This guide is intended to contain all the information an ordinary driver needs to know about charging. Links to deeper technical information are also provided.
When do we charge?
Charging an EV is quite different from fuelling a conventional (Internal combustion Engine or ‘ICE’) car, so before discussing the technicalities of charging it’s worth considering when and where you are going to need to charge.
Charging is slower than fuelling but, if you can arrange for charging to occur while the car was going to be parked anyhow, it takes less of your time than pumping fuel. So when planning your charging, you need to think about how it will fit in your everyday routine rather than going to “fill up” from time to time. Instead of thinking about how you fuel your old car, think about how you charge your phone or laptop.
- Routine charging: for everyday driving needs. For most people the ideal is to plug in at home every night so you leave home every morning fully charged. Unless your daily mileage is unusually high, this means you simply don’t need to worry about charging at all for your day-to-day driving. Charging overnight means that you can take advantage of off-peak electricity prices that are available in most areas (“Economy 7” in the UK, Time of Use (ToU) plans in the US). Finally, being plugged in before you start driving in the morning means you can heat or cool the car using mains power rather than depleting your battery.
- En-route charging: to reach a destination which is beyond the range of a single charge. This is the one case where you might be hanging around waiting for a charge so speed of charging is critical. If the charger is fast enough you can get most of the charging done during the meal or coffee stops you would be making anyhow, but slow public charging can be so slow/unreliable as to make the journey impractical. Tesla Superchargers are the the only practical option for very long journeys (and the ideal for any journey), but rapid public charging is a viable option for many routes that aren’t yet served by the Supercharger network; particularly trips that are only slightly beyond single-charge range from home.
- Destination charging: to cover your local driving while you are away from home or to give you the charge to get home again (or to a charger). This is often the most problematic. On the one hand, slow charging may be perfectly adequate – after a long drive you are presumably going to spend a reasonable time at your destination – but on the other hand the public charging infrastructure is currently far from ideal in most areas. If you are able to choose to stay in hotels which have charging facilities then that can help a lot, but otherwise you will end up using improvised or inconvenient charging arrangements and always need to have a “Plan B” in mind. Some people regard this as too much trouble and choose to take a rental car (or plane, train etc) for destinations beyond easy reach using Superchargers, while others enjoy the challenge of planning a convenient route through inhospitable territory. Most owners are prepared to put up with a little inconvenience on occasional trips ‘off the beaten track’ in exchange for day-to-day charging that’s actually easier than fuelling an ICE.
Moving a car requires very large amounts of energy, regardless of whether that energy comes from petrol, diesel, electricity or something more exotic. Whenever you are handling that much energy there is always the safety risk of some kind of fault or mistake allowing the energy to escape – BOOM!
If you charge your electric car using a permanently-installed chargepoint that was competently designed and installed then it is extremely safe and reasonably ‘fool-proof’. If you have to use something else, then the risks are higher and you should treat it with caution; just like fuelling an ICE from a spare can needs more care than going to a filling station.
Using portable equipment built for charging and following the manufacturer’s instructions is still fairly safe, but as you start to use adapters and extension leads you need significant skill and knowledge to tell whether something that appears to work is actually safe.
If you are not absolutely certain, avoid leaving improvised charging arrangements unsupervised (particularly at night).
Units and terminology
You need to be aware of the various terms used on the displays of your car and charging point listings. Whilst some of these terms may be familiar from elsewhere, some are EV-specific.
Kilowatt-hours (kWh) is a unit of energy and is used to display how much charge you have taken on board, or have used up when driving. Your Model S has a 60kWh, 70kWh or an 85kWh capacity ‘fuel tank’ (depending on model). Your home electricity bill is also measured in kWh.
Kilowatts (kW) measures how fast you are charging (or using up your charge). Charging for an hour at 1 kW will give you 1 kWh of charge.
The car can also display the charge in the battery as the number of miles (or km) of driving that it will deliver. This conversion is imprecise – if you drive faster or more aggressively, you will use more ‘fuel’ and so get fewer miles from a ‘full tank’. The car’s estimate can be set to give a ‘best case’ or ‘fairly realistic’ estimate (variously called ‘typical’, ‘rated’ or ‘ideal’ depending on your region), but in either case it does not take account of your driving history or other factors. If you want to make a similar estimate yourself, 1 kWh is worth about 3 miles (or 5km).
Wh/mile (or Wh/km) is your ‘fuel consumption’ figure. Smaller is better; typical is somewhere around 300 (Wh/mile) or 190 (Wh/km).
Volts (V) are a measure of the strength of an electrical supply and Amps (A) measure how much electricity of that strength is flowing. Either on its own is not of much use: multiply the two together and divide by 1000 to get the power in kW, which is what you usually want to know.
Three-phase is a technique to get more power out of a given size of cable by using three small circuits rather than one large one. Tesla vehicles supplied in North America or Japan can’t use three-phase supplies for charging. The display in the car of V and A shows only one of the three circuits, so you need to multiply by 3 if the supply is three-phase (shown by a stylised 3 symbol on the display).
An EVSE is a piece of safety equipment, needed between the car and the electrical supply. You can have a portable EVSE (such as the Tesla Mobile Connector) – a cable with a ‘lump’ in it – which is used for charging from ordinary power outlets, or the EVSE may be permanently installed (such as the Tesla Wall Connector or a public chargepoint). An EVSE is often (incorrectly) referred to as a ‘charger’, whereas the charger is actually internal to the car, so ‘chargepoint’ is a better term to use for the thing on the wall.
Superchargers are Tesla’s very high-speed charging stations, which are gradually being installed throughout countries where Tesla vehicles are sold. Where available, they are the best possible option for charging away from home.
CHAdeMO is a charging connector/system developed by Japanese manufacturers. You can use them if you buy the optional CHAdeMO adapter from Tesla. They offer the fastest charging available other than Superchargers.
CCS is a charging connector/system similar to CHAdeMO, favoured by BMW and VW among others. You can’t use these charging connectors with Tesla vehicles, although they are often found in charging stations with multiple connectors – like fuel pumps with one hose for diesel and another for petrol – and you will be able to use one of the other ones.
Slow, Fast, and Rapid chargepoints Unfortunately, although widely used, these have become meaningless marketing terms. You need to look at the chargepoint’s rating (in kW or Amps) to know how fast it is.
AC and DC These ordinary electrical terms have special meaning for car charging: for practical purposes, DC means ‘fast’ (such as Superchargers) and AC means ‘normal’.
The Tesla charge port
The charge port is concealed behind a cover in the left rear lamp cluster. To connect a charging cable you need to open it by either:
- Selecting the charging page on the main touchscreen and pressing the ‘open chargeport’ button, or using the similar button in the smartphone app.
- Using a dedicated button on the plug of Tesla-supplied charging cables and Superchargers (not available on ‘standard’ cables)
- Pressing and holding the rear button on the keyfob (the part which is double-clicked to open the tailgate).
Domestic chargepoints, Superchargers and Tesla charging connectors start charging automatically as soon as you plug them in. Commercial charge points, however, often need to be started manually and often require identification with a smartcard. The controls on these commercial chargepoints are often very poorly designed and hard to understand: They may require cables to be connected in a specific order (before/after using the smartcard), and may also require you to ‘sign out’ with your smartcard at the end of the session.
Once a charging cable is connected, it is automatically locked to the car. To remove the cable, you unlock it:
- From the touchscreen or smartphone app.
- Using the dedicated button on Tesla-supplied plugs, and also the button on standard type1 plugs (N. America). Not available on standard plugs in Europe.
- Double-clicking the main button on the keyfob when the car is already unlocked (or double-click twice if locked).
Charge connector – North America/Japan
The Model S in these markets has a Tesla-specific connector. Tesla supplied charging equipment – the UMC mobile connector, the Wall Connector supplied for home use and found at some hotels, and Superchargers – plugs directly into the car. Other public AC charging uses the ‘J1772’ connector (also known as ‘type1’) and in this case a small adapter – supplied with the car – is needed to connect the cables from such chargepoints. An adapter is also available at extra cost for use with CHAdeMO chargers. All public chargepoints in these markets have cables attached – only the adapter is needed to connect to the car.
Charge connector – Europe/Australia/China
The Model S in these markets has a version of the standard ‘type2’ connector, which is widely used on other vehicles and public charge points. Tesla-supplied charging equipment also has the standard connectors. Some public charge points (and all Superchargers) have type2 cables attached and so plug directly into the car whilst others have only a socket and expect you to bring your own cable (so you will need to carry a ‘type2’ cable to use them). A very few public chargepoints (and some private ones) have a type1 connector permanently attached: unfortunately you cannot use these points to charge a Model S. An adapter is available at extra cost for use with CHAdeMO chargers (note that this is not the same as the N.America version CHAdeMO adapter).
CHAdeMO connectors – Warning!
The capability to access CHAdeMO rapid charging points using the optional adapter is extremely useful, but to do so you will have to handle the CHAdeMO plugs fitted to the charge points. There are several different designs in common use – the best are merely awkward, while the worst are unbelievably bad – even those with an engineering background and fore-warned of the issue have struggled on their first encounter with one particular type of CHAdeMO connector. It is worth noting that this isn’t a problem specific to the Tesla adapter – Nissan drivers have the same issues connecting these chargepoints to their cars.
The issue is that the connector must be securely locked into the adapter: If it is not, the charging will not work, and instead of saying something useful like ‘connector not locked’, these units typically pause for a minute or so and then give an error such as ‘communication failure’. The best style of connector simply push into the adapter and lock automatically, with a large button on the back that is pressed firmly to release. Other styles have two buttons – one to lock, one to release. The problematic connector has an unlock button on top, but also has a long lever on the bottom. This style pushes into the adapter with a ‘click’ and appears firmly latched but it will not actually work unless you pull the lever in towards the handle, and hold it there with a little rubber boot that slips over the end of the lever. The same problem occurs in reverse when trying to remove the adapter after charging: Pushing the release button has no effect unless you have already freed the lever from the rubber boot and pushed it away from the handle.
Understanding charging rates
There are many factors affecting the precise charging rate you will get and only the key ones are presented here. For full details, or if you don’t get the rate you expect, see the article Understanding charging rates.
The most precise way to describe a charging rate is in kW. However, you can also describe it as miles of range per hour of charging (MPH), when 1 kW is approximately 3 MPH. Beware that if you have the display in the car set to show MPH rather than kW, the MPH figure is an average during the whole session and so can be misleading if the charging rate has changed (especially so at Superchargers). By all means use the MPH figure if you find it helpful, but if reporting a problem make a note of the kW (or the V and A if kW is not shown).
Normal AC charging
Charging will be at a constant rate throughout the charge, except for the very beginning and end. If your car has only a single charger then the maximum charging rate is 11kW (Europe) or 10kW (N,America) – about 30 MPH- but if your car has the optional second charger then the limit is doubled to 22/20kW, 60 MPH. Subject to that limit, you will get as much as the charging station offers.
In Europe, common rates are:
|Domestic Socket||Anywhere||2.3 kW||7|
|32A single phase||Home(UK)/public||7 kW||20|
|16A three phase||Home(non-UK)/public||11 kW||30|
|32A three phase||Public chargepoint||22 kW||60||Limited to 11kW / 30mph if single charger|
|63A three phase||Multi-standard rapid||43 kW||60||Model S can’t use all the power available|
In North America, common rates are:
|Domestic Socket||Anywhere||1.4 kW||4|
|30A chargepoint||Public charging||7 kW||20|
|NMEA 14-50||Home, RV parks||10 kW||30||Use with UMC|
|Tesla HPWC||Home, Hotels||20 kW||60||30 if single charger|
Supercharging is extremely fast when the battery is empty but slows down as the battery fills up. Once the battery is over 90% full it is little faster than many normal charging stations. The intended mode of use is to arrive near to empty, charge only until you have comfortably enough to reach the next Supercharger, and then drive on. You can get a full charge at a Supercharger, but it will take much longer (about 90 minutes).
Superchargers are normally installed in pairs, with the stalls labelled 1A, 1B, 2A, 2B etc. Power is shared between the ‘A’ and ‘B’ stalls, so that if both are in use the maximum power to one car is reduced. If you arrive at a Supercharger which is not busy, try to use a stall where the other one of the pair is not in use: If there’s another car in 1A, try to use 2A rather than 1B. If you have no choice (all stalls are taken or it’s only a 2-stall site in the first place) then be prepared for a slightly longer charge time; perhaps 10 or 15 minutes extra.
CHAdeMO public charging stations offer an intermediate option – they are faster than the fastest AC charge points but slower than Superchargers. Like Superchargers, the charging rate is not constant, although the variations in speed are not so dramatic. CHAdeMO does not use your on-board charger, so does not matter whether you have single or dual chargers. In Europe, it is common to find charge points described as ‘AC/DC’ with two or more cables – one Type2 plug (AC) and one CHAdeMO (DC). Although the Type2 connector conveniently plugs directly into the Model S, you will always get a faster charge (usually, much faster) by using the optional adapter to connect to the CHAdeMO cable instead.
The best CHAdeMO chargers are advertised as ’50kW’. These will charge a Model S at 43kW when empty, rising gradually to 48kW at about 75% full, then gradually reducing to about 30kW at 90% full – equivalent to somewhere around 135MPH on average.. Some manufacturers’ ’50kW’ units are marginally slower than this.
Some CHAdeMO stations are advertised at a lower rate, commonly ’25kW’, because the owner has either selected cheaper equipment, or does not have sufficient power available to run at full rate. These stations will deliver a fairly constant rate throughout the charge – perhaps 75MPH for a 25kW unit. These reduced-power stations are relatively rare in most areas at the time of writing (2015), although relatively common in Japan.
There is another category of station, manufactured by Nissan/DBT, which are advertised as ’50kW’ but actually have a maximum output of about 42kW and have design flaws such that they tend to overheat if used at full power for a long period. Tesla have arranged for the car to detect these stations and charge at full power for up to 30 minutes (delivering about 60 miles of charge in that time); after that, the car reduces the charging rate to about half of normal for so long as you remain connected. These stations also have a poor reputation for general reliability (even when charging Nissan vehicles), and it is anticipated that Nissan/DBT will eventually upgrade or repair them to solve this problem. In the meantime, it may be preferable to make two shorter stops rather than one long one.