A three pin lead, widely called a granny charger, plugs into an ordinary domestic socket at one end and into your car at the other. There is no wall box and no installation: the box partway along the cable does the work a charge point would normally do.
It is the slowest way to charge a car and the most universally available, which is exactly why it is worth owning even if you have a wall box at home.
What varies across the {M} range
The power is about 2.3 kW, which is a ten amp draw from a thirteen amp socket. That deliberate margin is the point: a domestic socket and its wiring were never designed to run at their rated maximum for eight hours without a pause, and pulling the full thirteen amps overnight is how sockets and fuse holders get hot.
At 2.3 kW a plug-in hybrid battery fills overnight comfortably. A large electric car does not, and would need most of two days from empty, so treat a three pin lead as a top up or a fallback on that kind of car rather than a charging plan.
The only choice to make is which end goes into the car. Type 2 covers almost every car registered since about 2014; Type 1 covers the older ones. Counting the pins in your socket settles it in seconds.
Where a granny charger earns its keep
Three situations. Staying somewhere without a charge point, where an outdoor socket is the only option. A rented house or flat where installing a wall box is not yours to authorise. And as the lead that lives in the boot for the week your wall box develops a fault, which is the use nobody plans for and everybody is glad of.
Use an outdoor rated socket where you can, do not run one through an extension reel, and unplug at the wall rather than at the car when you are finished.
The build, and where to look next
The cables themselves do not vary by car. Tinned copper conductors, IP67 sealed moulded ends, a jacket that does not go stiff in winter, two years of warranty, free next working day delivery.
About 2.3 kW, which is a ten amp draw. That fills a plug-in hybrid overnight and would take most of two days on a large electric car.
Why not thirteen amps instead of ten?
Domestic sockets and their wiring were not designed to run at their rated maximum for eight hours at a stretch. The margin is deliberate and it keeps the plug and fuse holder cool.
Do I need Type 1 or Type 2?
Type 2 for almost any car registered since about 2014, Type 1 for older cars. Count the pins in your car socket: five is Type 1, seven is Type 2.
Can I use an extension lead?
No. Plug it directly into a socket, ideally an outdoor rated one, and never through a coiled extension reel.
Is it worth having one if I already have a wall box?
Yes. It is what you use away from home and the week your wall box stops working.
