I’ve just ran an electric van down to 0% battery charge so that you don’t have it.
I have to say it wasn’t a pleasant experience, and it was done entirely by accident, but it turned out to be an interesting insight into how the systems prepare you, mentally and emotionally, for your impending breakdown.
So here's what happens when your electric car battery dies, and this is how I got to the point of completely running out of electricity in an electric vehicle.
I started my 150 mile journey with the battery in my electric van charged to more than 85% and an indicated range of just over 180 miles. I won’t name the electric van I was driving, as it’s not an exercise in pointing fingers, because all EVs behave similar to this.
The trip was to cover thirty or so miles on country lanes before completing the rest of the journey on the motorways. I left late, and traffic was light, which meant I was immediately travelling at the maximum permitted speed. Using the regenerative braking and coasting modes by the time I reached the motorway the battery range and distance to my destination were still tracking at the 30 miles difference they had been at when I set out.
For the first ten or so miles on the motorway that continued, and with the van set at a cruise on 70mph I was confident that I’d make my destination and a recharge with minimal fuss.
After perhaps 15 minutes, though, the range differential began to fall. Soon the miles were falling at a gradual rate. At the halfway point there was still around 20 miles difference, but given the decline I eased back on the speed a fraction.
Electric vehicles don’t like the higher speeds of the motorways for two reasons, the constant velocity builds up heat in the battery, while also giving little to no respite that would normally come from regenerative braking.
With around 20 miles to go it became clear this was going to be quite close, the difference was just five miles. Having run out of battery, deliberately, many years ago in a very early EV to test the ultimate range of the battery I was aware that the ending would likely be abrupt, but also that that ending would be considerably after the indicated range clicked to zero.
This time, and speaking to colleagues after the fact, that wouldn’t be the case for almost all EVs nowadays. Instead you get a stage-managed decline, and a pretty swift ending, and what was about to happen scared the living daylights out of me.
The battery level hit 5% and despite being just a handful of miles from my destination, still with a zero mile difference, my indicated range disappeared from the dash display.
Not long after that, and with the battery at 3%, it went into tortoise, or limp home, mode.
Limp Mode, sometimes called Tortoise Mode, didn’t start off too badly. There was a noticeable dulling of the throttle (I’d long ago given up any form of meaningful acceleration) but it was maintaining speed. Then I reached what would turn out to be the first of many inclines.
All of a sudden the meaning of Limp Mode bit hard, I was at a crawl, my speed dropping drastically to below 45mph, not great for a motorway. But thankfully it was an exceptionally quiet one.
Reaching the top of the hill, it levelled out but the speed didn’t increase. I stayed stuck in the low forties. Then disaster. Another massive hill.
No sooner had I hit the climb, I lost all momentum. My speed fell to just 21mph. I crawled up what felt like an Everest-sized mountain, hazards flashing, and confused HGVs passing at full speed.
Relief came from the off-ramp and a red light at the junction. I coasted to a near standstill, 50 metres short of the roundabout, unsure whether I would be able to move off again.
As the light went green, I tentatively accelerated, and to my amazement was able to resume my 20mph crawl.
Taking my exist off the roundabout, the road dipped downwards. Although desperate to get to my destination, now just over a mile away, I resisted the urge to try to accelerate. I slammed the regenerative braking to its maximum and let the battery flood with recuperated energy.
The dead battery, which had now been on 0% for at least three miles, briefly jumped up to 1%, then slammed back down to 0% the moment I began to gently accelerate as the hill levelled out.
Another agonising few minutes, still travelling at my now slightly higher speed (thanks to the momentum of the hill) and I could see the lights of what I assumed would be my stop and the charging station.
As I pulled in, I scanned the area for the charger. No sign. My heart sank, but after a very slow lap of the car park, I located my salvation. A massive rapid charger, bathed in a pink glow. There was even a spare space.
I plugged in, and once the charger and van began to talk, the picture above was the result of the battery analysis. Zero percent battery. Zero kW. A completely dead battery.
How I made it there, I'll never know. But if you ever forget to charge your battery, don't worry too much, the warning signs will come thick and fast, and providing you take some immediate action, you may just be lucky, like me, and make it to a charger.
No, the chances are that your car won't stop at 0 miles, but the chances of you seeing a range of zero miles is also pretty slim. The car or van will likely manage the decline, and the range indicator will go blank. The car will continue to run, for a short while, but you'll experience a considerable slow down and loss of functions before stopping.
In the context of an EV, Limp Mode (often symbolised by a little tortoise) is when the electric vehicle attempts to salvage every remaining bit of power and also alert you that you're in a pretty desperate situation. Just remember, if you see the tortoise, slow and steady wins the race.
