By Finn Peacock – Chartered Electrical Engineer, former CSIRO, EV owner, founder of SolarQuotes.com.au
Whether you’re considering buying an EV, waiting for delivery, or driving an EV, knowing how (and how) they charge is an important part of ownership.
In this guide, I will discuss power (kW) and energy (kWh).Knowing the difference is important!People mix these up all the time – even electricians who should know better.
A typical gasoline car gets 10 kilometers of range from 1 liter of fuel.A typical electric car gets about 6 kilometers of range from 1 kWh of electricity.
For a petrol car, you need 10 litres of fuel to travel 100 km.At a very conservative cost of $1.40 per liter of fuel, 10 x $1.40 = $14 for 100 kilometers.
Note: Gasoline is over $2 per liter at the time of writing – but I’ll stick with $1.40 to show that EVs are much cheaper, even if the Russian dictator didn’t exaggerate fuel prices.
In an electric vehicle, about 16 kWh of electricity is required to travel 100 kilometers.If your electricity retailer charges 21 cents per kWh, the cost is 16 x $0.21 = $3.36.
Electric vehicles are less expensive to drive if you consider charging from solar panels or charging at off-peak rates based on time-of-use (ToU) tariffs.Let’s run some numbers to illustrate:
If you have an electricity bill of 21c and a solar feed-in tariff of 8c, the net cost of charging the car with solar energy is 8c.That’s 13c cheaper per kWh than charging an electric car from the grid.
Time-of-use tariffs charge you different rates for electricity based on the time of day you get from the grid.
Compare Aurora Energy Tasmania’s different electricity prices at different times of the day:
If you set your EV charger to only run on this ToU program with Aurora from 10am to 4pm, 100km of range will cost you 16 x $0.15 = $2.40.
The future of Australia’s electricity plan is time-of-use tariffs, the cheapest electricity during the day (a lot of solar) and at night (usually with plenty of wind and little demand).
In South Australia, you are charged a measly 7.5 cents per kilowatt-hour of the day during a time-of-use tariff that offers a “solar sponge.”
Some retailers also offer special EV tariffs where you can pay a lower per-kWh rate to charge your EV at certain times, or a flat daily rate for unlimited charging.
One last thing – watch out for “demand tariffs”.These power plans charge you a lower total electricity bill, but can get you into big trouble if your electricity consumption exceeds a certain threshold.Charging your EV with a 3-phase 22 kW charger could mean you pay 10x your standard electricity bill!
A basic EV charger is a very simple device.Its job is simply to “ask” the car if it can accept any charge, and if so, safely supply power to the vehicle until it’s told to stop.
An EV charger can’t power the car faster than the car asks for it (which is dangerous), but if you have some wisdom, it can decide to slow the charge down or based on other conditions – for example:
Home EV chargers are also AC.That means they didn’t do anything very special.They just regulate the kilowatts of 230V AC going into the car.
In fact, the electronics box you can buy to charge your car isn’t technically a charger.Because all it does is provide regulated AC power.Technically, the actual charger is in the car, converting AC to DC and taking care of all other charging tasks.
This onboard EV charger has a hard power limit on its AC-DC conversion.11 kilowatts is the limit for many electric vehicles – such as the Tesla Model 3 and Mini Cooper SE.
Nerd confession: I should technically call the device you plug into your car an EVSE (Electric Vehicle Supply Equipment).But that will confuse most laypeople, so at the risk of getting an angry email from a retired engineer, I call these devices “chargers.”
Dedicated high-speed public EV chargers are themselves chargers that feed DC power directly into the battery.They are not limited by the car charger because they don’t use it.
If your car can handle it, these bad boys can charge with up to 350 kW of DC.Note that they do have to slow down considerably when your battery reaches about 70%.Still, they can add 350 kilometers of range in just 10 minutes.
The industry has adopted terms to describe slow, medium and fast charging.Rather boringly, it’s called Level 1, Level 2, and Level 3 charging.
A level 1 charger is just a cable and power brick that connects to a standard power point.They charge at 1.8 to 2.4 kW from a standard household socket.
Pro tip: If your automaker doesn’t provide a mobile connector for your car, make sure you buy one and keep it in the trunk – it can save you a day of bacon even if you never use it at home time.
To illustrate what a Level 1 charge rate of 1.8 kW means – it will add 1.8 kWh per hour to your car battery.
1 kWh of power in an EV battery is equivalent to about 6 km of range.Therefore, a level 1 charger can provide a range of about 10 kilometers per hour.If you charge the car overnight (about 8 hours), you will add about 80 kilometers of range.
But level 1 can charge at a higher speed.Depending on the manufacturer, your device may have interchangeable plugs.
All portable EV chargers come with regular 10A plugs, the same as all other appliances in your home, but some also come with interchangeable 15A plugs.This has a wider ground prong and requires a special socket that can handle thicker wires at 15A.If you own a caravan, you’re probably familiar with them.
Some mobile chargers have a 15A “tail”.These are the 10A and 15A tail ends that come with the Tesla mobile charger in Australia.
If your portable charger is 15A on the end and you want to charge at home, you will need a 15A outlet in your car park.Expect to pay about $500 for this installation.
Nerd Fact: If your local grid voltage is high (should be 230V, but usually 240V+), you’ll get more power because power = current x voltage.
Bonus nerdy fact: Depending on the manufacturer, mobile chargers are typically limited to 80% of their rated current.So a 10A charger might only run at 8A, and a 15A device might only run at 12A.Combined with fluctuations in grid voltage, it meant that I couldn’t provide an accurate EV charging speed for the mobile connector.
Tesla Nerd Fact: Tesla mobile chargers imported after November 2021 can charge at a full 10A or 15A, depending on the tail used.
Pro tip: If you have a recent Tesla and are lucky enough to have a three-phase outlet in the garage, you can buy a third-party tail that can charge at 4.8 to 7kW (20 to 32A) using a mobile connector.
âš¡ï¸ âš¡ï¸ Charging Speed: Approx.Range of 40 km/h (single-phase) or up to 130 km/h (three-phase)
Level 2 charging requires a dedicated wall charger with its own dedicated wiring back to your power strip.
Level 2 chargers cost $900 to $2500 for hardware and about $500 to over $1000 to install.This pricing also assumes your power strip and mains can handle the extra load.If they can’t, upgrading your supply can cost thousands of dollars.
A single-phase 7 kW Level 2 charger can add about 40 kilometers per hour of range.If your car can handle it, a three-phase 22 kW EV charger will add about 130 kilometers per hour of range.
Nerd Fact: While 3-phase, level-2 chargers can put out up to 22 kW, many cars can’t convert AC power so quickly.Check your car’s specs to see its maximum AC charge rate.
This charger is completely DC and has an output of 50 kW to 350 kW.They cost over $100,000 to install and require a huge power source, so you’re unlikely to have one installed in your home.
Tesla’s Supercharger network is the most famous example of a Level 3 charger.The most common “V2″ supercharger has a maximum output of 120 kW and a cruising range of 180 kilometers in 15 minutes.
Tesla’s network of Supercharger stations gives them a competitive advantage over other EV manufacturers due to their location on popular travel routes, reliability/uptime, and sheer volume compared to other Level 3 chargers.
However, as electric vehicles become more common, other competing networks are expected to emerge across the country and improve their reliability.
Tesla Nerd Fact: Australia’s red and white “V2″ Tesla Superchargers are DC fast charging, typically charging at 40-100 kW, depending on how many other cars are using them at the same time.A handful of upgraded ‘V3′ superchargers in Australia can charge up to 250 kW.
Pro tip: Watch out for slow AC chargers on road trips.Some roadside chargers are slower AC types that may only charge from 3 to 22 kW.These can top up a bit when you park, but aren’t fast enough to conveniently charge on the go.
All electric vehicles sold in Australia from 1 January 2020 are equipped with an AC charging socket called a ‘Type 2′ (or sometimes ‘Mennekes’).
Post time: Aug-02-2022
