Plug-In Forum

With an electric car plug standard about to be finalized, and charging stations beginning to pop up in the U.S. and Europe, an important question to ask is: How long will it take to fill up a car battery? And like most technical matters, the answer is, “It depends.”

Automobile batteries, whether they are nickel-metal hydride or lithium-ion, can be made up of many cells, with larger cell quantities capable of a larger storage capacity. The tradeoff, however, is that cars with more capacity are more expensive, heavier, produce more heat and take longer to charge. Battery life is also influenced by how “deeply” the battery charges and discharges. For example, the Toyota Prius only allows its battery to be charged to 80% of full capacity, as going beyond this point can lead to overheating (thermal runaway) and excessive gassing, resulting in a decline in battery life. All this means that the type of car you own will play a factor.

The other major factor in charge times is the type of charging system being used. The standard wall socket in most U.S. garages output 120 Volts at 20 Amps of current. With this amount of power, it could take a whole night (8+ hours) to get the full electrical storage into a battery. Typical European outlets produce 230 Volts at around 16 Amps, perhaps shaving a couple hours off charging times.

For car owners wanting to drive far distances without the impossible hassle of waiting 8 hours between charges, there are a couple options available. In the U.S., plug-in charging stations will provide thick power cables that make it possible to deliver the 240 Volts at 70 Amps that the plug standard is designed to handle – this would make it possible to fully charge a vehicle in an hour or two. In Europe, the plug specifications provide for 400 Volts at 63 Amps. Theoretically, this can allow a waiting time measured in only minutes! However, with that sort of power, there is a risk of battery damage.

Car owners also have the option of using the high powered connections in their homes that are reserved for equipment such as air conditioners. They may also buy extra equipment, at a steep price. Unfortunately, residents who live in apartment buildings will not have access to many of these options.

For individuals who only drive short distances each day, simply charging their car overnight is practical and simple. Other prospective buyers will have to take into account the charging options available to them as well as the vehicle itself.

And in the not-so-distant future, advancements in battery technology should be expected to change the equation.

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