Home electric vehicle charger basics

Picture by Devon Jarvis
Date:27 February 2014 Tags:,

Considering an electric vehicle? The appropriate charger will make living with it easier. By Michael Austin

Degree of Difficulty: 9/10 | Unless you have ample experience with home electrical work, this is probably a task best left to a professional.

Imagine never going to the filling station again. Such convenience is one of the key advantages of an electric vehicle, although it comes with two drawbacks: short range (sometimes less than 100 kilometres) and long charging times. Unless you can afford a Tesla Model S (R700 000 in the USA), which goes nearly 500 km on a charge, there’s not much you can do about an electric vehicle’s limited range.

Charging time is a problem, too. Where many of the world’s EVs are found, in the US, home charging can take up to 18 hours on that country’s 110 AC mains, which provides an input power of 1,92 kW. With a Level 2 (240-volt) charger that time shortens markedly to as little as 3 hours, with considerably greater power available. For plug-in hybrids, this means that instead of tapping into the fuel tank, you can restore the car’s electric range after you get home from work and before you head out for a night on the town.

Of course, this is probably a job for a professional electrician. The good news for US consumers is that many electric utilities offer incentives that cover the cost of a charger and its installation. In South Africa, it’s early days yet, with just the Nissan Leaf on the market; Nissan has for now bundled a home charger set-up with the car. With the likelihood that electric cars will gradually grow in popularity, here are the key things you need to know to get your house EV-ready.

Pick your charger
EVs and plug-ins tend to use the SAE standard J1772 plug. Although they work more or less the same way, not all chargers are created equal.

Cost: The two biggest factors are current and cord length: if you want more, expect to pay more. Installation type: This unit is meant to be a permanent installation, mounted to the wall on a bracket. But some are classified (confusingly) as “permanently installed, removable” and use a standard plug so you can take the charger with you if you move.

Current: Level 2 chargers come in 16- or 30-amp flavours. A 16-amp charger works fine for plug-ins such as the Chevrolet Volt, which doesn’t draw more current than that, and can often be installed with your existing wiring. But 30 amps should be the default, as it provides maximum charging speed and futureproofs your purchase if you buy a second electric vehicle.

Cord length: The location of the charger in your garage will depend on how far you’ll need to reach to access the car’s charge port. A Nissan Leaf, for instance, is about 4,4 metres long and charges from the nose. We recommend a spot close to the garage door, so you can charge your car even if you’re parked in the driveway. A 5- or 6-metre cord should be fine, but go longer if you can afford it. These units can’t be retrofitted if you’ve left yourself short.

Get Your House Ready
The biggest potential headache with an EV charger is whether you have proper electrical service. If your house can’t handle the extra load of a charger, you’re dealing with an even bigger project of getting a new service drop, which means cutting off power to the house and installing a new meter and breakerpanel.

You’ll also need to consider the age of your garage and its distance from the house. Old wiring going to the garage might need to be replaced, and longer distances can come with a nominal increase in the size and cost of the cable that runs to the charger. In most instances, though, an electrician will be able to properly wire your garage. If you’re experienced with home wiring, make sure you follow all the guidelines.

Ignoring them carries a very real risk of an electrical fire. The US National Electrical Code Article 625 covers the rules for EV-charger installation, such as where a charger can be mounted and what kind of wiring is required.

If you don’t have a garage, you can install a charger in your driveway. For outdoor mounting, you’ll want a unit with a NEMA (National Electrical Manufacturers Association) rating of 4X – the Bosch Power Xpress is one example – which is made to stand up to rain, cold and dust.

What’s so special about that plug?
The SAE J1772 charging plug is as inelegant as its name. And the five ports that connect to your car might seem complicated, but they’re actually pretty straightforward.

AC power, just like the power plug for your TV.
Proximity detection. This is simply a mechanical switch that makes sure you’re plugged in all the way.
Earth wire. Communications, used to relay data between the car and the charger about how much current is needed.