Section 600.116-12 - Special procedures related to electric vehicles and hybrid electric vehicles(a) Determine fuel economy values for electric vehicles as specified in §§ 600.210 and 600.311 using the procedures of SAE J1634 (incorporated by reference in § 600.011 ). Use the procedures of SAE J1634, Section 8, with the following clarifications and modifications for using this and other sections of SAE J1634: (1) Vehicles that cannot complete the Multi-Cycle Range and Energy Consumption Test (MCT) because they are unable travel the distance required to complete the test with a fully charged battery, or they are unable to achieve the maximum speed on either the UDDS or HFEDS (Highway Fuel Economy Drive Cycle also known as the HFET) cycle should seek Administrator approval to use the procedures outlined in SAE J1634 Section 7 Single Cycle Range and Energy Consumption Test (SCT).(2) The MCT includes the following key-on soak times and key-off soak periods:(i) As noted in SAE J1634 Section 8.3.4 , a 15 second key-on pause is required between UDDS1 and HFEDS1, and UDDS3 and HFEDS2.(ii) As noted in SAE J1634 Section 8.3.4 , a 10-minute key-off soak period is required between HFEDS1 and UDDS2, and HFEDS2 and UDDS4.(iii) A key-off soak period up to 30 minutes may be inserted between UDDS2 and the first phase of the mid-test constant speed cycle, between UDDS4 and the first phase of the end-of-test constant speed cycle, and between the end of the mid-test constant speed cycle and UDDS3. Start the next test segment immediately if there is no key-off soak between test segments.(iv) If multiple phases are required during either the mid-test constant speed cycle or the end-of-test constant speed cycle there must be a 5-minute to 30-minute key-off soak period between each constant speed phase as noted in SAE J1634 Section 6.6 .(3) As noted in SAE J1634 Section 8.3.4 , during all `key-off' soak periods, the key or power switch must be in the "off" position, the hood must be closed, the test cell fan(s) must be off, and the brake pedal not depressed. For vehicles which do not have a key or power switch the vehicle must be placed in the `mode' the manufacturer recommends when the vehicle is to be parked and the occupants exit the vehicle.(4) Manufacturers may determine the mid-test constant speed cycle distance (dM) using their own methodology and good engineering judgment. Otherwise, either Method 1 or Method 2 described in Appendix A of SAE J1634 may be used to estimate the mid-test constant speed cycle distance (dM). The mid-test constant speed cycle distance calculation needs to be performed prior to beginning the test and should not use data from the test being performed. If Method 2 is used, multiply the result determined by the Method 2 equation by 0.8 to determine the mid-test constant speed cycle distance (dM).(5) Divide the mid-test constant speed cycle distance (dM) by 65 mph to determine the total time required for the mid-test constant speed cycle. If the time required is one hour or less, the mid-test constant speed cycle can be performed with no key-off soak periods. If the time required is greater than one hour, the mid-test constant speed cycle must be separated into phases such that no phase exceeds more than one hour. At the conclusion of each mid-test constant speed phase, except at the conclusion of the mid-test constant speed cycle, perform a 5-minute to 30-minute key-off soak. A key-off soak period up to 30 minutes may be inserted between the end of the mid-test constant speed cycle and UDDS3.(6) Using good engineering judgment determine the end-of-test constant speed cycle distance so that it does not exceed 20% of the total distance driven during the MCT as described in SAE J1634 Section 8.3.3 .(7) Divide the end-of-test constant speed cycle distance (dE) by 65 mph to determine the total time required for the end-of-test constant speed cycle. If the time required is one-hour or less the end-of-test constant speed cycle can be performed with no key-off soak periods. If the time required is greater than one-hour the end-of-test constant speed cycle must be separated into phases such that no phase exceeds more than one-hour. At the conclusion of each end-of-test constant speed phase, perform a 5-minute to 30-minute key-off soak.(8) SAE J1634 Section 3.13 defines useable battery energy (UBE) as the total DC discharge energy (Edctotal), measured in DC watt-hours for a full discharge test. The total DC discharge energy is the sum of all measured phases of a test inclusive of all drive cycle types. As key-off soak periods are not considered part of the test phase, the discharge energy that occurs during the key-off soak periods is not included in the useable battery energy.(9) Recharging the vehicle's battery must start within three hours after the end of testing.(10) At the request of a manufacturer, the Administrator may approve the use of an earlier version of SAE J1634 when a manufacturer is carrying over data for vehicles tested using a prior version of SAE J1634.(11) All label values related to fuel economy, energy consumption, and range must be based on 5-cycle testing or on values adjusted to be equivalent to 5-cycle results. Prior to performing testing to generate a 5-cycle adjustment factor, manufacturers must request Administrator approval to use SAE J1634 Appendices B and C for determining a 5-cycle adjustment factor with the following modifications, clarifications, and attestations:(i) Before model year 2025, prior to performing the 20 °F charge-depleting UDDS, the vehicle must soak for a minimum of 12 hours and a maximum of 36 hours at a temperature of 20 °F. Prior to beginning the 12 to 36 hour cold soak at 20 °F the vehicle must be fully charged, the charging can take place at test laboratory ambient temperatures (68 to 86 °F) or at 20 °F. During the 12 to 36 hour cold soak period the vehicle may not be connected to a charger nor is the vehicle cabin or battery to be preconditioned during the 20 °F soak period.(ii) Beginning with model year 2025, the 20 °F UDDS charge-depleting UDDS test will be replaced with a 20 °F UDDS test consisting of two UDDS cycles performed with a 10-minute key-off soak between the two UDDS cycles. The data from the two UDDS cycles will be used to calculate the five-cycle adjustment factor, instead of using the results from the entire charge-depleting data set. Manufacturers that have submitted and used the average data from 20 °F charge-depleting UDDS data sets will be required to revise their 5-cycle adjustment factor calculation and re-label vehicles using the data from the first two UDDS cycles only. Manufacturers, at their discretion, would also be allowed to re-run the 20 °F UDDS test with the battery charged to a state-of-charge (SoC) determined by the manufacturer. The battery does not need to be at 100% SoC before the 20 °F cold soak.(iii) Manufacturers must submit a written attestation to the Administrator at the completion of testing with the following information:(A) A statement noting the SoC level of the rechargeable energy storage system (RESS) prior to beginning the 20 °F cold soak for testing performed beginning with model year 2025.(B) A statement confirming the vehicle was not charged or preconditioned during the 12 to 36 hour 20 °F soak period before starting the 20 °F UDDS cycle.(C) A summary of all the 5-cycle test results and the calculations used to generate the 5-cycle adjustment factor, including all the 20 °F UDDS cycles, the distance travelled during each UDDS and the measured DC discharge energy during each UDDS phase. Beginning in model year 2025, the 20 °F UDDS test results will consist of only two UDDS cycles.(D) Beginning in model year 2025, calculate City Fuel Economy using the following equation for RunningFC instead of the equation on Page 30 in Appendix C of SAE J1634: View Image
(E) A description of each test group and configuration which will use the 5-cycle adjustment factor, including the battery capacity of the vehicle used to generate the 5-cycle adjustment factor and the battery capacity of all the configurations to which it will be applied.(iv) At the conclusion of the manufacturers testing and after receiving the attestations from the manufacturer regarding the performance of the 20 °F UDDS test processes, the 5-cycle test results, and the summary of vehicles to which the manufacturer proposes applying the 5-cycle adjustment factor, the Administrator will review the submittals and inform the manufacturer in writing if the Administrator concurs with the manufacturer's proposal. If not, the Administrator will describe the rationale to the manufacturer for not approving their request.(b) Determine performance values for hybrid electric vehicles that have no plug-in capability as specified in §§ 600.210 and 600.311 using the procedures for charge-sustaining operation from SAE J1711 (incorporated by reference in § 600.011 ). We may approve alternate measurement procedures with respect to these vehicles if that is necessary or appropriate for meeting the objectives of this part. For example, we may approve alternate Net Energy Change/Fuel Ratio tolerances for charge-sustaining operation as described in paragraph (c)(5) of this section.(c) Determine performance values for hybrid electric vehicles that have plug-in capability as specified in §§ 600.210 and 600.311 using the procedures of SAE J1711 (incorporated by reference in § 600.011 ), with the following clarifications and modifications: (1) To determine CREE values to demonstrate compliance with GHG standards, calculate composite values representing combined operation during charge-depleting and charge-sustaining operation using the following utility factors, except as otherwise specified in this paragraph (c): Table 1 to Paragraph (c)(1) -Fleet Utility Factors for Urban "City" Driving
| Schedule range for UDDS phases, miles | Model year 2030 and earlier | Model year 2031 and later |
| Cumulative UF | Sequential UF | Cumulative UF | Sequential UF |
| 3.59 | 0.125 | 0.125 | 0.062 | 0.062 |
| 7.45 | 0.243 | 0.117 | 0.125 | 0.062 |
| 11.04 | 0.338 | 0.095 | 0.178 | 0.054 |
| 14.90 | 0.426 | 0.088 | 0.232 | 0.053 |
| 18.49 | 0.497 | 0.071 | 0.278 | 0.046 |
| 22.35 | 0.563 | 0.066 | 0.324 | 0.046 |
| 25.94 | 0.616 | 0.053 | 0.363 | 0.040 |
| 29.80 | 0.666 | 0.049 | 0.403 | 0.040 |
| 33.39 | 0.705 | 0.040 | 0.437 | 0.034 |
| 37.25 | 0.742 | 0.037 | 0.471 | 0.034 |
| 40.84 | 0.772 | 0.030 | 0.500 | 0.029 |
| 44.70 | 0.800 | 0.028 | 0.530 | 0.029 |
| 48.29 | 0.822 | 0.022 | 0.555 | 0.025 |
| 52.15 | 0.843 | 0.021 | 0.580 | 0.025 |
| 55.74 | 0.859 | 0.017 | 0.602 | 0.022 |
| 59.60 | 0.875 | 0.016 | 0.624 | 0.022 |
| 63.19 | 0.888 | 0.013 | 0.643 | 0.019 |
| 67.05 | 0.900 | 0.012 | 0.662 | 0.019 |
| 70.64 | 0.909 | 0.010 | 0.679 | 0.017 |
Table 2 to paragraph (c)(1) -Fleet Utility Factors for Highway Driving
| Schedule range for HFET, miles | Model year 2030 and earlier | Model year 2031 and later |
| Cumulative UF | Sequential UF | Cumulative UF | Sequential UF |
| 10.3 | 0.123 | 0.123 | 0.168 | 0.168 |
| 20.6 | 0.240 | 0.117 | 0.303 | 0.136 |
| 30.9 | 0.345 | 0.105 | 0.414 | 0.110 |
| 41.2 | 0.437 | 0.092 | 0.503 | 0.090 |
| 51.5 | 0.516 | 0.079 | 0.576 | 0.073 |
| 61.8 | 0.583 | 0.067 | 0.636 | 0.060 |
| 72.1 | 0.639 | 0.056 | 0.685 | 0.049 |
(2) Determine fuel economy values to demonstrate compliance with CAFE standards as follows: (i) For vehicles that are not dual fueled automobiles, determine fuel economy using the utility factors specified in paragraph (c)(1) of this section for model year 2030 and earlier vehicles. Do not use the petroleum-equivalence factors described in 10 CFR 474.3 .(ii) Except as described in paragraph (c)(2)(iii) of this section, determine fuel economy for dual fueled automobiles from the following equation, separately for city and highway driving: EQUATION 2 TO PARAGRAPH (C)(2)(II)
View Image
Where:
MPGgas = The miles per gallon measured while operating on gasoline during charge-sustaining operation as determined using the procedures of SAE J1711.
MPGeelec = The miles per gallon equivalent measured while operating on electricity. Calculate this value by dividing the equivalent all-electric range determined from the equation in § 86.1866-12(b)(2)(ii) by the corresponding measured Watt-hours of energy consumed; apply the appropriate petroleum-equivalence factor from 10 CFR 474.3 to convert Watt-hours to gallons equivalent. Note that if vehicles use no gasoline during charge-depleting operation, MPGeelec is the same as the charge-depleting fuel economy specified in SAE J1711.
(iii) For 2016 and later model year dual fueled automobiles, you may determine fuel economy based on the following equation, separately for city and highway driving: EQUATION 3 TO PARAGRAPH (C)(2)(III)
View Image
Where:
UF = The appropriate utility factor for city or highway driving specified in paragraph (c)(1) of this section for model year 2030 and earlier vehicles.
(3) To determine fuel economy and CO2 emission values for labeling purposes, calculate composite values representing combined operation during charge-depleting and charge-sustaining operation using the following utility factors except as specified in this paragraph (c): Table 3 of § 600.116-12 -Multi-Day Individual Utility Factors for Urban "City" Driving
| Schedule range for UDDS phases, miles | Equivalent 5-cycle distance, miles | Cumulative
UF | Sequential
UF |
| 3.59 | 2.51 | 0.08 | 0.08 |
| 7.45 | 5.22 | 0.15 | 0.08 |
| 11.04 | 7.73 | 0.22 | 0.06 |
| 14.90 | 10.43 | 0.28 | 0.06 |
| 18.49 | 12.94 | 0.33 | 0.05 |
| 22.35 | 15.65 | 0.38 | 0.05 |
| 25.94 | 18.16 | 0.43 | 0.04 |
| 29.80 | 20.86 | 0.47 | 0.04 |
| 33.39 | 23.37 | 0.50 | 0.04 |
| 37.25 | 26.08 | 0.54 | 0.04 |
| 40.84 | 28.59 | 0.57 | 0.03 |
| 44.70 | 31.29 | 0.60 | 0.03 |
| 48.29 | 33.80 | 0.62 | 0.02 |
| 52.15 | 36.51 | 0.65 | 0.02 |
| 55.74 | 39.02 | 0.67 | 0.02 |
| 59.60 | 41.72 | 0.69 | 0.02 |
| 63.19 | 44.23 | 0.71 | 0.02 |
| 67.05 | 46.94 | 0.72 | 0.02 |
| 70.64 | 49.45 | 0.74 | 0.01 |
| 74.50 | 52.15 | 0.75 | 0.01 |
| 78.09 | 54.66 | 0.78 | 0.03 |
| 81.95 | 57.37 | 0.79 | 0.01 |
| 85.54 | 59.88 | 0.80 | 0.01 |
| 89.40 | 62.58 | 0.81 | 0.01 |
| 92.99 | 65.09 | 0.82 | 0.01 |
Table 4 of § 600.116-12 -Multi-Day Individual Utility Factors for Highway Driving
| Schedule range for HFET phases, miles | Equivalent 5-cycle distance, miles | Cumulative
UF | Sequential
UF |
| 10.30 | 7.21 | 0.21 | 0.21 |
| 20.60 | 14.42 | 0.36 | 0.16 |
| 30.90 | 21.63 | 0.48 | 0.12 |
| 41.20 | 28.84 | 0.57 | 0.09 |
| 51.50 | 36.05 | 0.64 | 0.07 |
| 61.80 | 43.26 | 0.70 | 0.06 |
| 72.10 | 50.47 | 0.75 | 0.04 |
| 82.40 | 57.68 | 0.78 | 0.04 |
| 92.70 | 64.89 | 0.81 | 0.03 |
| 103.00 | 72.10 | 0.83 | 0.02 |
| 113.30 | 79.31 | 0.85 | 0.02 |
(4) You may calculate performance values under paragraphs (c)(1) through (3) of this section by combining phases during FTP testing. For example, you may treat the first 7.45 miles as a single phase by adding the individual utility factors for that portion of driving and assigning emission levels to the combined phase. Do this consistently throughout a test run.(5) Instead of the utility factors specified in paragraphs (c)(1) through (3) of this section, calculate utility factors using the following equation for vehicles whose maximum speed is less than the maximum speed specified in the driving schedule, where the vehicle's maximum speed is determined, to the nearest 0.1 mph, from observing the highest speed over the first duty cycle (FTP, HFET, etc.): EQUATION 4 TO PARAGRAPH (C)(5)
View Image
Where:
UFi = the utility factor for phase i. Let UF0 = 0.
j = a counter to identify the appropriate term in the summation (with terms numbered consecutively).
k = the number of terms in the equation (see Table 5 of this section).
di = the distance driven in phase i.
ND = the normalized distance. Use 399 for both FTP and HFET operation for CAFE and GHG fleet values, except that ND = 583 for both FTP and HFET operation for GHG fleet values starting in model year 2031. Use 399 for both FTP and HFET operation for multi-day individual values for labeling.
Cj = the coefficient for term j from the following table:
Table 5 to Paragraph (c)(5) -City/Highway Specific Utility Factor Coefficients
| j | Fleet values for CAFE for all model years, and for GHG through MY 2030 | Fleet values for GHG starting in MY 2031 | Multi-day individual values for labeling |
| City | Highway | City or highway | City or highway |
| 1 | 14.86 | 4.8 | 10.52 | 13.1 |
| 2 | 2.965 | 13 | -7.282 | -18.7 |
| 3 | -84.05 | -65 | -26.37 | 5.22 |
| 4 | 153.7 | 120 | 79.08 | 8.15 |
| 5 | -43.59 | -100.00 | -77.36 | 3.53 |
| 6 | -96.94 | 31.00 | 26.07 | -1.34 |
| 7 | 14.47 | | | -4.01 |
| 8 | 91.70 | | | -3.90 |
| 9 | -46.36 | | | -1.15 |
| 10 | | | | 3.88 |
n = the number of test phases (or bag measurements) before the vehicle reaches the end-of-test criterion.
(6) Determine End-of-Test as follows:(i) Base End-of-Test on a 2 percent State of Charge as specified in Section 3.5.1 of SAE J1711.(ii) Base End-of-Test on a 1 percent Net Energy Change/Fuel Ratio as specified in Section 3.5.2 of SAE J1711.(iii) For charge-sustaining tests, we may approve alternate Net Energy Change/Fuel Ratio tolerances as specified in Appendix C of SAE J1711 to correct final fuel economy values, CO2 emissions, and carbon-related exhaust emissions. For charge-sustaining tests, do not use alternate Net Energy Change/Fuel Ratio tolerances to correct emissions of criteria pollutants. Additionally, if we approve an alternate End-of-Test criterion or Net Energy Change/Fuel Ratio tolerances for a specific vehicle, we may use the alternate criterion or tolerances for any testing we conduct on that vehicle.(7) Use the vehicle's Actual Charge-Depleting Range, Rcda, as specified in Section 7.1.4 of SAE J1711 for evaluating the end-of-test criterion.(8) Measure and record AC watt-hours throughout the recharging procedure. Position the measurement appropriately to account for any losses in the charging system.(9) We may approve alternate measurement procedures with respect to plug-in hybrid electric vehicles if they are necessary or appropriate for meeting the objectives of this part.(10) The utility factors described in this paragraph (c) and in § 600.510 are derived from equations in SAE J2841. You may alternatively calculate utility factors from the corresponding equations in SAE J2841 as follows: (i) Calculate utility factors for labeling directly from the equation in SAE J2841 Section 6.2 using the Table 2 MDIUF Fit Coefficients (C1 through C10) and a normalized distance (norm_dist) of 399 miles.(ii) Calculate utility factors for fuel economy standards from the equation in SAE J2841 Section 6.2 using the Table 5 Fit Coefficients for city/Hwy Specific FUF curves weighted 55 percent city, 45 percent highway and a normalized distance (norm_dist) of 399 miles.(iii) Starting in model year 2031, calculate utility factors for GHG compliance with emission standards from the equation in SAE J2841 Section 6.2 using the Table 2 FUF Fit Coefficients (C1 through C6) and a normalized distance (norm_dist) of 583 miles. For model year 2026 and earlier, calculate utility factors for compliance with GHG emission standards as described in paragraph (c)(10)(ii) of this section.(11) The following methodology is used to determine the usable battery energy (UBE) for a PHEV using data obtained during either the UDDS Full Charge Test (FCT) or the HFET FCT as described in SAE J1711:(i) Perform the measurements described in SAE J1711 Section 5.1.3.d. Record initial and final SOC of the RESS for each cycle in the FCT.(ii) Perform the measurements described in SAE J1711 Section 5.1.3.c. Continuously measure the voltage of the RESS throughout the entire cycle, or record initial and final voltage measurements of the RESS for each test cycle.(iii) Determine average voltage of the RESS during each FCT cycle by averaging the results of the continuous voltage measurement or by determining the average of the initial and final voltage measurement.(iv) Determine the DC discharge energy for each cycle of the FCT by multiplying the change in SOC of each cycle by the average voltage for the cycle.(v) Instead of independently measuring current and voltage and calculating the resulting DC discharge energy, you may use a DC wideband Watt-hour meter (power analyzer) to directly measure the DC discharge energy of the RESS during each cycle of the FCT. The meter used for this measurement must meet the requirements in SAE J1711 Section 4.4.(vi) After completing the FCT, determine the cycles comprising the Charge-Depleting Cycle Range (Rcdc) as described in SAE J1711 Section 3.1.14. Charge-sustaining cycles are not included in the Rcdc. Rcdc includes any number of transitional cycles where the vehicle may have operated in both charge-depleting and charge-sustaining modes.(vii) Determine the UBE of the PHEV by summing the measured DC discharge energy for each cycle comprising Rcdc. Following the charge-depleting cycles and during the transition to charge-sustaining operation, one or more of the transition cycles may result in negative DC discharge energy measurements that result from the vehicle charging and not discharging the RESS. Include these negative discharge results in the summation. (d)Determining the proportion of recovered energy for hybrid electric vehicles. Testing of hybrid electric vehicles under this part may include a determination of the proportion of energy recovered over the FTP relative to the total available braking energy required over the FTP. This determination is required for pickup trucks accruing credits for implementation of hybrid technology under § 86.1870-12 , and requires the measurement of electrical current (in amps) flowing into the hybrid system battery for the duration of the test. Hybrid electric vehicles are tested for fuel economy and GHG emissions using the 4-bag FTP as required by § 600.114(c) . Alternative measurement and calculation methods may be used with prior EPA approval. (1) Calculate the theoretical maximum amount of energy that could be recovered by a hybrid electric vehicle over the FTP test cycle, where the test cycle time and velocity points are expressed at 10 Hz, and the velocity (miles/hour) is expressed to the nearest 0.01 miles/hour, as follows:(i) For each time point in the 10 Hz test cycle (i.e., at each 0.1 seconds): (A) Determine the road load power in kilowatts using the following equation: View Image
Where:
Proadload is the road load power in kilowatts, where road load is negative because it always represents a deceleration (i.e., resistive) force on the vehicle;
A, B, and C are the vehicle-specific dynamometer road load coefficients in lb-force, lb-force/mph, and lb-force/mph2, respectively;
Vmph = velocity in miles/hour, expressed to the nearest 0.01 miles/hour;
0.44704 converts speed from miles/hour to meters/second;
4.448 converts pound force to Newtons; and
1,000 converts power from Watts to kilowatts.
(B) Determine the applied deceleration power at each sampling point in time, t, in kilowatts, using the following equation. Positive values indicate acceleration and negative values indicate deceleration. View Image
Where:
ETW = the vehicle Equivalent Test Weight (lbs);
Vt = velocity in miles/hour, rounded to the nearest 0.01 miles/hour, at each sampling point;
Vt-1 = the velocity in miles/hour at the previous time point in the 10 Hz speed vs. time table, rounded to the nearest 0.01 miles/hour;
0.1 represents the time in seconds between each successive velocity data point;
0.44704 converts speed from miles/hour to meters/second;
2.205 converts weight from pounds to kilograms; and
1,000 converts power from Watts to kilowatts.
(C) Determine braking power in kilowatts using the following equation. Note that during braking events, Pbrake, Paccel, and Proadload will all be negative (i.e., resistive) forces on the vehicle. = Paccel-Proadload
Where:
Paccel = the value determined in paragraph (d)(1)(i)(B) of this section;
Proadload = the value determined in paragraph (d)(1)(i)(A) of this section; and
Pbrake = 0 if Paccel is greater than or equal to Proadload.
(ii) The total maximum braking energy (Ebrake) that could theoretically be recovered is equal to the absolute value of the sum of all the values of Pbrake determined in paragraph (d)(1)(i)(C) of this section, divided by 36000 (to convert 10 Hz data to hours) and rounded to the nearest 0.01 kilowatt-hours.(ii) The total maximum braking energy (Ebrake) that could theoretically be recovered is equal to the absolute value of the sum of all the values of Pbrake determined in paragraph (c)(1)(i)(C) of this section, divided by 36000 (to convert 10 Hz data to hours) and rounded to the nearest 0.01 kilowatt hours.(2) Calculate the actual amount of energy recovered (Erec) by a hybrid electric vehicle when tested on the FTP according to the provisions of this part, as follows: (i) Measure the electrical current in Amps to and from the hybrid electric vehicle battery during the FTP. Measurements should be made directly upstream of the battery at a 10 Hz sampling rate.(ii) At each sampling point where current is flowing into the battery, calculate the energy flowing into the battery, in Watt-hours, as follows: View Image
Where:
Et = the energy flowing into the battery, in Watt-hours, at time t in the test;
It = the electrical current, in Amps, at time t in the test; and
Vnominal = the nominal voltage of the hybrid battery system determined according to paragraph (d)(4) of this section.
(iii) The total energy recovered (Erec) is the absolute value of the sum of all values of Et that represent current flowing into the battery, divided by 1000 (to convert Watt-hours to kilowatt-hours).(3) The percent of braking energy recovered by a hybrid system relative to the total available energy is determined by the following equation, rounded to the nearest one percent: View Image
Where:
Erec = The actual total energy recovered, in kilowatt-hours, as determined in paragraph (d)(2) of this section; and
Ebrake = The theoretical maximum amount of energy, in kilowatt-hours, that could be recovered by a hybrid electric vehicle over the FTP test cycle, as determined in paragraph (d)(1) of this section.
(4)(i) Determination nominal voltage (Vnominal) using the following equation: View Image
Where:
VS is the battery voltage measured at the start of the FTP test, where the measurement is made after the key-on event but not later than 10 seconds after the key-on event; and
VF is the battery voltage measured at the conclusion of the FTP test, where the measurement is made before the key-off event but not earlier than 10 seconds prior to the key-off event.
(ii) If the absolute value of the measured current to and from the battery during the measurement of either VS or VF exceeds three percent of the maximum absolute value of the current measured over the FTP, then that VS or VF value is not valid. If no valid voltage measurement can be made using this method, the manufacturer must develop an alternative method of determining nominal voltage. The alternative must be developed using good engineering judgment and is subject to EPA approval. 76 FR 39548 , July 6, 2011, as amended at 76 FR 57380 , Sept. 15, 2011; 77 FR 63182 , Oct. 15, 2012; 79 FR 23747 , Apr. 28, 2014; 80 FR 9111 , Feb. 19, 2015; 81 FR 74001 , Oct. 25, 2016; 88 FR 4481 , Jan. 24, 2023 81 FR 74001 , 12/27/2016; 88 FR 4481 , 3/27/2023; 89 FR 28204 , 6/17/2024