Speak EV - Electric Car Forums banner

1 - 20 of 77 Posts

·
Registered
Joined
·
3,763 Posts
Discussion Starter #1
Anyone have any theories as to why, as BEVs move into the mainstream, why they cannot be "plated" by the OEM for towing lightweight unbraked trailers

That's about 500kg.

Doesn't need to be suitable for large caravans, boats, gliders, vehicle transporters.

Would make getting rid of the ICE easier for a bunch of folk.

For the life of me, can't see that 500kg would overwhelm BEV brakes, regen etc.
 

·
Registered
Joined
·
16,846 Posts
Probably a cost saving measure for low volume production.

Tesla Model X, Y and 3 are homologated to tow.

Also the iPace.
 

·
Registered
Joined
·
3,763 Posts
Discussion Starter #4
I don't really see Zoe, Leaf, Hyundai BEVs, MG ZE as low volume specialty vehicles.

Cost saving = pure "cant be bothered" signalling.

It suggests that these mainstream BEVs are some kind of weird impaired mobililty vehicle
 

·
Registered
Joined
·
704 Posts
Can’t see an obvious reason but maybe the chassis design of smaller EVs doesn’t lend itself to attaching a towbar and accepting the load at that point.
 

·
Registered
2017 Golf GTE
Joined
·
1,922 Posts
Can’t see an obvious reason but maybe the chassis design of smaller EVs doesn’t lend itself to attaching a towbar and accepting the load at that point.
I can't see how it's any more difficult structurally than on a small ICE.

I reckon that everyone is just being cautious about overstressing a relatively low powered new drivetrain. I'd be surprised if they have not tried towing with the older designs e.g. Leaf and Zoe. Maybe something broke. Maybe they were put off by the dramatically reduced range.

Worth noting that my Golf GTE is plated for a 1500kg braked trailer. That covers a decent small caravan like my Bailey Ranger 460/2. It is also equal to the towing capacity of a PHEV Outlander! The chassis is just the ICE version modified, of course. Although the drivetrain is seriously complicated.
 

·
Registered
Joined
·
16,846 Posts
I don't really see Zoe, Leaf, Hyundai BEVs, MG ZE as low volume specialty vehicles.
To manufacturers they are, especially at the early stages when they didn’t know how many they’d sell.

Anything under 100,000 per year is low volume.
 

·
Registered
Joined
·
3,763 Posts
Discussion Starter #8
To manufacturers they are, especially at the early stages when they didn’t know how many they’d sell.

Anything under 100,000 per year is low volume.
Take Golf range, petrol about 1500kg, diesel about 1600kg, GTE 1500kg, BEV zero. Same chassis rear end.

Ionique similar story.

Not everyone who tows wants a Tesla!
 

·
Registered
2017 Golf GTE
Joined
·
1,922 Posts
Take Golf range, petrol about 1500kg, diesel about 1600kg, GTE 1500kg, BEV zero. Same chassis rear end.

Ionique similar story.

Not everyone who tows wants a Tesla!
Not everyone who tows can afford a Tesla!
 

·
Registered
Joined
·
4,094 Posts
The LEAF is capable physically of towing as this autonomous version at the factory shows.



The generally accepted story with the LEAF24 was the significant range reduction on an already short range vehicle.
 

·
Registered
Joined
·
16,846 Posts
Take Golf range, petrol about 1500kg, diesel about 1600kg, GTE 1500kg, BEV zero. Same chassis rear end.

Ionique similar story.

Not everyone who tows wants a Tesla!
Nothing to do with that. These are all examples of low rate production cars that require re-certification.

The OEMs left it off as a cost saving measure or because they didn’t think people would care to tow with a low range BEV.
 

·
Registered
Joined
·
4,094 Posts
To manufacturers they are, especially at the early stages when they didn’t know how many they’d sell.

Anything under 100,000 per year is low volume.
The MG ZS is a bad example as the petrol version is rated for 500kg. That the manufacturers opt not to tick a few boxes (there's no testing to pass) and pay the fee to claim towing on the EV must be for another reason.
 

·
Registered
MG EZS 2020
Joined
·
4,175 Posts
Anyone have any theories as to why, as BEVs move into the mainstream, why they cannot be "plated" by the OEM for towing lightweight unbraked trailers

That's about 500kg.

Doesn't need to be suitable for large caravans, boats, gliders, vehicle transporters.

Would make getting rid of the ICE easier for a bunch of folk.

For the life of me, can't see that 500kg would overwhelm BEV brakes, regen etc.
There is really no reason that most of them couldn't be used to tow, apart from what it will do to the range. The MG EZS is basically the same car as the MG ZS ICE and that can tow. I image the new Corsa/Peugeot 208 will be able to tow, but I'll lay odds the EV version will not be able to.

One thing that may explain this is the loss of range whilst towing. How many manufacturers are going to put in their advertising - Summer 163 miles Winter 140 miles Towing 80 miles?
 

·
Registered
Joined
·
333 Posts
There is a market though. In my village in normal times there are plenty of dinghies being towed a few miles to the foreshore or horseboxes the other direction to a local gymkhana, to different grazings or to avoid too much road work. Range is not that important in those cases.
 

·
Registered
MG EZS 2020
Joined
·
4,175 Posts
The MG 5 estate is reputedly able to tow.
 

·
Registered
Joined
·
603 Posts
I think I found your towing problem...

Suppose your battery is 350v, 35kv synchronous motor with 0.01ohm phase resistance, 700mm diameter tire, 6.66:1 motor:wheel gear ratio, 0.34 drag coefficient and 2m^2 frontal area, 5000lbs vehicle.

Now suppose you're moving to San Francisco California to a street with a 31.5% slope and you want enough torque to climb at 30mph with a fully loaded moving trailer that weighs in total 4400lbs...

To go 30mph up the hill without the trailer your motor generates 16.9 kilowatts of heat and 90.6 kilowatts of mechanical power which is 1301 amps through the phase windings. Once you factor in the trailer, that heating in the motor jumps to 59.1 kilowatts of heat and 169.5 kilowatts of mechanical power which is 2432 amps through the phase windings.

59.1 kilowatts of heating might just be enough to burn out the enamel on the phase windings permanently destroying the motor. & that's just factoring 30mph constant speed not the additional torque required for decent acceleration.

130161
 

·
Registered
Joined
·
4,094 Posts
Interesting theory. Certainly the motors are power and torque limited by the controllers to prevent that, meaning that the performance would be woeful in say a LEAF24 with max 80kW. The real issue is the fixed gearing - your ICE may not manage that in top but you change down to a lower gear. Then the maximum power is available and you are able to climb that hill, albeit slowly. An EV may move away from its peak efficiency but it is within its rated power and liquid cooled motors should have no issues.
Dala in Finland is currently exploring pushing the boundaries of the LEAF24's motor to release more power but has published these charts where you can see the broad spread of power available at all speeds.


In Europe even low powered cars are rated for towing (admittedly small) trailers. For example, the Dacia Sandero with 54 BHP (about 40kW so half the LEAF24's mighty 80kW) can tow 580kg. You can be sure that somewhere in Romania as you read this a local will be pulling twice that amount up the side of a mountain commenting that his previous Bullock did this no problem before inconveniently dropping dead.
 

·
Registered
2017 Golf GTE
Joined
·
1,922 Posts
I think that you've answered the question guys!

The GTE electric motor drives through the 6 speed DSG gearbox unlike almost every BEV.
So it can change down to multiply available torque just like you do when towing with a small ICE.

My own original tow car was a manual 1.6 deisel Ford Focus. And you had to drive it using the lower gears where necessary. Fuel consumption was 30 mpg towing and 50 mpg light. So a dramatic reduction in range too!

So solution would be a gearbox in the BEV power train. Low ratio transfer box anyone?
 

·
Registered
Joined
·
16,846 Posts
I think I found your towing problem...

Suppose your battery is 350v, 35kv synchronous motor with 0.01ohm phase resistance, 700mm diameter tire, 6.66:1 motor:wheel gear ratio, 0.34 drag coefficient and 2m^2 frontal area, 5000lbs vehicle.

Now suppose you're moving to San Francisco California to a street with a 31.5% slope and you want enough torque to climb at 30mph with a fully loaded moving trailer that weighs in total 4400lbs...

To go 30mph up the hill without the trailer your motor generates 16.9 kilowatts of heat and 90.6 kilowatts of mechanical power which is 1301 amps through the phase windings. Once you factor in the trailer, that heating in the motor jumps to 59.1 kilowatts of heat and 169.5 kilowatts of mechanical power which is 2432 amps through the phase windings.

59.1 kilowatts of heating might just be enough to burn out the enamel on the phase windings permanently destroying the motor. & that's just factoring 30mph constant speed not the additional torque required for decent acceleration.

View attachment 130161
Although this is clearly not the case in the real world.

Motors have cooling circuits.
 
1 - 20 of 77 Posts
Top