So You’ve Bought Another EV – Do You Need Another Charger?

As the petrol crisis encourages more and more Australians to go electric, we’re increasingly seeing the rise of the two+ EV household. So how do you go about charging two cars?There’s no straight answer to charging an EV because what works for you won’t always work for your neighbour.

However if Mum and Dad have both gone electric recently, it’s reasonable to ask how to manage fuelling everyone’s mobility. If employment, cheap electricity and after-school sport schedules aren’t very flexible, getting your car charged could be a challenge.

But there’s more than one way to skin a cat, and with any luck you won’t need to spend $1500+ to double up on the wiring.

Electric Vehicle Supply Equipment

In the eternal war of jargon against useful communication, the techno babblers have decided EVSE is how we should describe car-charging hardware. Common terminology might roll off the tongue better but “car charger” is so general it can become confusing.

In reality these things are a glorified extension cord, but if you’re new to electric vehicles, it might be worth reading some of our Frequently Answered Questions because we’ve been helping people and writing up the examples for years now.

There’s 3 basic types:

1. The “granny charger” which just plugs into any one of a few million power points anywhere in the country.
   They’re the slow but universal device that doesn’t always come as standard with your EV.
2. Type 2 AC charging which many people have at home or you’ll find in car parks for shops, wineries, motels etc.
   They’re the medium speed “destination chargers” which you may need to bring your own cable to use.
3. DC chargers featuring a big heavy cable that’s always tethered to the station. Usually found in public fast chargers, these can put out enough electricity to power 20 houses at full load, which means you can be back on the highway in about 20 minutes. While smaller DC chargers are available, there’s seldom a good use case or budget for them at home.

Granny Is Good

Last I checked, the majority of Australians are applying the KISS principle¹ to EV charging – they’re just using a standard power point.

Plugging in and trickling 2kW (or about 15km range per hour) appeals to tight arses like me and provided you’re not doing astronomical mileage, it works pretty well.

In the case of multiple cars, the challenge might be reaching the second car with the length of the car charging cable – using an extension cord isn’t out of the question, provided you’re careful.

You can also add a some basic smarts by switching the granny charger on or off using a timer to align with a “free hours” retail deal or a sunshine circuit to harvest solar. For a retiree or stay at home worker who does the school run, you’d need little else.

Proper Charging

A type 2 AC car charger is really what we should be aiming for in every driveway or daytime parking space.

• Reliable, fit for purpose, secure and weatherproof connections
• Properly controlled by the network for grid stability in times of emergency
• Automatically set to best use your own solar

Perhaps the best motivation for a proper AC charger is economic. It’s in your best interest to make use of whatever retail tariff you have available and having a charger you can program gives you the ultimate power.

As with granny chargers, one challenge with sharing a type 2 EVSE between multiple cars is that some with their own tethered cables aren’t long enough to reach the second car. Get an untethered EVSE so you can buy a charging cable long enough to reach both without having to pull cars in and out.

Having a cable long enough to reach both cars in a driveway is priceless.

Juicing The Grid

Before thinking about a second charger, you want to look at how much power you have available. Electric vehicles are the biggest load you’ll ever plug in at your place and they can tax the connection you have with the grid.

For example, 80% of Australia’s east coast has a single phase supply. While old houses may have only 32 Amps, or perhaps Victorian homes with a gas connection could be 40 Amps, the standard capacity is 63 Amps.

63 Amps multiplied by 230 Volts means your typical house has 14.5 kilowatts available, and two EVs could use all of that power, leaving nothing for the rest of the house.

Most EVs start at 7kW of charging capacity, and if you have 3 phase that can jump to 11kW or 22kW.

Sharing Your Power

Whether you have one EVSE or more, what you really need is smart hardware that dynamically controls charging power so you never overload a circuit. Or at very least a smart installer who can set the maximum charging rate with a hard limit.

“Powershare” is what it’s called in Tesla terminology. Imagine you’re cooking tea, air conditioning and charging your house battery, these could be 2kW + 2kW + 5kW loads respectively. Consumption (and possibly solar generation) would bounce around from minute to minute, but the EV charger needs to soak up what it can without going over 5.5kW and blowing the service fuse.

Sharing A Circuit

If you have an EV charger, using 10mm² cable or more, protected by a 40 Amp breaker, there’s some headroom in the circuit design to reliably run a 32 Amp/7kW EVSE.

You should be aware that many sparkies, and even massive hardware chains have underspecified 6mm² cable for this job, and it’s really sailing too close to the wind.

However the same sharing concept can be applied to give you two EV charging sockets on one 40 Amp rated sub circuit, and the advantage is of course a lower installation expense and better utility.

A post from the Electric Vehicles for Australia Facebook group offers an idea, but it would probably be best if each EVSE had their own circuit breaker in a small sub board enclosure, though industrial plugs make sense in some applications.

Most EV chargers I’ve dealt with can be dialed up or down to suit standard circuit ratings, ie 6, 10, 16, 20,25, or 32 Amps. So during commissioning you can choose a combination that keeps the total load below 40 Amps.

I always advise that the best EV charger is one that’s tied into your solar, or particularly your home battery system. Having it all under the same brand ecosystem and monitoring app gives you visibility plus the best chance of getting everything to play nicely together, because draining your home battery into the car isn’t usually the best outcome.

Weigh Up Speed, Convenience And Expense

If you have a small roof and an appetite to use cheap grid electricity through a limited time window, getting a 3 phase connection can be a great advantage. When the special 3 hours of power tariff is available, you want to be able to suck it down quickly, and the same principle applies to having a big solar power system. The old adage rings true, make hay while the sun shines.

Your EV might also make the choice for you; say you have a 3 phase supply:

• The BYD range generally has a single phase on board charger
  – so Mum’s car could have 20 Amps (4.6kW) made available to it.
• Dad’s 3 phase Cupra could be dialed down to 16 Amps
  – across 3 phases that’s still a healthy 11kW

I’m great at spending your money, so of course I’ll recommend the best performance package. If you’re not so keen on overkill, but really value reliability, two EV charging sockets on the same supply, configured to share the available power, might just be the ticket to durability and domestic harmony, because nobody wants to be playing shuffle shenanigans in the driveway at midnight.

If you’re thinking of investing in a home EV charger, whether it’s your first or second, take a look at our dedicated home EV charging guide for some tips.