Vehicle operating data were obtained for 30 units of the Altra EV released in 1998 along with actual measured data on their battery deterioration. In roughly a three-year period, these Altra EVs had been driven a combined total of 460,000 miles. The method of estimating battery deterioration was applied to the vehicle operating data collected from the field to estimate battery deterioration, and the results were compared with the measured values.

Figure12: Comparison between capacity deterioration estimated from EV actual driving patterns and actual capacity deterioration measured in the feild

Figure13: Comparison of estimated and measured EV battery deterioration

The estimated and measured data for capacity deterioration are shown in Fig.12. The estimated values agree well with the measured data. Figure 13 presents a graph that compares the estimated and measured deterioration values for each vehicle. The data for all 30 Altra EVs fall within a certain range. This indicates that the method of estimating battery deterioration is also capable of accurately estimating the deterioration of batteries fitted on EVs in the field.

Using the same procedure as for the EV batteries, the method of estimating battery deterioration was used to calculate estimates of power deterioration based on the actual driving pattern models assumed for the Tino HEV. The calculated results are compared in Fig.14 with actual power deterioration data measured in bench durability tests. The estimated power deterioration values agree well with the measured data. This indicates that this method is also suitable for estimating power deterioration.

Figure14: Comparison of power deterioration estimated from HEV actual driving patterns and measured power deterioration

Vehicle operating data for the Tino HEV released in 2000 were obtained along with actual measured data on battery deterioration. The proposed method was applied to those data, in the same way as for the Altra EV, to verify its accuracy in estimating the deterioration of batteries used on HEVs in the field.
Figure 15 shows the power deterioration estimates in comparison with the measured power deterioration of the batteries in use. Good agreement is seen between the estimated and measured power deterioration values. Figure 16 shows a graph that compares the estimated and measured power deterioration data for each vehicle. It is seen that the results for the HEV batteries also fall within a certain range. This confirms that the method of estimating battery deterioration is also capable of estimating with good accuracy the deterioration of batteries fitted on HEVs in real-world use.

Figure15: Comparison of power deterioration estimated from HEV driving patterns and power deterioration measured in the feild

Figure16: Estimated HEV battery power deterioration vs. measured power deterioration

The deterioration of EV and HEV batteries under real-world use can be estimated by converting vehicle operating data to battery load conditions (temperature, number of cycles, storage conditions, etc,), calculating the deterioration rate for each set of conditions and then totaling the results.
The proposed method of estimating battery deterioration provides accurate estimates of both EV battery capacity deterioration and HEV battery power deterioration.
By assuming certain actual driving pattern models for EVs and HEVs, it is possible to make advance estimates of battery deterioration under conditions of real-world vehicle use by applying this method of estimating battery deterioration.