Ensure your home is ready for safe EV charging. Discover the best charging methods, safety features, and habits to protect your home and electric vehicle.
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Electric vehicles are quickly becoming our most power-hungry residential appliance; one that needs to be thoroughly understood in order to safely charge at home.
This isn’t a problem when charging at public EV charging stations designed for high energy draw, but most charging sessions are done overnight in the comfort of EV owners' homes; where supply and infrastructure to handle high-energy demand is limited.
With the addition of such a power-hungry appliance to your ecosystem, it's important to consider charging methods, safety features, and good charging habits designed to keep you and your home safe for years of charging to come.
Balancing your power draw
In New Zealand, houses commonly have a single-phase power supply with a maximum current rating of 63 Amps (A). This is the maximum amount of current that can be drawn at any given time. For reference, running your washing machine may draw up to 10A, a heat pump as much as 20A, or an electric induction hob even 32A.
Compare these appliances with the most common wall-mounted AC charger in NZ; a 7.4kW unit which can draw 32A by itself. You can see with just a few of these high-energy appliances running in tandem, you’ll quickly approach the maximum load your home can handle.
What happens if you reach or exceed your home’s maximum rated load? You'll likely blow the main protective service fuse at your boundary box or street pole. Not only is this a huge inconvenience waiting without power until a service person arrives to replace it, but your main circuit board may suffer from overheating before the fuse is overloaded.
Home overload protection
To avoid manually balancing your electrical load, you can consider installing a smart EV charger that offers home overload protection. This feature automatically slows or stops a charging session if your total power usage nears your building’s maximum draw. It does this by monitoring your home’s total power draw via a power sensor, so it can balance the quickest rate of charge with the power available to safely use.
It's a simple yet important electrical safety feature that’s part of all Evnex home charging installations.
Other, more manual options include electrical work: you can have a professional electrician install a 60A circuit breaker to protect the pole fuse from blowing if your main circuit does overload, or you get your electrician to set a lower limit for the total draw of your EV charger during installation.
How does it work?
During installation, an electrician will set a maximum current limit for the EV charger and fit a power sensor at the building’s switchboard to monitor the main house circuit.
The power sensor will read the total energy draw of the building 50 times a second to ensure it is not within 10% of its maximum rated limit. If the overall power demand of the home reaches this threshold while the charger is active, it will dynamically lower the rate of charge.
As your household power demand fluctuates, your charger will continue to adapt its rate of charge until either stopping the charge completely or returning to maximum speed when safe to do so.
It’s a handy tool that provides automated protection for EV drivers from accidentally overloading their main circuit.
