Electric Vehicle Speedometer Calibration

val is 100 miles. With a 332lbs passenger or equivalent weight, the vehicle travels 35 miles between any two charging segments.

During this driving test, the values noted include:

• Average vehicle speed • Average distance required between charge • Average distance traveled between charge • Average kWhr available per charge

Driving Range at the End of Day-2 Test

The vehicle driving range test is to determine the maximum driving range achieved at the end of Day-2 during a 12-hour period. The test is repeated with the same passenger weight and minimum range requirements as on Day-1. The same driving test values are noted during the test on Day-2.

Driving Range at the End of Day-3 Test

The test is repeated with the same passenger weight and minimum range requirements as on Days-1 and -2. The same driving test values are noted during the test on Day-3.

ELECTRIC VEHICLE SPEEDOMETER CALIBRATION

In the event the EV speedometer requires recalibration, the vehicle requires a data acquisition system.

The speedometer can be recalibrated using the following steps:

• Record the speedometer reading when the EV is stopped. • Accelerate the EV to 5mph and record the speedometer reading. • Increase the EV speed in increments of 5mph and note the speedometer readings until the final speed of 60mph is achieved. • Increase the EV speed to 80mph and note the speedometer reading. • Develop a speedometer calibration table, taking differences in the speedometer reading and the calculated correction factors into account. • Using this speedometer calibration table, repeat the test with a recalibrated speedometer.

6 ELECTRIC VEHICLE BATTERY

DISCHARGING

The U.S. Advanced Battery Consortium (USABC) has prepared battery test information that provides test guidelines for full-voltage battery packs, battery modules, and battery cells. The test procedures provide procedures and parameter values to be used by all in evaluating the batteries, including the battery developers and other test facilities.

The Variable Power discharge test or the simplified version of the Federal Urban Driving Schedule (FUDS) was developed by the Department of Energy/Electric-Hybrid Vehicle Program (DOE/EHP) Battery Test Task Force (BTTF) in 1988 provides an effective simulation of the dynamic discharge conditions (for driving-cycle testing) in the laboratory. The simplified version profile was modified into the Dynamic Stress Test (DST). The DST is scaled to a percentage of the maximum rated power or USABC power goal, and requires higher regeneration levels than the SFUDS cycle. Table 6–1 summarizes the corresponding power values. The 100% power value is intended to be 80% of the USABC peak power goal for the technology. For example, if this profile is scaled to 80% of 150W/kg, it would have a peak power of 120W/kg.

Commencing with a fully charged battery, the battery is discharged by applying the scaled DST power profile. The 360-second discharge test is repeated with minimal time delay (rest period) between the discharge profiles until the end-of-discharge point specified in the test plan or the battery voltage limit, whichever occurs first, is reached. The end-ofdischarge point is based on the net battery capacity removed (total Ahr-regeneration Ahr). In addition, the DST test provides insight into the VRLA battery’s changing internal resistance simulating the dynamic driving conditions of the electric vehicle (EV).

The DST test simulates the dynamic driving conditions that EV batteries may see.

In addition, to performing these tests at room temperature conditions, effects of temperature may be simulated by maintaining the batteries at several different temperatures including -10°C, 25°C, and 50°C.

Table 6–1 Listing of DST power profile.

Step Duration Cumulated Discharge (secs) Duration (secs) Power (%) 1 16 16 0 2 28 44 -12.5 3 12 56 -25 4 8 64 12.5 5 16 80 0 6 24 104 -12.5 7 12 116 -25 8 8 124 12.5 9 16 140 0 10 24 164 -12.5 11 12 176 -25 12 8 184 12.5 13 16 200 0 14 36 236 -12.5 15 8 244 -100 16 24 268 12.5 17 8 276 25 18 32 308 -25 19 8 316 50 20 44 360 0

In addition, the internal resistance values may be calculated for the I v/s V measurements taken during the DST test from steps 14 and 15. The termination voltage of the DST test is based on a cutoff-point at which the battery voltage reaches 9 volts. As the temperature decreases, the number of DST frames completed before the termination decreases as shown in the figures above and vice versa as the temperature rises, the DST frames completed increases. It may also be noted that the Rint at the second data point (near the 100% SOC) is very close to the Rint (near the 100% DOD).

As the VRLA battery undergoes discharge cycles, its capacity changes with temperature. Although temperature effects on single cells and battery modules are well researched, the performance of several batteries connected together has not been thoroughly researched. In addition to the charging, recharging of battery packs is important to maintain a uniform temperature in the battery pack. Maintaining a uniform temperature is vital both for the battery life and the EV performance. Unfor-