Range Confidence: Charge Fast, Drive Far, with your Electric Car

By David Herron

How do I charge away from home?

Gasoline cars can only be refueled away from home, and it's an easy task since gasoline stations exist nearly everywhere. Finding charging stations can be tricky. They're not as widely deployed as gasoline stations, and there's no convenient blaring signs standing 100 feet tall for everyone to see.

Finding charging away from home

Now that you have this book in your hands, you should know how to find charging away from home. Let's review:

  1. Step 2 – Know your local EV charging terrain: Suggests familiarizing yourself with charging station maps. This gives you a list of local charging stations to use away from home.
  2. Step 6 – Charging station network memberships and smart phone apps: Suggests that you join all the charging station networks in your local area.

Once you've taken these steps you're ready to charge your electric car away from home.

The charging process away from home

You will probably have used a home charging station. The physical process is similar to what you do at home.

Authenticate: Some charging station networks require you authenticate yourself in order to start a charging session. This lets the network control access, charge fees, send notifications via text message to your cell phone, etc. Authentication methods include:

  • Waving an RFID card over a reader
  • Reading a QR-Code with a cell phone app
  • Paying with credit card

Other charging networks do not require authentication. The charging station map applications usually tell you whether authentication is required, and if so which charging station network. Before you drive miles to a charging station, it's useful to know whether you're a member of the necessary charging network.

Plug in: If you're at a Level 2 station, this will be identical to what you do at home. However if you're at a fast charging station the charging plug will be different. Make sure to familiarize yourself with the plug.

Start the charging session: This may not be necessary, depending on the charging station design. In some cases you must press a button. For example some multi-cord stations require you to select the cord to use.

Inspect display or smart phone app: Most charging networks supply a smart phone app through which you can monitor the charging session, among other functions. In most cases you can monitor the session from any distance, thanks to modern data communications wizardry.

Portable charging stations and guerrilla charging

Sometimes when needing charging while away from home you'll be unable to find a proper Level 2 (or DC Fast Charging) station. You still need to charge, so what do you do?

At the core this problem is similar to driving a gasoline car past the "Last Gas for N Miles" signs, and run out of gasoline far from the nearest gasoline station. In both cases you don't have a convenient refueling station, but you still need refueling in order to reach a destination. With an electric car it's easier to get caught this way, because currently the charging infrastructure is inadequately distributed.

In our modern world, electricity exists pretty much everywhere. Even in the places where there's no gasoline stations it's possible to arrange for electricity. All that's necessary is to carry a portable charging station.

Every electric car is sold with one - the "line cord charger" that runs at about 1.2 kiloWatts. Unfortunately the charging rate is rather inconvenient, because a full recharge will take 20 hours or more. Fortunately there are higher power charging stations available, that can be carried along. Some are even capable of a 6 kiloWatt or more charging rate.

I've created a guide to portable charging stations, extension cords, and the various kinds of power outlets you'll find "in the wild". See Safely use Extension Cords when charging an electric car or electric motorcycle What follows is a simplified summary.

High power outlets: Electricity is pretty much anywhere, the trick is finding those that give enough power to charge at a decent rate. In the U.S. the "NEMA 14-50" outlet supplies up to 240 volts and allows 40 amps continuous current draw. That's enough for the 6+ kiloWatt charging stations. But not all 240 volt outlets provide 40 amps continuous power. The NEMA 6-20 outlet is rated for 20 amps peak, or 16 amps continuous power. That's only about 3 kiloWatts, insufficient for the 6 kiloWatt charging station.

Finding power outlets: You can just ask around and see what you find. Likely places are RV Parks, Laundromats, or any shop with welding equipment or other high power tools. Many homes have "dryer outlets" that run at higher power. The PlugShare app has, among the crowdsourced list of charging stations, places that make power outlets available to EV drivers. See Smart-phone apps for finding electric car charging station networks

Adapters: In the U.S. there is unfortunately a wide array of different 240 volt outlets and plugs. Your portable charging station may have come with a NEMA 6-50 plug, which won't plug into a NEMA 14-50 outlet even though both are 240 volt 50 amps peak. It means building (or buying) suitable adapters.

Power ratings: You must be sure the power outlet you're using is rated for the charging station's current draw. Most charging stations cannot adjust their power draw. You don't want to draw more than the plug you're using allows. Maybe all that'll happen is popping the circuit breaker. You'll have the inconvenience of having to reset the circuit breaker, but what's worse is you won't be able to charge because the charging station draws more power than the circuit allows. See Electric car charging within electrical code and power outlet limits

Your car may be able to adjust the power level it requests. If so, set the car to not draw more than the circuit allows.

The maximum continuous current is 80% the peak power rating. For example, a 20 amp rated outlet (like the NEMA 6-20) only supports 16 amps (20 amps * 80% is 16 amps) continuous.

Extension cords: All the automakers and charging station makers recommend against extension cords. A long cord creates a "voltage drop" that then causes bad results that can include heating. Not all extension cords are equal, and the skinny cheap cords will heat up more quickly than thick ones. To be clear, we're talking about thickness of the actual wire. Enough heat and you have the chance of a fire. Rather than explain all this to you, these manufacturers just say don't use an extension cord. See Safely use Extension Cords when charging an electric car or electric motorcycle

If you must use an extension cord make sure it's a thick one. At the minimum use cords with 10 gauge wiring. But even that is insufficient for a 6 kiloWatt charging station. At 240 volts, running 30-40 amps continuous requires at least 6 gauge wiring for a reasonably long cord. Such extension cords do exist, if only for welders.


Range Confidence is Copyright © 2016-17 by David Herron

How do I charge away from home?

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