Tech’splaining: Electricity – Amps, Watts, Volts, Oh My!

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The flow of electricity can be compared to the flow of water. A wiring system and a plumbing system have many similarities. If you want to understand how electric cars work, and how different aspects of electricity impact performance, visualize the flow — and consider these few basic terms:

Voltage: In the analogy of water flow, the voltage would be the same as pressure in the pipe. It is how hard the electrons are being pushed through the pipe(wire).

Amperage: This is your current, similar to the amount of water flowing in a pipe or the size of the pipe.

Watts: When you combine pressure and the amount of water, you figure out how much power the system has. Similar to horsepower, in that it is a force delivered over a time, a Watt is a unit of power, like horsepower in an ICE car.

Kilowatt-Hour(kWh): This is a unit of energy, meaning it is power over a period of time. In this case, it is 1,000 Watts delivered over one hour. If an electric vehicle uses 1 kWh of energy, that’s the same as an ICE car using 1.34 horsepower for 1 hour; or, to extend the plumbing analogy, picture gallons per flush.
A system of pipes makes an easy to understand analogy for electrical circuits
A system of pipes makes an easy to understand analogy for electrical circuits. Volts are pressure, Amps are the size of the pipes. (Image: Getty Images)

What do voltage, Watts and kWhs all have to do with how an electric vehicle or even a hybrid electric vehicle will perform?

First, voltage; we are seeing voltage increasing in EVs as technology advances. New materials in controllers and semiconductors are allowing designers to build systems running as high as 800 volts allowing for faster charging times, almost twice as fast as at 400 volts.

Chargers are generally rated in Watts. A Level 1 charger is 120-volts at 8 to 12 amps, so we are looking at 0.96 kW up to 1.4 kW common for in-home charging from a regular wall socket. Install a Level 2 charger at home and it operates on 240-volts and can reach up to 80 amps, delivering 19.2 kW. Once we get up to Level 3, we switch to Direct Current of DC technology, which allows up to 600 volts and 400 amps. Eventually, Porsche plans to build a network of 350 kW Turbo Chargers in the United States.

The Production Porsche Taycan Will Operate At 800 Volts
When the production version of Porsches all-electric Taycan hits showrooms, it will reportedly have the ability to charge using an 800 volt charger, cutting charging times to a fraction of other EVs. (Image: Porsche AG)

Electric car batteries are rated in Kilowatt-Hours(kWh). If we look at the units, it’s power and time. As a driver, you can choose if you want to use more power in a short amount of time, or use a little bit of power over a long period of time. Drive fast for a few minutes or drive slow for hours, just like gas in a tank. The largest battery capacity in a vehicle at the moment is a Tesla Model S with a 100 kWh battery giving you 370 miles of driving range. A mild-hybrid like the Mercedes s400 uses a tiny 0.8 kWh battery used mostly for getting the vehicle rolling from a stop and reclaiming lost energy during braking.

The further we get into the electrified future, the greater battery capacity we will see in cars and the faster charging speeds we’ll see at specially built stations. At home chargers will likely remain mostly limited to the amount of electricity that can flow through your home. With new battery chemistry and higher voltage electronics inside EVs, it isn’t crazy to think that we will see vehicles with 500 miles or more of range that can add a couple of hundred miles of range in the time it currently takes to fill up your gas tank.


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