I set off yesterday on a 120-mile M4 journey in the Range Rover, with about 50 miles of fuel left in the tank. The sat-nav, as is its habit, soon sent me a message that I didn’t have enough fuel to complete the journey, and offered to redirect me to the nearest filling station. 

My reflex was to bat this offer away, knowing I’d find a filling station in the next few miles. But at the same time it occurred to me this was the very situation to that faced by drivers of current electric cars: the trip stretches ahead but they lack the range. But why, exactly, was I completely confident about facing the Range Rover journey when I know I’d have found it much more of a challenge in a Nissan Leaf or Renault Zoe?

The answers are obvious, you may think. Electric cars have shorter ranges. On a 120-mile trip you’d need to stop at least once for a 20-30-minute fast charge, and that’s if you start with the battery 'full'. But I’ve already investigated the fast-charging arrangements on London’s westerly motorway, and found it a straightforward, rather pleasant procedure. Not perfect if you’re in a hurry, but no disaster.

So what was the nub of the problem? I kept thinking back to an early return trip to Oxford in a Nissan Leaf – at the end of which we very nearly ran out of charge. I can’t remember the exact words, but the machine started declaiming loudly that unless we stopped and pulled over, it would simply become immobile in the street.

Which was, I decided, the root of the problem. It’s acceptable to have a machine with a short range provided you have a means of getting it going when it conks, as you do with a petrol car with a gallon of fuel in your boot. Or in the hands of the RAC man. But no cranking or push starting will currently revive your electric car. It becomes a monument at the roadside.

Not any more, however. This week I heard about a new portable charging station called an EV Rescue. In effect it’s a big, smart battery that rolls on wheels like an airport suitcase and is made by a firm recently bought by Chargemaster, the UK’s biggest maker of EV charging stations.

It is meant for big fleet owners or breakdown organisations. In fact, the RAC is just beginning service trials with it. If your electric car conks (and you’re a member of the RAC) a nice man will plug this thing in and give you approximately a mile of charge for every minute. Special electronics plot the distance to your nearest dealer or charging point: a five-minute 'tickle' may be all that’s needed to get you back on the road. 

Now all we need is for these things to become miniaturised, and be portable in a boot like a gallon of gas, and for the stranded electric car owner, Bob will become your uncle.