How to drive an EV a long distance

A couple of years ago, What Car? set a world record for the most countries visited in 24 hours in an electric car (EV), starting in the Netherlands and arriving in Serbia 14 countries (and many cans of Red Bull) later. It’s an accomplishment we’re very proud of, and one that we were convinced would be hard to top, until we heard about the exploits of an American chap called Wayne Gerdes.

You see, in the same year we set our record, Gerdes (below) broke one for crossing the United States with the least amount of time spent charging, being plugged in for less than two and a half hours en route from Los Angeles to New York. Before him, the total charging time required to cover that 2834-mile journey was well over seven hours.

What was Gerdes’ secret, you ask? Well, when he stopped to recharge, he never allowed his car’s battery to exceed 50% of its capacity, resulting in a staggering 18 stops along the way. But while this ‘little and often’ approach might seem unconventional, it’s rooted in an understanding of the way an EV's charging speed varies during a single session.

Now, it’s worth pointing out that the maximum charging speed differs for each make and model of car, but it’s fair to say most batteries exhibit similar charging characteristics. Initially, an EV with a low battery level charges slowly, but then it accelerates up to its maximum rate and typically stays there until the battery is at around 50%, at which point the charging speed tapers off again.

To illustrate, consider pouring a pint of Guinness. You can really go for it for a while, but as the glass gets fuller, the pour gradually has to slow down. By the end, the last few millilitres trickle in. Topping up a battery is very similar, because the electrons coming in have to work harder to find space.

While many EV owners are familiar with this phenomenon, Gerdes capitalised on it by stopping each charge before he fell out of the battery’s sweet spot, banking on the fact that he could get another quick top-up at his next stop. This gave us an idea: on a real-world, long-distance road trip, could Gerdes’ unconventional 50% charging strategy outpace the more typical one of waiting for the state of charge to hit 80%? Could we have indeed gone even farther during our European EV road trip?

To find out, we planned a 550-mile ‘race’ that would, in effect, take us on a lap of England, starting at Beaconsfield services, travelling up to Cumbria, across to North Yorkshire and then back down to Beaconsfield. And to keep the test fair, we would use two identical cars, with their Eco drive modes selected, regenerative braking settings set to off (due to our route being predominantly motorway-based), air-con set to 21deg C and cruise control set to the national speed limit.

The cars

For the past few months, I’ve been running a Mercedes EQE as my company car. If you’re unfamiliar with electric Mercedes models, the ‘EQ’ bit of its name means it’s an EV, while the last ‘E’ refers to its size. In other words, the EQE is a Mercedes E-Class-sized EV – or, if you prefer, a smaller, less expensive alternative to the S-Class-sized EQS.

The EQE isn’t without its faults. The rival BMW i5, for example, handles better and has a plusher interior, while cheaper models such as the Kia EV6 and Hyundai Ioniq 5 offer superior passenger space. But one area in which the EQE excels is range. And as a high-mileage driver, range is perhaps the single most important factor for me when considering an EV.

Now, that might sound like an overstatement, but unlike most of my colleagues, whose families reside in the south of England, my relatives are in Scotland; door to door, it ’s 313 miles to my parents’ house, for example. It’s a journey I undertake regularly, and it ’s relatively straightforward in a modern petrol or diesel car (I’ve completed the trip in one go in everything from an Alpine A110 to a Volkswagen Up). However, in EVs, I’ve usually suffered from some range anxiety.

Not so in the EQE. In our most recent summer range test – which involved driving the latest electric models from fully charged to completely empty at our private test track – an EQE 300 AMG Line Premium set a new What Car? record by covering 329 miles before running out of juice (just 9.7% down on its official range of 365 miles). Moreover, the Sport Edition version I have, with its smaller, 19in wheels, has an even longer official range of 380 miles, making it the ideal choice for this test.

Beaconsfield to Lancaster

We acknowledge that, typically, most EV owners would begin a long-distance journey with their battery at 100%, having topped up using a home charger. However, in the interest of getting our test under way without delay, What Car?'s Head of Video, Doug Revolta, and I arranged to meet at Beaconsfield services with only 5% remaining in our batteries.

Doug would wait until his EQE reached an 80% state of charge before setting off, while I could begin my journey once my car got to 50%. However, I would need to stop for another top-up somewhere near Birmingham, whereas Doug could aim for Lancaster services, 225 miles away.

Arriving at Beaconsfield on a misty April morning, our spirits were high, but the sight of multiple vehicles queuing for the fastest, 350kW Ionity chargers was somewhat disheartening. As was the realisation that, upon finally plugging in both cars simultaneously, the machines were delivering a maximum of only 80kW – well down on the EQE’s limit of 170kW. Ionity’s website clarifies that “if lots of vehicles are charging at once, you might find that the maximum power per charger is throttled back to keep the site within grid limits”. Not ideal.

By the time my car’s battery had reached 50%, 34 minutes had elapsed, but at least I could hit the road, whereas Doug was forced to wait for an additional 22 minutes. After doing some quick mental arithmetic, I realised that if I could locate a charger capable of delivering at least 170kW, I would probably maintain my lead over Doug as we headed up to Cumbria.

The car’s built-in navigation system directed me to stop at Gridserve Moto Hilton Park on the M6, where all six 350kW fast chargers were available. Doug and I had agreed beforehand to rely solely on our cars’ built-in sat-nav systems, foregoing phone apps such as Google Maps or Waze. This decision was driven by the cars’ pre-conditioning feature, which only activates when navigating to a charger plugged into the native system.

If you’re unfamiliar with pre-conditioning, the concept is akin to warming up before a run. Just as muscles perform better when properly warmed up, batteries function optimally at certain temperatures. Pre-conditioning the battery primes it to charge as quickly as possible by bringing it to its ideal temperature.

With my battery nicely warmed up, the charger delivered an average speed of 124.87kW/hour – considerably faster than the Ionity chargers back at Beaconsfield, although still some way short of the desired 170kW. Nonetheless, in just under 20 minutes, I was back on the road – and a brief call to Doug confirmed that I was still in the lead.

Lancaster to Grantham

With the cruise control set to 70mph and the traffic on the M6 remarkably light, I reached Lancaster services in just over two hours with 18% remaining. After plugging in to the nearest available charger, I dashed inside to grab a cooked lunch for myself and cameraman Jonty – a decision I quickly regretted. Monitoring the progress through my MercedesMe app, I noticed that after only 10 minutes of charging, I was closing in on 50% and the fast food I had ordered wasn’t coming very fast…

Returning to the car just as it hit 50% charge, I saw Doug already plugged in beside me. With no time for pleasantries, I resumed my position behind the wheel and headed towards North Yorkshire via Carlisle. Feeling confident that I had the situation under control, I was taken aback when Doug called to inform me that his charge from 4-80% had taken only 37 minutes – an average of 121.92kW/hour, just 2.59kW/hour slower than my charging session.

That meant I hadn’t extended my lead by any great margin; Doug was still just 20 to 25 minutes behind me on the road. It was also around this time that I noticed my range was dropping quicker than I expected on the climb over the Pennines. So, instead of pushing on to a set of Gridserve chargers at Ferrybridge services in West Yorkshire, I elected to stop early at Moto Leeming, just past Scotch Corner.

Frustratingly, the chargers at Moto Leeming are situated five minutes off the motorway in a rather isolated car park adjacent to a McDonald’s restaurant – a detour that feels more substantial when you’re engaged in a contest with your colleague. And to make matters worse, the first charger I tried was broken. As were the second, third and fourth, while the two remaining (working) chargers were occupied.

Aware that Doug was closing in on me, I hastily contacted Gridserve, only to be put on hold as the customer service team tried to reboot one of the machines – a process that took well over 10 minutes. During this time, one of the occupied chargers became available. Once plugged in, the charging speed peaked at 130kW and held steady for just over 18 minutes. That wasn’t bad, but factoring in the delays, I found myself stationary for 36 minutes – giving Doug plenty of time to overtake me and establish an insurmountable lead.

Grantham to Beaconsfield

After another phone call, we realised that Doug had surged ahead to such an extent that, barring any major setbacks for him at Gridserve Grantham, there was no chance of me catching up and retaking the lead by the time we reached our end point at Beaconsfield services. Therefore, we adjusted our strategy accordingly.

Instead of topping up our cars at Grantham to the minimum level required to return to Beaconsfield, as initially planned, Doug opted to charge once more to 80% and wait for me to arrive, while I stuck to 50%. This adjustment allowed us to gather even more data for analysis upon our return to Beaconsfield.

As it transpired, Doug’s final charging session proved to be the quickest of his entire journey, delivering a total of 69kWh in just 31 minutes, thanks to an average speed of 133.18kW/hour – slightly faster than my average of 125.55kW/hour.

With Doug’s victory in the bag, we elected to leave Grantham together. Doug ceremoniously led the way back to Beaconsfield services, marking the end of a rather exhausting yet, we like to believe, productive day.

Lessons learned

Across my five charges, I achieved an average charging speed of 113.6kW/hour, compared with Doug ’s 108.7kW/hour for his three stops – a difference of 4.9kW/hour. This translates to a combined charging time of 1hr 42min for me and 2hr 5min for Doug – a significant 23-minute saving by sticking to the 50% charging strategy.

Therefore, Gerdes is technically correct. In an ideal world, where queues are nonexistent and the chargers are all operational and deliver electricity at the maximum rates cars can accept, making shorter, more frequent stops would indeed be superior.

However, in the real world of our test, the advantage gleaned from this strategy was cancelled out by the challenges of the UK’s imperfect public charging network. Stopping for longer and replenishing your car’s battery to 80% is more practical, because you’ll be able to go farther before you need to gamble again with the charging infrastructure. As Doug pointed out upon our return to Beaconsfield services: “Your strategy might have been faster in theory, but I'm the one who looks and feel a lot less stressed.”

Despite the outcome, there are lessons to be learnt from our experience. It was evident that Doug lost considerable time right from the outset – remaining connected to a charger that was delivering just 41.7% of the EQE’s maximum charging rate. So, if you encounter a similar situation and possess sufficient range to reach an alternative charging location, it might be worth simply unplugging and moving on, in the hope that the next one is better.

Our journey also underscored the benefits of having a long range at your disposal. Despite adopting a brisk pace (staying at the national speed limit where possible), our EQEs achieved efficiency figures that would have yielded a real-world range of just under 300 miles if we’d departed with full batteries. With this sort of capability, long journeys in an EV are much less stressful. That’s handy if you and your folks live at opposite ends of the country.

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