You’ve probably heard a lot about charging electric cars, how slow or fast, how cheap or expensive, how simple or complicated it is. We’re here to explain how you can go about selecting the right sized charging station for your home and, we’ll explain all the jargon and just why this sentence is incorrect!
This weeks article will focus on the US home charging options and we’ll cover Europe in a follow up article.
In the coming weeks we’ll be publishing some hands-on reviews as we install and set up some different charging stations in our own garage before reporting in on how the winter treats them.
Let’s break down some terms:
Charging: The simplest term! This is the act of re-filling your batteries with energy. It’s worth defining because it only happens whilst the batteries need charging. Once charged, charging stops and so does any electricity flowing into your car. Some cars and chargers can switch charging on and off at different times of the day to take advantage of cheaper rates or cleaner electricity.
Charger: Almost everyone calls the box that goes on the wall the ‘Charger’ and this is a common misconception but, we all say it from time to time. The charger is in fact, to be found inside the car along with the seldom mentioned, Battery Management System. Together, the Charger and the BMS inside the car take current from the socket on the side of the car, amplify its voltage and split out the current to each of the battery cells to give each one the optimum charge.
Electric Vehicle Supply Equipment: or, EVSE is the real name for that box that hangs on the wall and connects to the car. Its job is to co-ordinate and switch on & off, the electricity supply to the car in a safe manner. When connected to the car it reports how much electricity is available and carries out checks to ensure that there are no electrical problems. It’s essential to the process and whilst fairly single-purpose, there are some models that add extra features like usage reporting and time-of-day controls.
SAE J1772: The roll-off-the-tongue name for the standards implemented in the EVSE and the charger on-board the car. It covers the rules and language used to communicate between the wall unit and the car and, the design of the plug that goes into the car. The plug is often referred to as a J1772 plug but you can call it a J-Plug, everyone does!
Volts, Amps and Watts: Electricity is dispensed using a host of terms. Voltage, current and wattage. We’ll cover what you need in detail later but, suffice it to say, the bigger numbers mean faster charging.
Time-Of-Day: Some power companies offer lower rates for electricity used at night. By charging at those times, you might save some money. That said, you can usually reduce your environmental impact by charging off-peak, between midnight and the early hours when there is a surplus of available power from something called ‘Base Load’. Either way, charging at night is always a benefit.
Pre-conditioning: Pre-conditioning is a feature that most electric cars have that allows you to pre-program heating or cooling to take place before you embark on a journey – when you pre-condition before a journey, you can save money and increase your range whilst enjoying a warm or cool car from the get-go. To support pre-conditioning, you’ll need a 240V wall unit – more to follow.
What do you want?
A charged up car each morning! To do that you’ll need to think about how much you’ll need to recharge each night. If you’re bringing the car home each night with an empty battery or you need a quick recharge, you’ll need the most powerful solution that your car supports but, if you only drive a few miles each day or week, you may only need a low cost, even free solution.
Another consideration is the features in the unit. Do you want a basic, plug-it-in-and-it-charges solution or something more sophisticated that can report usage, allow you to set time-of-day charging or even text you if you’ve forgotten to plug in?
The good news is that, even the most powerful solutions can now be installed at home with little more skill than some basic DIY – if you can hang a picture, you can install your own EVSE!
What do you need?
All cars today have a standard home charging connector, a J1772 socket. The only exception is the Tesla Model S & X that comes with an adapter. Tesla Motors has its own range of home charging equipment that fits directly into the Model S or X but, importantly, their unit can only be installed by a licensed electrician.
So, we’re shopping for a standard unit with a standard connector – that makes things easy!
The next puzzle is to figure out what size unit you need to meet your charging needs. If your charging needs are lightweight, perhaps you only drive a few miles per day and you don’t need pre-conditioning, the charging cable or EVSE that came with your car, that plugs into a regular 120V outlet, may be more than enough for your needs. If you’d like to charge faster, use pre-conditioning or would just like the convenience of a plug ready for you when you get home, you’ll need a bigger unit.
Bigger units almost always mean a wall mounted unit connected to a 240V supply.
This is where we need to start getting technical. We’re going to look at the amount of current that the wall unit supplies and the amount of current that the car can accept. The amount of current is measured in Amperes or ‘A’ for short. Think of it like water flowing in a hose pipe, the more the current, the faster the car fills up. Solutions with higher current do cost a little more but, in most cases, they’re worth the extra… if not today, one day you’ll need more.
How much does your car accept?
Most cars fall into two charging levels: 16A or 30A. Some take more, 32A, 40A and even 80A. The more the car can accept, the faster you can charge it. Once you know how much electric current your car can accept, you can decide on the size of the wall unit.
How much can the Wall Unit supply?
Different wall units come in different current levels from 12A to 32A and even higher in more specialized cases.
Buying a unit that supplies more than your car needs can future-proof your investment but it’s important to realize that connecting a car that accepts 16A to a wall unit that can supply 32A does no harm… though it doesn’t speed things up either, the car will only draw 16A. Plugging a car that accepts 32A into a wall unit that offers 16A won’t cause an issue either but again your recharge rate will be limited to 16A.The speed that you can charge is limited to the slowest link in the chain.
What do these numbers really mean?
OK, we’re throwing out numbers like 32A and 240V but what does it really mean? Well, let’s put it in terms of how quickly we can charge. At the end of the day, that’s the most important thing right? Can I recharge in time for the morning? The time taken to fully charge depends upon both the size of the battery and the rate of charge but the speed at which we can charge is fairly similar across different cars and we can measure it in “Miles-per-hour”, that is, how many miles of range can we add in each hour of charging.
Here are some examples:
- Using the charging cable that came with the car: 3-4mph
- e.g. A Smart Electric Drive will recharge from empty in 14-16 hours
- 16A Wall Unit: 10mph
- e.g. A Nissan Leaf will recharge from empty in 8-10 hours
- 32A Wall Unit: 20mph
- e.g. A BMW i3 will recharge from empty in 4-5 hours
Most wall units can be used inside or outside but it’s always good to check with the manufacturer first if you’re installing outside plus, you’ll need a shrouded outlet too. The best location is a garage or car port, even if the car is outside as many are available with long cables, often up to 25′.
Hardwired or plug-in?
The last question comes down to how you want to connect the wall unit to the electricity supply. Once, all units where hard-wired; that’s where you run a power line straight into the unit – this has to be done by a licensed electrician and, with appropriate permits and inspections – no fun!
Today, all units are available in ‘Plug-In’ versions. That means that you can use an existing high voltage outlet or have your electrician install an outlet for you. Installing an outlet is far easier to complete by your electrician in terms of any permits or inspections and far cheaper. What’s more, you’re left with a simple outlet that you can plug in to, or unplug if you have problems.
We recommend purchasing a plug-in unit.
The cost of installing an outlet can vary a great deal depending upon the location of the outlet and the length of the run to the nearest electrical panel. Installation starts at just a few hundred dollars.
One word of warning: When having an electrician install an outlet, be careful to ensure that it’s placed directly under the location where you plan to install the wall unit. The cables on the wall units are usually very short.
What kind of outlet should I install?
Wall units require one of four common types of outlet – there’s three more but, they’re usually one of these four:
Note that the 14-30 & 14-50 can cost a little more to install as the cable they need is a little more expensive.
Selecting the unit and installation
Now you’ve figured out how much your car can accept and what size wall unit you want and, what features that you’d like you can begin shopping. We’ve selected a recommended group here offering a range of options.
Units start at just $395 for the ClipperCreek LCS-20P – A 15A unit with a NEMA 14-30 plug. It’s only 15A but is perfectly capable and known to be very reliable. For a higher power unit with a 32A capacity, the ClipperCreek HCS-40P moves to a NEMA 6-50 plug and has a 25 ft cable. At 32A it’ll charge your car at twice the rate of the 15A unit if your car can accept 30-32A.
There are also units with features like built-in room lighting, the General Electric WattStation 30A unit is large and imposing.
For a higher power option, there is the JuiceBox 40A Home Charging Station with 20-foot cable and a NEMA 14-50 plug. This unit offers plenty of overhead for cars that accept 32A like the BMW i3 or the Toyota Rav4EV that accepts 40A.
For those that find that they have only a limited supply to their charging location, the Siemens VersiCharge is an interesting option – it can be adjusted to limit the current where the wiring isn’t up to the full 30A available.
If you’d like to add some fancy Internet connected fun, the $549 ChargePoint Home 25 32A is an interesting choice. It comes as a wall unit without cable! The cable is sold separately at different lengths and it’s design has already impressed us:
Each of the units above can be installed with little more than a few screws and perhaps an electric drill.
We’ll be covering the installation of each of those units in the coming weeks but, (spoiler alert) you mostly, just plug them in.
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