VS - Electrical Systems From Stop-Start to Hybridization

21

Impacts on the electrical system

Cranking pulse parameters

Parameter

Normal cranking

Severe cranking

U

U U U U U

11,0 V 4,5 V 4,5 V 6,5 V ≤ 1 ms 0 ms 0 ms 19 ms 50 ms 2 V

11,0 V

B

3,2 V +0,2 V

T

Battery cranking phase

5,0 V 6,0 V

S

U

A

B

2 V

R

1/f

t t t t t t t f

≤ 1 ms 19 ms ≤ 1 ms 329 ms 50 ms

F

U

4

R

U U

A

5

S

6

U

7

T

10 s

10 s

8

100 ms

100 ms

R

t

t

t

t

t

t

t

t

2 Hz

2 Hz

F

4

5

6

7

8

R

R

0,01 Ω

0,01 Ω

I

Among all characteristics required by car-makers for starter circuits, the minimal voltage level at battery is particularly critical: as an absolute value itself and versus time as well. This requirement is illustrated in the so called pulse N°4 as a simplified description of the battery voltage during the cranking phase. The pulse N°4 defines voltage and time boundaries, values depend on car makers, vehicles generations and their respective electrical architectures.

During the cranking phase a huge amount of electrical energy is required to put in motion the engine crankshaft and engage the engine combustion cycle, this sudden power demand creates an important voltage drop on the board-net, it is a major constraint for all Electronic Control Units (ECU) that are embedded in vehicles. The cranking pulse At this early stage, the unique energy source is the battery, it has therefore to be charged enough to supply energy to the starter system and to all electronic equipments that require to be either minimally energized, waken-up or totally active during cranking.

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