Volts, Amps, Watts- What do they mean?

By August 22, 2012July 7th, 2018How do we do it?, Jim's Blog

We are all familiar with miles per gallon for gasoline vehicles, but there is a new vocabulary used with electric vehicles. This vocabulary is often confusing, because we are not familiar with it.  It is necessary to understand this new  vocabulary to be able to compare electric bikes and make a good buying decision. The vocabulary of electric bikes is not hard, just new.  In this issue we start with  a very short and simple lesson on the basic terms used to determine power and range.

The terms Volts, Amps, Watts, and Watt-hrs are often used to describe the performance of electric bikes, but what do these terms mean and how are they related? Electricity flow is similar to water flow in a hose.

The potential of a battery to do work is measured in  Volts. Volts are similar to the pressure of water  in a hose.

Volts by themselves can do no work,   unless accompanied by flow, which is current, measured in Amps.  Current is similar to  the flow of water in the hose.

To get anything done, we need Voltage with Current flow. (All the voltage in the world will do no work if current does not flow. Imagine a hose faucet that is closed, nothing happens until the faucet is opened and water flows.).   Power is measured in Watts.  The power of motors is measured in Watts.

Power (watts)= Voltage (volts) X Current (Amps)

When Watts are used for a period of time, this is Energy, which is measured in Watt-hours. Watt-hrs is how we are charged for our electricity.

Energy(watt-hrs)= Power(Watts) X Time(hrs)

The capacity of a battery is measured in Watt-hrs,. Battery capacity is also  referred to in amp-hrs, but this is not a full description, since amp-hrs do not include the voltage of the battery to give a true Energy capacity.

Next issue we will discuss battery capacity and how it is measured.

Jim Turner

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