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Sunday, December 1, 2013

EV Charging at Home - What to Buy

A friend of a friend recently bought an EV and wanted to know what to buy for home charging. They asked me via email. Since I didn't know the person, nor their specific situation, I wrote some general guidelines to picking out a home charging station that might help you, a friend (or a friend of a friend).

First, a few brief things you need to know:

One, the charger is onboard your car. The charging station that you plug into your car is just a way to safely deliver power with a standard connector. That is why you will occasionally see charging stations referred to by their technical name of electric vehicle supply equipment (EVSE).

Two, charging stations are rated by how much power they can deliver. Similarly, the onboard charger has a power limit. These limits are rated in kilowatts (kW). How fast your car charges is based on whichever is lower, the car's onboard charger or the charging station, so you'll want a home charger that is well matched to your car or your needs.

How to pick a home charging station

There are a lot of options for home charging. The right choice for you will depend on:
  • What vehicle you have
  • How much recharge time matters to you
  • How much you are willing to spend
  • How much of a DIY person you are
Note: I live in the US, so this will be US focused.

If you just bought a Tesla Model S, congratulations, and they have service reps that can help you with this decision, so I'll assume you bought a Leaf, Volt, Spark, or one of the many other plug-in cars that are now on sale.

Option 1 - Trickle Charger

Most new plug-in cars come with a Level 1 supply unit a.k.a. a "trickle charger". For some people, these alone are adequate. They plug in to any standard home outlet. They charge your car slowly, but they are easy to use and don't cost you anything extra. At a mere 1.3kW, they generally only give you 4-5 miles of range per hour, so they work well for overnight charging but don't expect to be able to drive to near empty in the AM and have a full charge after lunch. For a plug-in hybrid such as the Volt, Plug-in Prius, or Ford C-MAX Energi this could be enough. For a 100% battery electric such as the Leaf or Ford Focus Electric, this is not my preference due to the slow charging rate.

Option 2 - Portable Level 2

Whereas the trickle charger plugs into a standard home outlet, a portable Level 2 supply plugs into a 240 Volt outlet such as a dryer plug. Portable chargers are nice since you can take them with you on the road. You can charge up at campsites and I have thrown a cord out of my brother-in-law's laundry room window when I needed to charge up.

There are two portable Level 2s that I am aware of:

1) Clipper Creek's "On the Road" series
This option is ~$550 and you'll need a 240V outlet in your garage. If you don't already have a 240V outlet, it is generally less than $400 to have an electrician install one or you can do it yourself if you are handy that way. At 4.8kW, this will give you a max of 18 miles of range per hour that you're plugged in.

2) EVSEUpgrade.com
Option 2 is to have your trickle charger upgraded at evseupgrade.com. Depending on the charger you have, the upgrade prices vary, they are generally $250 - $300. The nice thing about this option is that you can buy adapters so you can use it at various types of 240V outlets (RV, dryers, welders...) and 120V outlets.

Option 3 - Wall-Mounted, Hard-Wired Level 2

The third option is a wall mounted unit. If you want advanced features such as timers, Internet connectivity, or energy reports, then this is your category. These are typically installed in your garage, carport, or wherever your car is usually parked for the night. They have the advantage of always being in the same place. It is highly unlikely that you'll pull into your own garage to find out that it has been borrowed by your neighbor for a cross-state EV road trip.

You can find many options for these at Amazon.com or Home Depot online. Just search for "EVSE". The prices range from ~$500 to over $2000 plus installation. Once installed, these are the most convenient to use. The two most important features to consider are the cord length and the power rating. There are options at 3.8kW, 7.2kW, 7.7kW, 9.6kW. Each 1kW will give you about 4 miles of range per hour. Remember, a power rating above the level of the car's onboard charger does not do anything for you. Assuming the car has a 6.6kW charger, a 6.6+kW unit will give you about 25 miles of range per hour.

Option 4 - DIY

The final option I'll offer is the home-brew maker option. There are Arduino-based and Kickstarter some-assembly-required charging stations. If you are the hobbyist type, you might consider one of these and I'll leave you on your own to investigate them.

Your Choice 

For me, I have a combination. At home I have a wall mounted Level 2. This makes it easy to charge up each night. Additionally, I have an EVSEUpgrade.com unit with 6 or 7 adaptors. These adaptors allow me to me to use nearly any outlet I may encounter. With the proliferation of public charging in the greater Portland area, this normally goes unused. It sits in my car's cargo area as a bit of assurance.

I hope this helps you understand the options and make a choice that works for you!