Planning a long drive through several countries

Range is a statement about the car. The state of charge you arrive with at the next charge point is a statement about the leg — and only the leg can be planned. Set every leg so that you arrive with a predetermined remainder and you carry the same margin at every point of the trip, whatever the weather, the pace and the traffic do.

That remainder is not a figure that belongs in print but a rule: it has to be enough to reach the next alternative if the planned point is out. The number then follows by itself — and it is a different number in Sweden than in the Ruhr, because the spacing of the alternatives is different.

The second quantity is the state of charge you leave a stop with. The charging curve says the topmost percentages go in slowest; the reserve rule says how much you need at the far end. The leg is the gap between the two — and it is shorter than any range figure suggests, because neither the top nor the bottom of the pack is being used.

Charging infrastructure follows traffic, and traffic follows a handful of axes. Along the major European through-routes the charge parks stand close together; twenty kilometres off them it thins out, and in a valley or on a peninsula the next alternative can be a very long way away. So the question is never how well a country is equipped, but how well the corridor you are driving is.

A detour to a charge point always costs twice: out and back, plus the time for both. Ten kilometres off-route is twenty kilometres of energy and a quarter of an hour you would have to win back at the stop. Sites directly on the line of travel are therefore almost always the better choice, even when another one looks more powerful on the map.

And a corridor does not end at a border; it ends where the through-route ends. A journey that leaves a motorway for a secondary road changes its charging profile at the same moment — and that moment usually coincides with entering a region, not with entering a country.

A single charge point is not a plan but a hope. It can be occupied, faulty or fenced off by roadworks, and none of those three announces itself in advance. A site with several points is therefore worth a detour that a more powerful single point is not.

Occupancy has patterns, and they are predictable: the start of a holiday period, a Sunday evening, the tail of a long weekend, bad weather that puts everyone on the road at once. Travelling inside one of those windows means planning a bigger reserve and earlier stops — not because the car can do less, but because the queue has become part of the leg.

Handling it is unspectacular: for every leg there is one point in the plan and a second one in your head, and the second sits nearer than the first. If the first is out, you drive to the second and still hold the reserve you had allotted for reaching the first.

On a stretch where very high speeds are permitted, a driver faces a genuine trade-off. Going faster shortens driving time and lengthens charging time, because consumption rises with the cube of speed. Whether the net result is quicker depends on how fast the car takes the extra energy back in.

The trade-off resolves differently for a car with a flat, high charging curve than for one whose power collapses early. With the first, speed costs little because the energy comes back quickly; with the second, every extra kilowatt-hour is paid for with disproportionate standing time. That is the real reason two cars with identical range take different lengths of time over the same route.

In countries where the limit applies throughout, the question does not arise — the pace is given and the planning simpler. Which limit applies, and where it differs, is published by that country's traffic authority; it changes, and it is the one part of this calculation you have to look up rather than work out.

In the Alps the car is driven onto a train at several places and carried through the mountain; over water a ferry does the same job. In both cases you hand over control of the vehicle for a while, and in both cases the operator's rules apply rather than the road's.

For vehicles with high-voltage batteries, operators sometimes set their own requirements: where the car is stowed, what state of charge it may arrive in, whether people may remain inside, and how an incident is to be reported. Nowhere does charging happen during the crossing. These requirements differ by operator, they change, and they live in the conditions of carriage — read them when you book, not at the ramp.

Three things follow for planning. Loading is time in which you are neither driving nor charging — it lengthens the leg without shortening it. The queue in front of it is often in the open and costs cabin heating in winter. And the charge point on the far side belongs in the plan, because the arrival side of a tunnel or a port is rarely where you want to improvise.

Technically almost nothing: the plug is the same, the voltage is the same, the cars are the same. What changes is your contractual position — which networks your provider covers — and the density of points. Both can be settled before departure, and afterwards only endured.

In practice three small things change that add up to more than they sound. The language on the display, because not every unit switches. The operator's phone number, which abroad may not be reachable free of charge. And the last site before a border, which is reliably busier than the first one after it, because many drivers prefer to charge inside the network they know.

From which follows an unspectacular recommendation: plan the leg across the border, not up to it. The first site in the new country is almost always the quieter one, and the session there is the test of whether your preparation held — taken with a full reserve rather than an empty one.

The plan formed in spring on an empty commute does not hold for a holiday run. Four people, luggage and a roof box change both mass and frontal area, and at cruising speed frontal area matters more than weight. Use your usual consumption figure and the legs come out too long — as you will discover on the second one.

The clean approach is to make the first leg deliberately short and read the actual consumption before planning the rest of the day. An hour on the road fully loaded says more about the trip than any advance calculation — and it costs nothing, because you were going to drive it anyway.

With a trailer this stops being a correction and becomes a different journey: different leg lengths, a different selection of sites, different stops. That carries its own set of rules, which do not fit in here.

A good travel plan is not made of clock times but of decision points. At every stop you decide afresh how far the next leg goes — using the last hour's consumption rather than a figure from spring, and the weather now rather than yesterday's.

That is the genuine difference from driving a combustion car, and it is smaller than it looks from outside. It is not that the range is shorter; it is that the feedback is immediate — you see the consequence of a decision within the same leg.