Electric Car Charging: The Basics

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Electric Car Charging: The Basics

You finally got that plug-in electric car.  Now you’ve got to plug it in.

Getting the right size charging station — or determining whether you’ll need one at all — isn’t as daunting as it may seem. Just read along:

The basics

Charging speed

Can I overdo it?

What is a charging station?

Do I really need a charging station?

Where do I get a charger?

What’s it cost?

How do I get it installed?

The basics

The first thing to know about plug-in vehicle, or PEV, charging is that there are three levels of power delivery.

  • Level 1 charging, the slowest method, uses standard household current, 120 volts, and doesn’t require dedicated lines or special high-power circuit breakers. Level 1 charging typically provides power at a rate sufficient to add 3 to 5 miles of range per hour to a depleted PEV battery pack.
  • Level 2 charging, the standard for most home and public charging stations, requires a dedicated 240-volt circuit and can deliver power at various rates, depending on the size — or amperage — of the circuit. Most professional installers recommend 30- or 40-amp systems, sufficient to handle overnight charging for most PEVs as well as between-trips “top-up” charging so you don’t run out of range while running errands on weekends.
  • Level 3 charging, also called rapid or quick charging, draws 480 volts of power and requires an equipment housing that’s about the size of a gas station pump, making it impractical for home use. Level 3 systems are designed to take a battery from near-depletion to 80% of capacity in about 30 minutes and are intended to facilitate longer trips than a single home charge will permit.

Level 1 and Level 2 charging deliver power to the car through a special plug-in connector nozzle that is standard throughout the U.S. for both levels of charging.

There are three different Level 3 systems in use in the U.S. One, for a few Asian models, notably the Nissan Leaf and Kia Soul EV, is called the CHAdeMO system; one used exclusively by Tesla is the Tesla Supercharger system; and the third, used by all European and U.S. models and some Asian models, is the SAE Combo system. Each has its own dedicated connector nozzle.

Tesla’s widespread network of Superchargers is the only one so far to enable cross-country travel (Tesla also offers a CHAdeMO adapter). Other Level 3 stations are typically found at plug-in electric car dealerships in urban areas and along heavily traveled regional transportation corridors; most offer both CHAdeMO and SAE connections. A site called PlugShare.com will map nearby charging stations for you.

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Charging speed

How quickly you can charge your plug-in car depends on the amperage of the charging circuit and the capacity of the car’s charger, which is rated in the number of kilowatts it can take in per hour.

Most plug-in hybrids have 3.3-kW chargers. Some all-electric cars still have 3.3-kW chargers, but most now offer at least 6.6-kW charging and some go higher. Teslas, for instance, all start at 10 kW, and there’s an option to double that to 20 kW per hour.

To determine how fast any given charging station will be, multiply the rated amperage by the voltage and divide by 1,000 (the number of watts in a kilowatt). A Level 2 charging station rated at 30 amps will deliver 7.2 kW per hour: 240 x 30/1000. It will service cars with on-board chargers rated at 7.2 kW or less. It also would work for 10-kW charging, but it wouldn’t charge the car at its rated speed. For that you’d need to buy at least a 40-amp system.

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Can I overdo it?

All charging degrades batteries, and Level 3 charging is harder on them than Level 1 or Level 2 charging. Repeated use of rapid charging can shorten the useful life of a PEV’s batteries.

The big culprit is heat, and as a charging battery approaches full capacity, the heat generated by the process increases. The process of draining and recharging also impacts the battery’s internal chemistry and its ability to store and hold a charge. Many PEV specialists recommend keeping batteries charged at no more than 80% of capacity when possible. (As a safety measure, most PEV battery packs are designed to still have some unused capacity when the charging status gauge reads “full.”)

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What is a charging station?

Everyone calls them chargers, but the wall boxes and stanchions we plug our electric vehicles into are really just communication and safety devices. The real chargers, except for the high-power Level 3 chargers, are actually part of the vehicle.

The proper name for a home charger is electric vehicle service equipment, or EVSE.  But if you go shopping for a “home charging station,” everyone will know what you want.

The EVSE communicates with the car’s charging system to regulate power and keep the battery pack from overheating. It also can shut down to avoid an electrical fire in case of a short, and it anchors the charging cord to the wall and provides a place to store the coiled cord.

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Do I really need a charging station?

How valuable is your time?

All PEVs come with a Level 1 cord set that you can use to charge your car from any standard wall socket. If you can get enough juice into the battery pack with a Level 1 cord to enable you to use the car as much as you need, then you won’t have to buy a Level 2 home charging station.

But on average, that Level 1 cord set is going to deliver power at a fairly slow rate — generally enough to add 3 to 5 miles of range to your battery pack each hour. Many plug-in hybrids can be charged overnight at Level 1. A model with a battery capable of providing 20 miles of all-electric range would take four to seven hours to recharge that way.

But a battery electric vehicle that provides 90 miles of range between charges would take 18 hours or more to recharge on a Level 1 system — if you completely depleted the battery. Keep in mind that the average American drives only about 29 miles a day, according to AAA, and consider your own driving habits and needs. Many drivers of battery electric vehicles get by with overnight charging on Level 1.

Level 2 charging, that standard for home systems and most public charging stations, provides power at a much faster rate — 10 to 25 miles of range per hour.

It’s most convenient to charge your car when it’s parked at home and you’re not planning to use it for a while. But some PEV owners find that they can get away with charging while at work, if their employer offers workplace charging or a public charging station is nearby. And some have found it feasible to use publicly available chargers at retail, entertainment and government centers near their home or workplace, most of which charge a set fee per hour of charging.

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Where do I get a charger?

Most dealerships that sell plug-in vehicles also sell home charging stations; carmakers often have a preferred EVSE supplier.

But you don’t have to buy a BMW-branded home station just because you’re buying or leasing a BMW i3. Most charging stations can be used with most plug-in vehicles. Tesla is the outlier with its own proprietary charging system. Tesla owners can purchase adapters that enable them to use non-Tesla EVSEs, but most are slower than the Tesla system.

You can save money by shopping online at Amazon and eBay or from big-box home improvement stores such as Lowe’s and Home Depot. You can also buy directly from many charging-equipment makers via their websites.

The major home EVSE makers include AeroVironmentBlinkBoschClipperCreekDelta Energy SystemsEatonEvatran GroupEVoChargeGeneral Electric, Leviton and Siemens.

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What’s it cost?

Home EVSEs run from around $300 to more than $1,000; you’ll also have the cost of installation (more on that below).

The price of the EVSE depends on the power levels, cord lengths and extras such as Wi-Fi capability, timers for delayed and time-of-day charging — most PEVs have on-board timers that handle that — and even automated record-keeping to help you track power usage.

You can get charging cord sets with Level 2 capacity that eliminate the wall-mounted station. But they typically provide slower charging rates and still require a dedicated 240-volt circuit.

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How do I get it installed?

Most qualified electricians can install an EVSE system in your garage, carport or other residential parking spot. Some rental property landlords and apartment complex operators will permit tenants to install EVSEs, although installing in a remote parking area or structure can be quite costly.

In most jurisdictions, you’ll need a building permit, and it’s always wise to check with your utility company to see if it offers special rates for plug-in vehicle charging. Many do.

Installation costs vary widely depending on labor rates in your area, the amount of work involved in installing the required circuitry and the distance, or “run,” between the home electric service box and the charging station. A normal installation is likely to cost between $250 and $750, and systems that require long runs, additional breaker panels or other special equipment and labor can easily cost double that.

Some EVSEs require a hard-wired installation, while others can be plugged into a dedicated 240-volt wall socket.

Often, your local electric utility will be able to provide a list of qualified installers.

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John O’Dell is a longtime automotive writer who has covered alternative-fuel cars for the Los Angeles Times and Edmunds.com. He now runs the website The Green Car Guy. Email: thegreencarguy@gmail.com.