As things currently stand there are indeed significant challenges charging while towing, in other words finding a rapid charger that an electrical car towing a trailer/caravan can use. However, let’s discuss a scenario where finding rapid chargers for electric cars towing is not an issue. Let’s discuss the other factors you need to consider about charging an electric car that’s going to be towing. What I want to discuss is the differences between the theory of range/charging speeds/energy consumption and real-world situations.
Table of Contents
Introduction
I’ve previously written several guide articles now on low-speed departure/destination charging and fast/rapid charging providers currently operating in the UK. Followed by an article on the fastest charging electric tow cars. I’ve also discussed other important topics which impact the range of an electric car while towing.
For instance, I’ve written about how to understand electric car efficiency figures and how factors such as speed and aerodynamic drag impact towing range. You will often read me state ‘you should expect around a 50% reduction in range when towing‘.
However, you should be aware that quoted figures from manufacturers and industry organisations on charging speeds and range are dependent on a specific set of circumstances. Furthermore, my own statement of a ‘50% reduction in range‘ is a general estimate.
Therefore, what I wanted to do with this article is discuss when charging speeds may not achieve the official figures, or when towing range may be more or less than a 50% reduction. Furthermore, to provide more context on how to prepare for a journey towing with an electric car.
Electric Car Range Reductions When Towing
When I write my articles as part of the electric tow car list I use a range figure from the EV-Database which is more realistic than WLTP figures quoted by manufacturers. I then give a 50% range figure for towing based on that EV-Database average range figure.
As I’ve previously discussed in my articles linked above, besides the weight of the trailer/caravan its aerodynamic drag is a significant part of the range reduction when towing. Travelling speed is also an important factor, there can be a big difference in range towing at 50mph compared to 60mph for instance.
So let’s discuss a theoretical example, the Skoda Enyaq iV 80 has a stated WLPT figure of between 317 and 332 miles. The EV-Database.uk gives the cars a more realistic average range rating of 260 miles. In my article on the car, I then give a 50% towing range estimate of 140 miles.
Now let’s compare that to a real-world example with the video below filmed by the CarWoW YouTube channel towing a Bailey Discovery caravan behind the Skoda Enyaq iV 80 at 60mph. Matt tows the caravan for 10 miles around a circular test track to get an efficiency reading to calculate the cars towing range.
The efficiency figure turns out to be 1.3 miles per kWh, therefore the 77kWh usable capacity of the car would provide a range of just 100 miles. Hence, obviously nowhere near 50% of the cars official WTPL range and not even close to the 50% of the much more realistic EV-Database range figure.
However, you have to remember the context, this was a test only travelling at 60mph on the motorway. Most journeys have a section of motorway driving along with sections of slower speed roads. At lower speeds there is significantly less air resistance/aerodynamic drag, hence the vehicle has a longer range.
Though the point remains, towing with an electric car on the motorway can dramatically reduce an EVs range. This is the crux of my BEV vs PHEV article when it comes to towing. If you tow less than 100 miles many current BEVs can do the job, but for more than 100 miles then a PHEV for the moment may be a necessary evil.
Calculating Range and Charging Stops When Towing
Let’s use the example again of the Skoda Enyaq iV 80 and its 100 mile (60mph) to 140 mile (mixed speed) towing range. To make this scenario simple to understand let’s say you’re going on a motorway only journey and you’re going to travel at 60mph for 200 miles. Would a single rapid charge get you to that destination?
On the face of it, the answer would appear to be yes, you travel 100 miles, you recharge then you can travel another 100 miles. But for that scenario to be true, it means two things. First, you depleted the battery to 0% when you got to the charger, and you charged to 100% to arrive at your destination with 0% charge.
Would anyone rationally plan to arrive at a charger with a 0% state of charge? Of course not, therefore the first question is what percentage of remaining charge are you comfortable with, 10%, 15%, 20%? That’s a personal preference each EV owner has to decide considering factors such as potential broken chargers/queue’s to charge/access to chargers etc.
Then there is the charging session itself, and when rapid charging there is something to important to understand. Current battery technology is pretty slow at charging (even rapid charging) from 0% to 10% rate of charge and from 80% to 100%. Hence, in many instances, the quoted rapid charging time of an EV is between a 10% and 80% state of charge.
Therefore, for this example of a 200 mile trip while theoretically its a single rapid charge stop, in reality, its a two rapid charge stop journey at least. Arriving at a rapid charger with 10% battery remaining would be the first leg of the journey at 90 miles. The car is then rapid charged to 80% giving a driving range of 70 miles to arrive at the next rapid charger with 10% state of charge remaining.
After this second rapid charging stop, you would still have 30 miles of the journey left to go. Furthermore, this is based on the presumption you are comfortable arriving at a rapid charger with 10% battery remaining which would be a very uncomfortable experience for some.
Different Rapid Charging Times/Speeds
If we continue with the example of the Skoda Enyaq iV 80 it has a rapid charging speed of 135kW. On the face of it, someone could look at that figure and go, ‘well at a suitably rated rapid charger which can provide that amount of power the 77kWh battery should be recharged in a little over half an hour‘.
However, that’s not the case, the stated rapid charging time of 10% to 80% state of charge is 33 mins. Hence, to put just 70% into the battery is going to take at least half an hour. The reason is, that 135kW rate of charge is the maximum, and charging speed is not linear, it varies.
Its also important to note, with current electric cars that the quoted 10% to 80% state of charge time is also not constant. Its effectively a best-case scenario and will only be achieved when the temperature of the battery is to borrow an astronomy term in the ‘goldilocks zone‘. In other words, the battery temperature is not too cold, its not too hot, its just right.
For example, if you take an electric car that has only travelled a few miles to a rapid charger and the battery is cold it will not achieve its official rated rapid charging time from 10% to 80% state of charge. Likewise, there is a potential for an electric car where the battery has been worked particularly hard (maybe towing) and above its ideal temperature to throttle its rapid charging speed.
The latest generation of electric cars from several manufacturers feature more advanced thermal management systems which can heat and cool the battery. You should look out for terms such as ‘battery preconditioning‘ which is when the car knows its going to a rapid charger it will try and get the temperature of the battery into the ‘goldilocks zone‘ to charge as fast as possible.
My general point is though when it comes to rapid charging speeds/time to charge don’t expect it to match the official specifications in every instance. In some situations the cars quoted charging time will closely match the quoted figure, just don’t presume that will be the case.
Conclusions On Charging, Energy Consumption & Towing
So what should you take away from my comments above? Well, based on current electric car technology when it comes to towing you need to carefully plan your journies. You need to plan the trip around the conditions/factors specific to your journey. Will you be travelling at motorway speeds for a significant part of the journey for instance etc.
We are starting to see better trip computers built into electric cars that are rated to tow that factor in the loss of range when towing. However, we are still quite a far way off electric cars providing a reliable range estimate when towing as they just don’t factor in all the variables.
As electric car technology develops and we get cars with longer ranges/faster-charging speeds the challenges associated with towing will become less and less prominent. However, for quite a few years yet towing with an electric car is going to be a significant challenge in some instances.