# How Electric Cars Adjust Charging Speed to Available Power

> This patent describes how an electric vehicle's onboard charger intelligently adjusts its charging speed based on the real-time electrical power available from the wall outlet or charging station, preventing overloads and optimizing charge time.

- **Patent:** US 20120091953
- **Original title:** Ac current control of mobile battery chargers
- **Owner:** Tesla Motor
- **Status:** Active
- **Times cited:** 11
- **Field:** automotive, consumer_electronics, energy, software

## What it does

The patent describes a system and method for an electric vehicle to manage its battery charging from an AC power source. It works by first figuring out the maximum amount of DC current the vehicle can safely draw, based on how much AC current or power is actually available at that moment (Claim 1a, 5a). Then, the onboard charging system provides an actual DC charging current to the battery, making sure it doesn't go over that calculated maximum (Claim 1b, 5b). For example, if you plug your Tesla into a household outlet, the car's system checks how much power that outlet can safely provide and then charges the battery as fast as possible without tripping the circuit breaker. More complex versions use control loops to fine-tune this process, comparing target voltages and currents to actual readings (Claim 2, 4).

## What it does NOT cover

- Does not cover charging systems that do not adapt to real-time available AC current or power.
- Does not cover off-board charging systems where the charger is external to the vehicle.
- Does not cover charging methods that only establish a fixed maximum DC current without responsiveness to real-time AC source conditions.
- Does not cover systems that lack a controller to adjust actual DC charging current based on input AC current (Claim 3).
- Does not cover charging of non-electric vehicle energy storage systems.

## The clever bit

The novelty lies in the system's ability to establish a real-time maximum DC charging current based on the actual available AC power, rather than just a pre-set limit. This dynamic adjustment optimizes charging speed while preventing electrical overloads.

## Real-world examples

1. Tesla Model S onboard charger
2. Tesla Model 3 onboard charger
3. Most modern electric vehicle onboard charging systems
4. Portable EV charging cables with adjustable current settings

## Why it matters

This patent is significant because it addresses a core challenge in electric vehicle charging: safely and efficiently using varied AC power sources. By dynamically adjusting the charging current, it allows EVs to charge at the fastest possible rate without overloading electrical circuits, which is crucial for user convenience and grid stability. This capability is fundamental to modern EV charging, enabling vehicles to adapt to different charging environments, from standard home outlets to dedicated charging stations.

## Frequently asked questions

### What does How Electric Cars Adjust Charging Speed to Available Power cover?

This patent describes how an electric vehicle's onboard charger intelligently adjusts its charging speed based on the real-time electrical power available from the wall outlet or charging station, preventing overloads and optimizing charge time.

### Who owns patent US 20120091953?

This patent is owned by Tesla Motor.

### When does this patent expire?

This patent is expected to expire on October 13, 2030, when the invention enters the public domain.

### What is patent US 20120091953 cited by?

This patent has been cited by 11 later patents that build on its ideas.

### What problem does this patent solve?

This patent is significant because it addresses a core challenge in electric vehicle charging: safely and efficiently using varied AC power sources. By dynamically adjusting the charging current, it allows EVs to charge at the fastest possible rate without overloading electrical circuits, which is crucial for user convenience and grid stability. This capability is fundamental to modern EV charging, enabling vehicles to adapt to different charging environments, from standard home outlets to dedicated charging stations.

### What does this patent NOT cover?

Does not cover charging systems that do not adapt to real-time available AC current or power.

**Full plain-English explainer:** https://patentbrief.org/patent/us/20120091953/ac-current-control-of-mobile-battery-chargers

**Original patent:** https://patents.google.com/patent/US20120091953

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_Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._