How a Car Battery Charges from High-Voltage Stations Using a Capacitor

This patent describes a vehicle power system that uses a capacitor in series with a lower-voltage battery to allow charging from standard electric vehicle charging stations that supply a higher minimum voltage.

What it covers

The patent details a vehicle power supply system designed to charge from an electric vehicle (EV) charging station that provides a voltage at or above a certain minimum, like 50 volts (Claim 2). The system includes a battery with a rated voltage lower than this minimum, for example, 48 volts (Claim 5). To bridge this voltage gap, a capacitor is connected in series with the battery (Claim 1). The combined rated voltage of the battery and capacitor together is higher than the charging station's minimum voltage. For instance, a 48V battery combined with a 72V capacitor (Claim 4) creates a 120V series, allowing it to interface with a 50V or higher charging station. The system's circuitry then manages the power received from the charging station to charge both the battery and the capacitor (Claim 1). An example of usage would be a mild-hybrid vehicle with a 48V battery system being able to use a public EV fast charger designed for higher voltage full EVs.

What it doesn't cover

• —Does not cover vehicle power systems where the battery's rated voltage is already equal to or greater than the charging station's lower limit voltage (Claim 1).
• —Does not cover systems where the capacitor is not electrically connected in series with the battery during charging (Claim 1).
• —Does not cover systems where the combined rated voltage of the battery and capacitor is less than or equal to the charging station's lower limit voltage (Claim 1).
• —Does not cover systems that only use a battery or only a capacitor for energy storage, without the series combination (Claim 1).
• —Does not cover charging systems that do not receive power from an external EV charging station (Claim 1).

The clever bit

The clever bit is using a capacitor in series with a lower-voltage battery to effectively 'boost' the perceived voltage for the charging station, making the combined unit compatible with higher-voltage charging infrastructure without requiring a complex, high-power DC-DC converter for the entire charging path.

Why it matters

This patent addresses a challenge for vehicles that use lower voltage battery systems, such as 48V mild-hybrids, which typically cannot directly use public EV charging infrastructure designed for higher voltage full electric vehicles. By enabling these vehicles to interface with standard EV charging stations, it could expand their charging options and convenience. This could be particularly relevant for Mazda, the assignee, as they have explored mild-hybrid technologies.

Real-world examples

• 1.Mild-hybrid vehicles with 48V electrical systems
• 2.Vehicles designed to charge from public EV charging stations with non-standard battery voltages
• 3.Future Mazda mild-hybrid or plug-in hybrid models