# US 9,752,547 B2 · Electrical system for a vehicle with start/stop

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- Number: US 9,752,547 B2
- Document ID: US9752547B2
- Status: Granted
- Kind: B2
- Application number: 13/527,204
- Filed: 2012-06-19
- Published: 2012-12-27
- Granted: 2017-09-05
- Earliest claimed: 2011-06-22
- Assignees: Volvo Car Corporation
- Applicants: Oerjan Spjuth; Torbjoern Larsson; Daniel Midholm; Fredrik Ulmhage
- Inventors: Oerjan Spjuth; Torbjoern Larsson; Daniel Midholm; Fredrik Ulmhage
- Web page: https://patentgrep.com/patent/US9752547B2

## CPC

- F02N 11/0866: {comprising several power sources, e.g. battery and capacitor or two batteries}
- F02N 2011/0885: {Capacitors, e.g. for additional power supply}
- F02N 2011/0888: {DC/DC converters}
- F02N 2250/02: Battery voltage drop at start, e.g. drops causing ECU reset
- F02N: STARTING OF COMBUSTION ENGINES; STARTING AIDS FOR SUCH ENGINES, NOT OTHERWISE PROVIDED FOR

## Abstract

An electrical system for a vehicle having an internal combustion engine with start/stop capability includes a primary battery connectible to an engine starter motor; a secondary battery, an alternator, and an electrical load in parallel with one another and selectively connectible in parallel with the primary battery by a charge switch; in parallel with the secondary battery, a DC/DC converter in series with a third electrical energy source; and a bypass switch operable to selectively bypass the DC/DC converter. The bypass switch allows for selective bypassing the DC/DC converter and charging/discharging of the third electrical energy source during start/stop operation, to ensure a sufficient voltage level over the additional vehicle electrical loads when the internal combustion engine and consequently the alternator are not running.

## Claims

### Claim 1

A method for operating an electrical system of a vehicle having an internal combustion engine provided with a start/stop system enabling shutoff of the internal combustion engine while electrical systems of the vehicle are running, the electrical system further comprising a primary battery selectively connectible to a starter motor for the internal combustion engine via a starter solenoid, a secondary battery, an alternator, and additional vehicle electrical loads arranged in parallel with one another and selectively connectible in parallel with the primary battery via a charge switch, the method comprising:
arranging in parallel with the secondary battery a DC/DC converter in series with a third electrical energy source;
and providing a bypass switch for selectively bypassing the DC/DC converter.

### Claim 2 (depends on 1)

The method of claim 1, further comprising arranging as the third electrical energy source a super-capacitor.

### Claim 3 (depends on 1)

The method of claim 1, further comprising arranging as the third electrical energy source a lithium-ion battery.

### Claim 4 (depends on 1)

The method of claim 1, wherein when the engine is stopped during a start/stop event the electrical system is operated such that:
the charge switch is open;
the bypass switch is open; and
the DC/DC converter is boosting.

### Claim 5 (depends on 1)

The method of claim 1 wherein to achieve a cold-start of the engine the electrical system is operated such that:
the starter solenoid is closed to supply power to the starter motor;
the charge switch is open;
the bypass switch is open; and
the DC/DC converter is off.

### Claim 6

A method of operation of a motor vehicle, the vehicle having an internal combustion engine operable in a start/stop mode enabling shutoff of the internal combustion engine while electrical systems of the vehicle are running, and an electrical system including a primary battery selectively connectible to a starter motor for the internal combustion engine via a starter solenoid; a secondary battery, an alternator, and additional vehicle electrical loads arranged in parallel with one another and selectively connectible in parallel with the primary battery via a charge switch; and, in parallel with the secondary battery, a DC/DC converter and associated bypass switch in series with a third electrical energy source, the method of operation comprising:
when the engine is stopped during a start/stop event:
the charge switch is open, the bypass switch is open, and the DC/DC converter is boosting; and
during a warm-start of the engine after a start/stop event:
the starter solenoid is closed to supply power to the starter motor, the charge switch is open, the bypass switch is open, and the DC/DC converter is off.

### Claim 7 (depends on 6)

The method of claim 6 further comprising:
during a cold-start of the engine:
the starter solenoid is closed to supply power to the starter motor, the charge switch is open, the bypass switch is open, and the DC/DC converter is off.

### Claim 8 (depends on 6)

The method of claim 6 further comprising:
when the engine is running after either a warm-start or a cold-start:
the charge switch is closed, the bypass switch is closed, and the DC/DC converter is off.

### Claim 9 (depends on 6)

The method of claim 6 further comprising:
when the vehicle is in a state of long-term parking:
the charge switch is open, the bypass switch is open, and the DC/DC converter is off.