The efficiency of the 48V motor generator shall be determined in accordance with ISO 8854:2012, with the exception of the elements specified in this section.

Evidence shall be provided to the type approval authority that the rotational frequency ranges of the efficient 48V motor generator are consistent with those set out in Table 1. The measurements shall be conducted at different operating points, as set out in Table 1. The efficient 48V motor generator current intensity shall be defined as half of the rated current for all operating points. For each rotational frequency, the voltage and the output current of the motor generator shall be kept constant, the voltage at 52V.

The efficiency at each operating point shall be calculated in accordance with Formula 1:

Formula 1

${\eta }_{{\mathrm{MG}}_i}=\frac{60\times U_i\times I_i}{\mathrm{2\pi }\times M_i\times n_i}\times 100$

All efficiency measurements are to be performed consecutively at least five (5) times. The average of the measurements at each operating point ($\stackrel{–}{{\eta }_{{\mathrm{MG}}_i}}$) shall be calculated.

The efficiency of the generation function (η_MG) shall be calculated in accordance with the following Formula 2:

Formula 2

${\eta }_{\mathrm{MG}}=\sum _{i=1}^4{h}_i\times \stackrel{–}{{\eta }_{{\mathrm{MG}}_i}}$

The efficiency of the 48V/12V DC/DC converter shall be determined under the following conditions:

• Output voltage of 14,3 V

• Output current of nominal power of the 48V/12V DC/DC converter divided by 14,3 V

The nominal power of the 48V/12V DC/DC converter shall be the continuous output power at the 12V side guaranteed by the manufacturer of the DC/DC converter at the conditions specified in the ISO 8854:2012.

The efficiency of the 48V/12V DC/DC converter shall be measured at least five (5) times consecutively. The average of all the measurements ($\overline{{\eta }_{\mathrm{DC}∕\mathrm{DC}}}$) shall be calculated and used for the calculations laid down in paragraph 3.3.

The total efficiency of the 48 V motor generator plus the 48V/12V DC/DC converter shall be calculated using Formula 3:

Formula 3

${\eta }_{\mathrm{TOT}}={\eta }_{\mathrm{MG}}\times \overline{{\eta }_{\mathrm{DC}∕\mathrm{DC}}}$

The 48 V motor generator plus the 48V/12V DC/DC converter generation function lead to saved mechanical power under real-world conditions (ΔP_mRW) and type approval NEDC conditions (ΔP_mTA) as set out in Formula 4.

Formula 4

ΔP_m = ΔP_mRW – ΔP_mTA

Where the saved mechanical power under real-world conditions (ΔP_mRW) shall be calculated in accordance with Formula 5 and the saved mechanical power under type-approval NEDC conditions (ΔP_mTA) in accordance with Formula 6:

• Formula 5

  ${\mathrm{\Delta P}}_{\mathrm{mRW}}=\frac{P_{\mathrm{RW}}}{{\eta }_B}-\frac{P_{\mathrm{RW}}}{{\eta }_{\mathrm{TOT}}}$

• Formula 6

  ${\mathrm{\Delta P}}_{\mathrm{mTA}}=\frac{P_{\mathrm{TA}}}{{\eta }_B}-\frac{P_{\mathrm{TA}}}{{\eta }_{\mathrm{TOT}}}$

where

• P_RW

  Power requirement under ‘real-world’ conditions [W], which is estimated at 750W

• P_TA

  Power requirement under NEDC type-approval conditions [W], which is estimated at 350W

• η_B

  Efficiency of the baseline alternator [%], which is 67 %

The CO₂ savings of the 48 V motor generator plus the 48V/12V DC/DC converter shall be calculated in accordance with Formula 7:

Formula 7

$C_{{\mathrm{CO}}_2}={\mathrm{\Delta P}}_m\times \frac{V_{\mathrm{Pe}}\times \mathrm{CF}}{v}$

where

• v

  Mean driving speed of the NEDC [km/h], which is 33,58 km/h

• V_Pe

  Consumption of effective power specified in Table 2:

  Table 2Consumption of effective power

  Type of engine	Consumption of effective power (VPe)[l/kWh]
  Petrol	0,264
  Petrol Turbo	0,280
  Diesel	0,220

• CF

  Conversion factor (l/100 km) - (g CO₂/km) [gCO₂/l] as defined in Table 3

  Table 3Fuel conversion factor

  Type of fuel	Conversion factor (l/100 km) - (g CO2/km) (CF)[gCO2/l]
  Petrol	2 330
  Diesel	2 640

The statistical margin of the results of the testing methodology caused by the measurements shall be quantified. For each operating point the standard deviation shall be calculated in accordance with Formula 8:

Formula 8

$s_{\stackrel{–}{{\eta }_{{\mathrm{MG}}_i}}}=\frac{s_{{\eta }_{{\mathrm{MG}}_i}}}{\sqrt{m}}=\sqrt{\frac{{\sum }_m^{j=1}{\left({\eta }_{{\mathrm{MG}}_{i_j}}-\stackrel{–}{{\eta }_{{\mathrm{MG}}_i}}\right)}^2}{m\left(m-1\right)}}$

The standard deviation of the efficiency value of the efficient 48V motor generator ($s_{{\eta }_{\mathrm{MG}}}$) shall be calculated in accordance with Formula 9:

Formula 9

$s_{{\eta }_{\mathrm{MG}}}=\sqrt{\sum _{i=1}^4{\left(h_i\times s\overline{\eta \mathrm{MG}i}\right)}^2}$

The standard deviation of the efficiency value of the 48V/12V DC/DC converter ($s\overline{\eta \mathrm{DC}∕\mathrm{DC}}$) shall be calculated in accordance with Formula 10:

Formula 10

$s\overline{\eta \mathrm{DC}∕\mathrm{DC}}=\sqrt{\frac{{\sum }_1^{j=1}{\left({\eta }_{\mathrm{DC}∕{\mathrm{DC}}_{i_j}}-\stackrel{–}{{\eta }_{\mathrm{DC}∕{\mathrm{DC}}_i}}\right)}^2}{l\left(l-1\right)}}$

The standard deviation of the motor generator efficiency ($s_{{\eta }_{\mathrm{MG}}}$) and of the 48V/12V DC/DC converter ($s_{\overline{{\eta }_{\mathrm{DC}∕\mathrm{DC}}}}$) lead to an uncertainty in the CO₂ savings ($s_{C_{{\mathrm{CO}}_2}}$). That uncertainty is calculated in accordance with Formula 11:

Formula 11

$s_{C_{{\mathrm{CO}}_2}}=\frac{\left(P_{\mathrm{RW}}-P_{\mathrm{TA}}\right)}{{\eta }_{\mathrm{TOT}}}\times \frac{V_{\mathrm{Pe}}\times \mathrm{CF}}{v}\times \sqrt{{\left(\frac{s_{{\eta }_{\mathrm{MG}}}}{{\eta }_{\mathrm{MG}}}\right)}^2+{\left(\frac{s\overline{\eta \mathrm{DC}∕\mathrm{DC}}}{\overline{{\eta }_{\mathrm{DC}∕\mathrm{DC}}}}\right)}^2}$

The efficiency of the 48V motor generator plus the 48V/12V DC/DC converter shall be determined in accordance with ISO 8854:2012, with the exception of the elements specified in this section.

Evidence shall be provided to the type approval authority that the speed ranges of the efficient 48V motor generator are consistent with those set out in Table 1.

The measurements shall be conducted at different operating points, as set out in Table 1. The efficient 48V motor generator plus the 48V/12V DC/DC converter current intensity shall be defined as half of the rated current of the 48V/12V DC/DC converter for all operating points.

The rated current of the 48V/12V DC/DC converter is defined as the output nominal power of the 48V/12V DC/DC converter divided by 14,3 V. The nominal power of the 48V/12V DC/DC converter shall be the continuous output power at the 12V side guaranteed by the manufacturer of the DC/DC converter at the conditions specified in the ISO 8854:2012.

For each speed the voltage and the output current of the motor generator shall be kept constant, the voltage at 52 V.

The efficiency at each operating point shall be calculated in accordance with Formula 12:

Formula 12

${\eta }_{{\mathrm{TOT}}_i}=\frac{60\times U_i\times I_i}{\mathrm{2\pi }\times M_i\times n_i}\times 100$

All efficiency measurements are to be performed consecutively at least five (5) times. The average of the measurements at each operating point ($\stackrel{–}{{\eta }_{{\mathrm{TOT}}_i}}$) shall be calculated.

The efficiency of the generation function (η_TOT) shall be calculated in accordance with Formula 13:

Formula 13

${\eta }_{\mathrm{TOT}}=\sum _{i=1}^4{h}_i\times \stackrel{–}{{\eta }_{{\mathrm{TOT}}_i}}$

The measurement set up has to allow the measurement of the 48V motor generation efficiency alone.

In order to use the procedure specified in 4.1 for the determination of η_TOT, it has to be demonstrated that the efficiency of the 48V motor generator alone obtained with the conditions specified in 4.1 is lower than the efficiency obtained with the conditions specified in 3.1.

The 48 V motor generator plus the 48V/12V DC/DC converter generation function lead to saved mechanical power under real-world conditions (ΔP_mRW) and type approval conditions (ΔP_mTA) as set out in Formula 14.

Formula 14

ΔP_m = ΔP_mRW – ΔP_mTA

Where the saved mechanical power under real-world conditions (ΔP_mRW) shall be calculated in accordance with Formula 15 and the saved mechanical power under type-approval conditions (ΔP_mTA) in accordance with Formula 16:

• Formula 15

  ${\mathrm{\Delta P}}_{\mathrm{mRW}}=\frac{P_{\mathrm{RW}}}{{\eta }_B}-\frac{P_{\mathrm{RW}}}{{\eta }_{\mathrm{TOT}}}$

• Formula 16

  ${\mathrm{\Delta P}}_{\mathrm{mTA}}=\frac{P_{\mathrm{TA}}}{{\eta }_B}-\frac{P_{\mathrm{TA}}}{{\eta }_{\mathrm{TOT}}}$

where

• P_RW

  Power requirement under ‘real-world’ conditions [W], which is estimated at 750W

• P_TA

  Power requirement under type-approval NEDC conditions [W], which is estimated at 350W

• η_B

  Efficiency of the baseline alternator [%], which is 67 %

The CO₂ savings of the 48 V motor generator plus the 48V/12V DC/DC converter shall be calculated in accordance with Formula 17:

Formula 17

$C_{{\mathrm{CO}}_2}={\mathrm{\Delta P}}_m\times \frac{V_{\mathrm{Pe}}\times \mathrm{CF}}{v}$

where

• v

  Mean driving speed of the NEDC [km/h], which is 33,58 km/h

• V_Pe

  Consumption of effective power specified in Table 2

• CF

  Conversion factor (l/100 km) - (g CO₂/km) [gCO₂/l] as defined in Table 3

The statistical margin of the results of the testing methodology caused by the measurements shall be quantified. For each operating point the standard deviation shall be calculated in accordance with Formula 18:

Formula 18

$s_{\stackrel{–}{{\eta }_{{\mathrm{TOT}}_i}}}=\frac{s_{{\eta }_{{\mathrm{TOT}}_i}}}{\sqrt{m}}=\sqrt{\frac{{\sum }_m^{j=1}{\left({\eta }_{{\mathrm{TOT}}_{i_j}}-\stackrel{–}{{\eta }_{{\mathrm{TOT}}_i}}\right)}^2}{m\left(m-1\right)}}$

The standard deviation of the efficiency value of the efficient 48V motor generator plus the 48V/12V DC/DC converter ($s_{{\eta }_{\mathrm{TOT}}}$) shall be calculated in accordance with Formula 19:

Formula 19

$s_{{\eta }_{\mathrm{TOT}}}=\sqrt{\sum _{i=1}^4{\left(h_i\times s\overline{\eta \mathrm{TOT}i}\right)}^2}$

The standard deviation of the motor generator and of the 48V/12V DC/DC converter efficiency leads to an uncertainty in the CO₂ savings ($s_{C_{{\mathrm{CO}}_2}}$). That uncertainty is calculated in accordance with Formula 20:

Formula 20

$s_{C_{{\mathrm{CO}}_2}}=\frac{\left(P_{\mathrm{RW}}-P_{\mathrm{TA}}\right)}{{{\eta }_{\mathrm{TOT}}}^2}\times \frac{V_{\mathrm{Pe}}\times \mathrm{CF}}{v}\times s_{{\eta }_{\mathrm{TOT}}}$