As sales of electric cars continue to soar, so do the expectations of the people buying them. It wasn’t long ago that EVs were seen as second cars that were handy for short local hops but little more. Now owners are becoming more ambitious and are expecting to travel further afield for longer – and, in many cases, that means the possibility of hitching their battery-powered machine to a caravan or trailer. So are the latest generation of electric and hybrid vehicles up to the task? Here’s our in-depth guide with all the answers.
Why can't some electric and hybrid cars tow?
With their torquey and powerful electric motors, you’d expect EVs and hybrids to make the perfect towing partners, able to pull heavy loads with far less effort than traditional internal-combustion models. Yet dig deep into the specifications of many of these machines and you’ll discover that very few of them are capable of being hitched up to a caravan or a trailer. It’s not that you're unable physically to attach a tow bar. It’s simply that the vast majority haven’t been granted type approval.
Why not? Well, there are a number of reasons, from specific EV technology to range concerns, but perhaps the greatest stumbling block from an engineering point of view is mass. Battery packs are heavy, meaning many EVs tend to weigh a lot more than a similar sized petrol or diesel machine. (A petrol Volvo XC40 weighs at least 1655kg, whereas the electric version tips the scales at 2188kg, a 533kg difference.) Start adding extra mass to the already hefty kerb weight and you’re in danger of over-stressing already hard-working components such as the brakes and transmission. Even on the lighter hybrids (around 1800kg or so), the combined weight of car and caravan could be up to three tonnes, which would require substantial mechanical strengthening.
In a similar vein, the complex regenerative braking system is also a limiting factor. When slowing down, the electric motor in an EV or hybrid acts as a generator, pouring otherwise lost energy back into the battery. A by-product of this process is a useful ‘engine braking’ effect similar to that in internal-combustion machines. It's tuned specifically for the car’s kerb weight so there’s a risk the system could be overloaded with the extra kinetic energy created by a heavy trailer, particularly on steep descents. Of course, many EVs allow you to disengage the regenerative braking, but while this might save the motor, it would put immense strain on the friction braking system.
This is even true of braked trailers, which have a fairly simple mechanical overrun drum braking system. It’s triggered by the force of the trailer or caravan pressing on a mechanism in the tow bar as the tow car slows. However, it only works when relatively high braking loads are sensed, so for most of the time, it’s the tow car’s brakes that are doing the lion’s share of the work.