Charging an Electric Car with a Cable from the House: What If the Socket Is Far from the Car?

The first discovery most new EV drivers make at home is this: there is electricity and there is a socket, but the place where the socket sits is not the place where the car parks. The socket at the back wall of the garage, the garden lighting circuit, the riser at the entrance of the building… The question always arrives in the same shape: can I charge the car with a cable run from the house? The short answer is yes, but it depends on where you extend. And most of that decision is made not when you buy the cable, but when you choose the unit.

Measure first: the real distance is not a straight line

The first step of this job is a tape measure. What you measure is not the straight line between the socket and the car, but the path the cable will actually follow: along the wall, around the door frame, around the side of the car. Neither end is fixed either — depending on the model the charging inlet sits on the front wing, the rear wing or the front panel, and the car may not park facing the same way every day.

• Measure from the socket to the car's inlet along the path the cable will follow; a straight-line distance is misleading.
• Check which side the car's charging inlet is on; reaching a socket on the right from the left adds several metres.
• Allow for the days you park the other way round; the longest case is the one that decides.
• You want the cable to hang with an easy curve, not under tension; a taut cable loads both the connector and the socket.

The right answer is not extending the cable but choosing the right length

On a portable charger the cable is a single piece from the plug to the car connector; there is no joint in the middle and the control box sits on that same run. That is why the cleanest answer to a distance problem is not to extend the cable afterwards but to buy a long enough unit in the first place. All three Bemis portable families are produced with different cable lengths:

Choosing one step above the distance you measured is the right call in practice: if you measured 6 metres, take the 8-metre version. Spare cable can be coiled up, missing cable cannot be fixed.

Why is a household extension lead or cable reel not the answer?

The first idea that comes to mind is to plug the unit into the extension lead you already have at home. But household multi-way adapters and cable reels are not designed for a steady, high-current load that lasts for hours: the contact point between plug and socket heats up, and a cable still wound on its reel cannot shed the heat it produces. We covered this in detail in our charging extension cable guide; the short answer here is clear: household extension products are not suitable for this job.

If you genuinely have to extend: an industrial CEE extension

In some cases even the longest version of the unit is not enough; the socket is inside the house and the car is at the far end of the garden. In that case the extension is made on the socket side, not on the cable that goes to the car: an industrial CEE extension cable, with a cross-section chosen for the current you will draw, goes between the socket and the plug of the unit. We collected the choice of cross-section, connector type and IP class in a separate guide — on long runs the cross-section is the variable that decides whether the cable will heat up.

Does the current have to come down as the distance grows?

Every added metre raises the resistance of the run; as resistance rises the voltage drops and the cable heats up. There are two practical consequences: you take less power at the same current, and the run gets hotter. The right answer is to bring the current down to what the run can carry. On the Pro Mobile 2 the charging current is set in six steps — 6/10/16/20/25/32 A — from the mobile app or the button on the unit; Mini Mobile offers two steps at 10A/16A and Mono Mobile two steps at 16A/32A. On a long run, dropping one step is better than straining the run and better than not charging at all.

Which socket will you plug into? That is what really decides the unit

After distance the second question is the socket itself. The type of socket at home draws the limit both of the power you can take and of the unit you can buy:

A plug converter also comes in the box of the Mono Mobile and the Pro Mobile 2, so you do not have to change the unit when the socket at home differs from the socket where you are going. A carrying bag is standard in all three families.

If the cable is going to stay outdoors

On a run that stays in the garden or in an open car park, three things matter. The housing protection class of Bemis portable units is IP65 and the operating range is -40°C to +55°C, so rain and cold are not an obstacle on their own. The place that really needs attention is the connection points:

• Raise the plug-and-socket joint off the ground; water must not collect at the contact point.
• Do not run the cable while it is still wound on a reel; a coiled cable cannot shed its heat.
• If it crosses a route used by vehicles, use a cable ramp instead of running it under the wheels.
• Do not leave the connector on the ground when charging is over; water and dust go straight into the contacts.

In short

• Measure the distance along the path the cable will follow and choose one step longer.
• Household extension leads and cable reels are not suitable for this job.
• If an extension is needed, the industrial CEE extension goes on the socket side, not on the car side.
• If the run is long, drop the current one step; the Pro Mobile 2 has six steps.
• The socket type decides the unit: a household socket means Mini Mobile, a single-phase industrial socket means Mono Mobile, a three-phase industrial socket means Pro Mobile 2.