps. Typically with my ELM327 I will see about 25+ scans per second which would be 25 rows of excel data per second of recording. So, if the volts are 250 V and the current is 100 A and the difference in time stamps on two successive rows is 40 msec (1/25), then the energy out of the HVB would be 1000 Wsec. If the next 39 time stamp intervals were the same volts and current, then the total energy out of the HVB would be 40,000 Wsec. So, one simply acciumulates the energy flow for each time stamp period. The cumulative energy in the HVB will decrease (SOC decreases) for positive Amps out of the HVB and increases (SOC increases) for power flow into the HVB (PID shows negative current).
The first chart shows the SOC and accumulted energy flow (kWh) over about 150000 scans, about 6000 plus seconds (over 1 hour and 40 minutes) of driving 75-78 mph on I17 between Flagstaff and Phoenix - downhill about 6000 ft. So, the largest change is kWh is 0.514 kWh between about 1291 and 2916 seconds. The SOC went from 34.2% to 70.7%. A change of 36.5% in SOC represents 0.514 kWh. 0.514 kWh divided by 36.5% = 1.397 kWh -- the energy capacity of the HVB. Pretty close to 1.4 kWh. You can pick other points on the graph and do the same calculations.
The second chart shows the error in the estimated SOC of the HVB based on the "columb counting" and the PID SOC. As one can see assuming 1.4 kWh HVB capacity, the estimated SOC never exceeds 0.35% difference. Over the total time period the difference (error) is virtually zero from start to finish.
I don't know how much HVB capacity I have lost but the Ford algorithms continue to allow full use of around a 30% to 70% range of the initial 1.4 kWh of range. Idaho National Lab shows their test vehicles lost around 6% of capacity at about 105,000 miles (my current mileage). I'm going to continue to analyze the data I collected and will post voltage vs SOC curves trying to see where the knee of the HVB discharge curve might be. With 150,000 data point, I can segregate the data based on discharge rate and develop a series of curves and compare against INL test data.
I still believe that we have little to worry about with respect to HBV longevity in our C-Max Hybrid. To this date I know of no one that has had a HVB capacity issue. In fact, several members have over 200k miles and still get great FE. Paul (ptjones) you need to keep that baby going so we can see how far the HVB will go. ICE may need major work before the HVB.
BTW, I need a faster PC. I have my sons 6 year old gaming desktop. It's still fast but running spreadsheets with 150,000 rows and 10 columns takes several seconds to complete. But the graphs are the real time consumming functions - minutes sometimes especially curve fits.
SOC PIP vs Integrated kW.JPG 85.76KB 0 downloads
SOC PID vs Calc SOC.JPG 72.14KB 0 downloads
Edited by Plus 3 Golfer, 29 November 2018 - 09:46 AM.