- Our EV experience has prompted a new way of thinking about our car use. We are coming around to the idea that our car is now just another mobile device with a battery – when you arrive home, plug it in!
If you live in a detached house, semi-detached house, or a townhouse with power available in the carpark, most of your car charging will be done at home. Not only will this be the most convenient charging location, it also provides the cheapest electricity for charging an EV.
Most electricity retailers are introducing an ‘EV Plan’, with cheaper electricity available during off-peak hours. Our AGL Night Saver EV Plan charges 8c per kWh between 12:00 am and 6:00am, which is when we do all our charging. If we have an urgent need to charge during the day we pay 34c per kWh, though the overall cost is reduced from this flat rate by our solar output on sunny days.
If you have enough solar panel output you may be able to charge your EV for no cost during the day, or a much reduced cost if splitting solar and grid input.
To put this in perspective, using fast chargers in shopping centres or highway service centres – DC charging – costs anything from 50c – 85c per kWh.
Charging from your home electricity supply – AC charging – requires an adaptor connected between your AC power supply and the car. This can be a portable ‘granny charger’ plugged into a regular domestic power outlet, or a wall-mounted connector wired permanently into your home’s electrical system.
AC charging is relatively slow….
DC charging is much faster than a home (or public) AC charger….
Ultra Rapid DC chargers can charge at rates of 150 kW or 350 kW, but many cars are not able to charge at this rate. You can still use one of these chargers, but your vehicle will throttle the charging current to suit its internal systems.
Public DC chargers will require you to have an account with the network provider, the charging process being accessed through an app on your phone. Some public charging stations may also be able to be accessed as a ‘guest’ by swiping a credit card before you begin charging.
The cost of the electricity from these public DC chargers is around 50c – 70c per kWh. Tesla Superchargers are over 80c per kWh, but not all of these chargers are available to non-Tesla vehicles. Check the Tesla app.
More EV charging info…
Your vehicle battery stores electrical energy, and supplies this energy as Direct Current (DC) electricity to drive the motor. It will continue to do so until the battery is discharged.
To recharge the battery you need to connect your vehicle to an external source of electricity, and the electricity has to be ‘massaged’ by a battery charger to provide the correct rate of both voltage and current to suit the requirements of the battery
The source of electricity for recharging the battery can be either:
- AC (Alternating Current) or
- DC (Direct Current).
AC charging is available from your 230V domestic power supply. If recharging your EV’s battery from an AC power supply, a built-in inverter in your car inverts the charging current from AC to the DC required to recharge the vehicle battery. Generally speaking, AC charging is very slow compared to DC charging, though the slower AC ‘trickle’ charging is better for longer term battery health.
- Your portable charger connected to an AC outlet at home supplies current at the rate of up to 2 kW. At this rate it will take at least 25 hours to fully recharge a 50 kWh battery from below 10% charge.
- A wall-mounted AC charging station installed at home (or a holiday destination) will supply current at 7 kW. At this rate it will take at least 8 hours to fully recharge a 50 kWh battery from below 10% charge.
You will also find AC chargers installed in some shopping centres, hotels, etc; possibly faster AC chargers, up to 22 kW – though not all EV’s AC-DC inverters can process this level of AC power. (Often 7 -11 kW is the maximum AC charge rate – check your vehicle specs.)
The AC charger in our EV also ‘equalises’ or ‘balances’ the charge of all the cells in the battery. This is important to maintain long term battery health.
DC charging delivers a much higher rate of electrical current, and will recharge an EV battery more quickly than an AC charging. A DC charger feeds power directly into the vehicle battery without requiring use of the vehicle’s internal AC to DC inverter.
- A DC charging station supplying current at the rate of 50 kW will take up to 1 hour to charge a 50 kWh battery from 10% to 80% SoC.
- A DC charging station supplying current at the rate of 75 kW will take up to 45 minutes to recharge a 50 kWh battery from 10% to 80% SoC.
- Some DC chargers supply current at the rate of 150 kW and even 350 kW, though not all EVs are able to charge at this rate. Check your vehicle’s specs for the maximum rate of charge.
- Most DC charging stations consider 80% – 90% as a full charge, due to the chemistry of Lithium batteries. Above 80% the rate of charge is likely to be considerably reduced, or tapered, by the vehicle’s charging system, meaning that a ‘full’ (100%) charge will take much longer. Some vehicles will automatically stop charging at a fast charger when the battery’s SoC reaches 80% or 90%.
- How long will it take to charge? As a rough guide, the kW charge rate of a DC fast-charger will deliver an equal number of kilometres for every 10 minutes charged – eg 10 minutes at 50kW will give you 50km of range, 10 minutes at 150 kW will give you 150km of range, etc. (Only if your car is capable of charging at that rate.)
Note: Slower (more gentle) AC charging is likely to result in longer overall battery life than regular fast DC charging. If a DC charging station brings your battery up to 80% you can top up the last 20% on an AC charger at home.
Battery charging basics
Batteries have a Positive terminal (Cathode) and a Negative terminal (Anode). When connected to a load – in the case of an Electric Vehicle, the motor – electrons flow from the Anode, through the motor (causing it to spin) and then back to the Cathode.
When all the ‘free’ electrons from the Anode have moved to the Cathode, the battery is discharged, or ‘flat’.
A battery charger forces all the electrons which are now resident on the Cathode back to the Anode, through the electrolyte within the battery. When all the ‘free’ electrons have been moved back to the Anode the battery is considered to be fully charged, and the discharging process can begin all over again.
An EV battery actually has multiple internal ‘cells’, each with its own Anode and Cathode, joined to each other to form one large battery. A regular 12V lead-acid car starter battery, for example, has 6 individual internal cells. An EV motor battery has anything from hundreds to thousands of individual internal cells, depending on the type of battery cells used – cylindrical or prismatic. Each cell type has its pros and cons in terms of manufacturing, weight, cost, etc.
There are a variety of EV chargers available to recharge your EV battery – from slow, ‘top-up’ AC chargers for use at home to very fast DC chargers at public charging stations. Whichever charger you use, the charger will need a cable with a suitable plug to connect to the charging socket on your EV.
AC and DC charger cables have different plugs for connecting to the vehicle.
Most EVs in Australia are supplied with a small (portable) AC charger as a minimum charging option, connecting to a standard domestic 10 amp power outlet. Portable AC chargers are generally referred to as Level 1 chargers. Wall-mounted AC chargers are referred to as Level 2 chargers.
AC chargers connect to an EV with a 7 pin plug, known as a Type 2 plug, which delivers charging current to the battery via the car’s built-in AC-DC inverter. This plug forms the top part of a CCS2 plug/socket.
DC charging is much faster, and what is often (though not always) available at larger public charging stations. These DC chargers are known as Level 3 chargers. They charge an EV via the two large pins at the bottom of a CCS2 plug (on CCS chargers), but also use the 7 pins at the top of the plug to communicate with the car.
CCS and CHAdeMO Connectors
In Australia most EVs have a CCS charging socket (Combined Charging System), combining Type 2 (AC) and DC charging sockets. CCS is a European standard.
In Australia CHAdeMO sockets are available on only three vehicles – Nissan Leaf, Mitsubishi Outlander PHEV, and Lexus UX300e. CHAdeMO is a popular charging connection in Japan.
The CCS socket appears to be becoming the preferred ‘standard’ charging connection across the world.
CCS connections are commonplace at public DC fast charging stations and on most new vehicles, due to their general versatility and charging speed.
Most new electric cars in Australia accept CCS plugs at charging stations, although all vehicles have a limit on their rate of charge, varying from EV to EV depending on their battery and internal charging system. Check your vehicle specs.
Charging levels – how long will it take to charge your EV?
Charging levels refer to the rate at which electricity is delivered to a vehicle. Level 1 and Level 2 are AC charging, and are dependent on the internal AC-DC inverter in your EV to convert the AC to DC for charging the battery. Level 3 is DC charging, which charges the battery directly, and is much faster than AC charging through the car’s inverter.
The Lithium batteries in EVs will have a longer life-span if regularly ‘slow charged’ with AC, rather than fast charged with DC.
When being fast-charged with a DC charger your battery will have a longer lifespan if it is only charged to 80% or 90% of its total capacity. When charging at a public fast DC charging station you may notice that the charging rate drops a little when the battery’s State of Charge (SoC) reaches 50%, and then again, more significantly, when it reachers 80%. (The extent of this tapering varies from vehicle to vehicle). Nor should your battery be completely discharged to 0% – your vehicle’s internal systems will most likely prevent this from happening.
The charging rate of your car’s Lithium battery isn’t linear. A discharged battery will recharge more quickly through the first 50% of its charge cycle, then taper off a little for the next 30%, then charge at a lower rate again for the last 20%. Combined with the life-span issues mentioned above, plan on charging your vehicle only to 80% when using a public fast charger – though you might continue to charge beyond this point at a slower rate if you have a long journey to the next charger.
- Note: It has become good etiquette at public charging stations to disconnect at 80% if others are waiting to use the charger.
As a rough guide, the kW charge rate of a DC fast-charger will deliver an equal number of kilometres for every 10 minutes charged – eg 10 minutes at 50kW will give you 50km of range, 10 minutes at 150 kW will give you 150km of range, etc. (Only if your car is capable of charging at that rate.)
Charging at home with an AC charger is your cheapest option (other than a free public charger) but at a slow rate of charge. It is a more suitable option if you need to charge the battery to 100% in preparation for a longer trip, and for ‘topping up’ the last 20% after using a public fast charger.
You can charge at home with a portable AC charger at around 2 kW per hour. Our experience is that this varies a little from car to car – some charge at 1.8 kW while others charge at 2.3 kW. (You can buy an energy monitoring ‘smart’ plug for around $25 that will provide this info through an app.)
A permanent AC wall connector installed at home (single phase, 32A) will charge your vehicle at around 7 kW per hour. We have a Tesla Wall Connector installed in our driveway – this adds around 42 kms per hour to our MG ZS EV battery. Wall connectors are priced from around $750 for chargers with a cable – eg: Tesla wall connector | Occular wall connectors. The cost of connecting these devices to your electricity network will cost anything from $500 to $900 (or more) depending on the location of your main electricity panel, the installation path from the panel to your garage / driveway, and other local factors.
With these issues of variability in mind, please consider the figures in the table below as only a reasonably rough guide…
Where to find a charging station?
AC Portable Charger – Plug in at home (2kW)
Your most basic, easiest to access, and cheapest charging option is at home, if you have access to an AC power outlet in your garage or driveway.
A standard domestic 10 amp AC outlet will charge your battery at about 2 kWh per hour.
Domestic electricity supply is billed by your energy provider – anything from 30c to 40c per kWh for peak rates, or less than 10c per kWh for off-peak rates.
If you have solar panels you may be able to access ‘free’ electricity, depending on your solar capacity and setup, and what other appliances are using your solar current during the day.
- Charge time for a 50 kWh battery from 20% to 100% at 2kW is approximately 20 hours.
AC Wall Box – Home or holiday destination (7kW)
The ideal option for home charging is an AC wall charger. This provides a faster charge than a standard wall outlet – around 7 kWh per hour. (Supply and installation is around $1500 – $1800.)
The electricity consumed will be billed at your electricity retailer’s supply rate – 35c to 40c per kWh doing peak hours, or less than 10c per kWh during off-peak hours. Most wall chargers have an option to schedule the charge time to suit your off-peak period.
If you have solar panels you may be able to charge your car for free, depending on the capacity and setup of your home electricity supply system. Some home chargers are able to choose between solar and grid power (see Zappi chargers).
Keep in mind that your solar panels may only be able to supply a percentage of the EV wall charger requirements – if you have a 4 kW solar system it won’t be able to supply 7 kW!
Some public or destination chargers (at holiday destinations and shopping centres) are also AC chargers, and charge at 7 kW (as above) or up to 22 kW if 3 phase power is available. However, your vehicle’s internal AC-DC inverter may only be able to operate at a maximum rate of 7 kW – 11 kW.
AC charging is relatively slow – though this slow rate of charge is better for the long term life of your battery, rather than constant, high-power ‘fast’ DC charging.
- Charge time for a 50 kWh battery from 20% to 100% at 7kW is approximately 6 hours.
DC Charging Stations – Highway stations, shopping centres (50kW- 350kW DC)
Faster public charging stations provide DC charging at rates of 50 kW, 75 kW, 150 kW, or 350 kW, and are slowly being rolled out across the country. These chargers require a payment through either a credit card or phone app. Most commercial fast chargers cost from 50c to 85c per kWh. If you are a member of a motoring organisation you may be able to access a discounted charging rate, if such an arrangement exists with the service provider.
Motoring organizations such as the NRMA have been installing 50 kW and 75 kW charging stations on major highways, and in some towns that the highway has bypassed. (This provides an incentive for travellers to stop off at some of these bypassed towns.)
The NRMA combined with other state motoring organizations – RACV, RACQ, RAC, RAA and RACT – to purchase the Chargefox charging network. A Chargefox station at a shopping centre near where we live has a charging rate of up to 350 kW – though I am not aware of any current EVs that are able to take advantage of this rate of high speed charging!
You will notice that when using a fast charger your charging rate may be tapered when your battery capacity reaches 50%, and further again above 80%, depending on the design of your vehicle’s charging system. Your EV may also have a maximum charging limit of 75 or 80 kWh, and the energy available from a high speed rapid or ultra-rapid charger will be throttled to suit your vehicle.
Shopping centres, clubs, pubs, and holiday destinations are also busy installing charging stations (both AC and DC) in an effort to attract customers.
- Charge time for a 50 kWh battery from 20% to 80% at 50kW is approximately 40 mins.
Find your nearest charging station:
Plan a trip with ABRP (A Better Route Planner):