5 ms·

This seems like an interesting solution to the "what to do if my battery runs out in the middle of nowhere" problem. Normally, you'd either have to have to cal

by elihu 5y ago

This seems like an interesting solution to the "what to do if my battery runs out in the middle of nowhere" problem. Normally, you'd either have to have to call a tow truck or have someone with a generator come along and recharge. However, towing for awhile (probably at much less than 70 mph for safety reasons) to recharge the battery enough to get to the next town is something that could presumably be done by just about any passing car if you have a tow strap (which could be stored in the EV for such an occasion).

bin_bash 5y ago
On the Long Way Up they did just this to recharge their Rivians
- lttlrck 5y ago
  That is a fantastic show. Rivian and Harley (electric bikes) did great.
kllrnohj 5y ago
Only if any of those passing cars are gas-powered. If the passing cars are themselves also EVs, then there's both more obvious forms of energy transfer, but also you'll be taking that much range (and more) from the EV doing the towing.
- r00fus 5y ago
  Cost asymmetry - if I had the spare battery capacity (assuming I'm only doing local drives) I'd happily donate it to someone stranded. It's like giving a fiver to fill up emergency gas if they're broke at a gas station.
- elihu 5y ago
  Transferring energy from one car to the other isn't quite that straightforward, even though it's something that sounds like it ought to be easy. (The simplest thing would be jumper cables, but there's not usually any easily-accessible high voltage terminals, and the batteries might be different voltages anyways. And you'd want to limit curren, and so on....) Maybe if the new Ford F150's 220-volt outlet becomes a common feature, then charging from one car to anther will be easier (though very slow). I think the main towing advantage a typical ICE car would have over an EV with extra battery capacity is the ability to shift into 1st or 2nd gear. It's not really an intrinsic property of EVs that they can't have transmissions, but so far the major manufacturers have decided it's not worth it. (The Taycan is a notable exception.)
saalweachter 5y ago
Given the mileage of towing a vehicle with its brakes on, I can't imagine it wouldn't be more efficient to just tow the stranded vehicle to a charger.
- elihu 5y ago
  When you're stranded, energy efficiency isn't the top concern: any solution that works could be an acceptable one. And it's probably a lot easier to tow a car on a long straight road for awhile then cut them loose than it is to tow a car through intersections and into parking lots to find a charger.
  - SV_BubbleTime 5y ago
    I work in automotive, I’ve seen some amazingly bad towing examples. Sounds like a decent solution to get two vehicles stranded. I would think unless the tide is coming in, getting a generator and hanging out for awhile would be a safer for everyone solution.
    - throwaway0a5e 5y ago
      >I’ve seen some amazingly bad towing examples Are we talking genuinely dumb things like forklift loaded facing forwards on a small utility trailer or the typical online pearl clutching when someone is 100lb over their tire rating?
      - SV_BubbleTime 5y ago
        The former :) Tongue weight, what is it and how does it work? I guess we’ll never know!
quickthrower2 5y ago
It probably means you need to get someone to tow you halfway to a town. But there isn't that much advantage over towing you all the way to a power outlet. And once you are asking strangers for help, just toe you to a residence that is happy to power you up.
- jsight 5y ago
  The residence won't charge anywhere near as quickly as this, though.
  - ryanmarsh 5y ago
    The Tesla charger at my residence charges the car at ~30mph
    - anonporridge 5y ago
      I love this measure of charging speed. I'm wondering now why I haven't ever seen it used before.
      - fiddlerwoaroof 5y ago
        This is pretty standard: the Tesla charging screen shows this while charging.
      - watt 5y ago
        It is getting more popular, also because vehicles charging at same energy input (say, 100 kW) can show larger kmh value (or mh) depending on how efficient the car is: the more efficient car can go further on the same energy input.
        quickthrower2 5y ago
        I imagine this might incentivize cars optimized for the maximum efficient speed rather than top speed, (so they can report the most miles per hour when charging).
lostapathy 5y ago
It’s actually really dangerous and generally illegal to tow a vehicle with a simple, easily stored strap.
- throwaway0a5e 5y ago
  It's more dangerous than sitting in an air conditioned office and posting on HN but if you're not trying to keep up with stop and go traffic it's not substantially worse than flat towing. You have to drive like a responsible adult and trust your buddy to do the same but that kind of goes without saying for any situation where you're moving double or more the weight you usually do.
  - lostapathy 5y ago
    This is really terrible advice. It's super dangerous, especially at highway speeds (i.e., fast enough to charge a tesla). Granted, leaning on the brake regen makes pulling a tesla a little less dangerous than pulling a gas car around at speed. There's a reason this is illegal most places. It's also, generally, pretty hard on both vehicles to tow on a non-rigid connection because there's a lot of shock transmitted between vehicles whether the rope goes slack.
    - throwaway0a5e 5y ago
      You don't need to go 70mph to regen a Tesla. They went fast in the article in order to get the wattage up to an impressive article-worthy number. 20mph would work but more slowly. There shouldn't be much if any shock loading because the towed vehicle will be on the brakes the whole time. Obviously some good judgement is advised. Roads with hairpin turns or the shoulder of a major urban interstate is not the place for this. Obviously a tow bar would be better than a rope but nobody winds up in a situation where they need to regen tow a vehicle because of an abundance of alternative good options. I guess I was a little too generous to HN when I assumed I didn't need to include a bunch of "be reasonable about it" disclaimers in my original comment.
dahfizz 5y ago
> However, towing for awhile ... is something that could presumably be done by just about any passing car A Tesla model 3 weighs over 4000 pounds. A base model Toyota Tacoma isn't even rated to tow that weight, there's no way any passing sedan could. Now remember that for regenerative _braking_ to work, the tesla's brakes have been on! Definitely not something any passing car can handle.
- Gustomaximus 5y ago
  > A base model Toyota Tacoma isn't even rated to tow that weight Isnt this rating more about supporting and breaking force for the combined vehicle and load weight. My understanding in this case tow means 'pull the vehicle' vs carry the front weight. So I think even a smaller car would be fine to pull a Tesla.
  - dahfizz 5y ago
    Being able to safely break is part of the towing test, as well as being able to haul the load up hill at highway speed. The point is that an average sedan absolutely does not have the power to tow 4,000 pounds, let alone 4,000 pounds with it's breaks on.
  - throwaway0a5e 5y ago
    >Isnt this rating more about supporting and breaking force for the combined vehicle and load weight. There are braking requirements in the test but the bottleneck is almost always (i.e. I want to say always but I don't put it past Dodge to show up with a 700hp vehicle) the acceleration and minimum speed up a grade portions of the test. Given the weight that can be accelerated and pulled up a grade per the test requirements basically every vehicle winds up passing the braking portion with room to spare. But if you get all your vehicle performance advice on Reddit and HN I can see why you'd think brakes are always the bottleneck.
- matt-attack 5y ago
  The weight of the Tesla is moot. The majority of the load experienced by the pulling vehicle is in the incredible drag of the Tesla’s wheels. They’re extremely difficult to spin and this for pace far exceeds any others that would normally be encountered when pulling a traditional load.

by elihu 5y ago

bin_bash 5y ago

On the Long Way Up they did just this to recharge their Rivians

lttlrck 5y ago
That is a fantastic show. Rivian and Harley (electric bikes) did great.

kllrnohj 5y ago

Only if any of those passing cars are gas-powered. If the passing cars are themselves also EVs, then there's both more obvious forms of energy transfer, but also you'll be taking that much range (and more) from the EV doing the towing.

r00fus 5y ago
Cost asymmetry - if I had the spare battery capacity (assuming I'm only doing local drives) I'd happily donate it to someone stranded. It's like giving a fiver to fill up emergency gas if they're broke at a gas station.
elihu 5y ago
Transferring energy from one car to the other isn't quite that straightforward, even though it's something that sounds like it ought to be easy. (The simplest thing would be jumper cables, but there's not usually any easily-accessible high voltage terminals, and the batteries might be different voltages anyways. And you'd want to limit curren, and so on....) Maybe if the new Ford F150's 220-volt outlet becomes a common feature, then charging from one car to anther will be easier (though very slow). I think the main towing advantage a typical ICE car would have over an EV with extra battery capacity is the ability to shift into 1st or 2nd gear. It's not really an intrinsic property of EVs that they can't have transmissions, but so far the major manufacturers have decided it's not worth it. (The Taycan is a notable exception.)

saalweachter 5y ago

Given the mileage of towing a vehicle with its brakes on, I can't imagine it wouldn't be more efficient to just tow the stranded vehicle to a charger.

elihu 5y ago
When you're stranded, energy efficiency isn't the top concern: any solution that works could be an acceptable one. And it's probably a lot easier to tow a car on a long straight road for awhile then cut them loose than it is to tow a car through intersections and into parking lots to find a charger.
- SV_BubbleTime 5y ago
  I work in automotive, I’ve seen some amazingly bad towing examples. Sounds like a decent solution to get two vehicles stranded. I would think unless the tide is coming in, getting a generator and hanging out for awhile would be a safer for everyone solution.
  - throwaway0a5e 5y ago
    >I’ve seen some amazingly bad towing examples Are we talking genuinely dumb things like forklift loaded facing forwards on a small utility trailer or the typical online pearl clutching when someone is 100lb over their tire rating?
    - SV_BubbleTime 5y ago
      The former :) Tongue weight, what is it and how does it work? I guess we’ll never know!

quickthrower2 5y ago

It probably means you need to get someone to tow you halfway to a town. But there isn't that much advantage over towing you all the way to a power outlet. And once you are asking strangers for help, just toe you to a residence that is happy to power you up.

jsight 5y ago
The residence won't charge anywhere near as quickly as this, though.
- ryanmarsh 5y ago
  The Tesla charger at my residence charges the car at ~30mph
  - anonporridge 5y ago
    I love this measure of charging speed. I'm wondering now why I haven't ever seen it used before.
    - fiddlerwoaroof 5y ago
      This is pretty standard: the Tesla charging screen shows this while charging.
    - watt 5y ago
      It is getting more popular, also because vehicles charging at same energy input (say, 100 kW) can show larger kmh value (or mh) depending on how efficient the car is: the more efficient car can go further on the same energy input.
      - quickthrower2 5y ago
        I imagine this might incentivize cars optimized for the maximum efficient speed rather than top speed, (so they can report the most miles per hour when charging).

lostapathy 5y ago

It’s actually really dangerous and generally illegal to tow a vehicle with a simple, easily stored strap.

throwaway0a5e 5y ago
It's more dangerous than sitting in an air conditioned office and posting on HN but if you're not trying to keep up with stop and go traffic it's not substantially worse than flat towing. You have to drive like a responsible adult and trust your buddy to do the same but that kind of goes without saying for any situation where you're moving double or more the weight you usually do.
- lostapathy 5y ago
  This is really terrible advice. It's super dangerous, especially at highway speeds (i.e., fast enough to charge a tesla). Granted, leaning on the brake regen makes pulling a tesla a little less dangerous than pulling a gas car around at speed. There's a reason this is illegal most places. It's also, generally, pretty hard on both vehicles to tow on a non-rigid connection because there's a lot of shock transmitted between vehicles whether the rope goes slack.
  - throwaway0a5e 5y ago
    You don't need to go 70mph to regen a Tesla. They went fast in the article in order to get the wattage up to an impressive article-worthy number. 20mph would work but more slowly. There shouldn't be much if any shock loading because the towed vehicle will be on the brakes the whole time. Obviously some good judgement is advised. Roads with hairpin turns or the shoulder of a major urban interstate is not the place for this. Obviously a tow bar would be better than a rope but nobody winds up in a situation where they need to regen tow a vehicle because of an abundance of alternative good options. I guess I was a little too generous to HN when I assumed I didn't need to include a bunch of "be reasonable about it" disclaimers in my original comment.

dahfizz 5y ago

> However, towing for awhile ... is something that could presumably be done by just about any passing car A Tesla model 3 weighs over 4000 pounds. A base model Toyota Tacoma isn't even rated to tow that weight, there's no way any passing sedan could. Now remember that for regenerative _braking_ to work, the tesla's brakes have been on! Definitely not something any passing car can handle.

Gustomaximus 5y ago
> A base model Toyota Tacoma isn't even rated to tow that weight Isnt this rating more about supporting and breaking force for the combined vehicle and load weight. My understanding in this case tow means 'pull the vehicle' vs carry the front weight. So I think even a smaller car would be fine to pull a Tesla.
- dahfizz 5y ago
  Being able to safely break is part of the towing test, as well as being able to haul the load up hill at highway speed. The point is that an average sedan absolutely does not have the power to tow 4,000 pounds, let alone 4,000 pounds with it's breaks on.
- throwaway0a5e 5y ago
  >Isnt this rating more about supporting and breaking force for the combined vehicle and load weight. There are braking requirements in the test but the bottleneck is almost always (i.e. I want to say always but I don't put it past Dodge to show up with a 700hp vehicle) the acceleration and minimum speed up a grade portions of the test. Given the weight that can be accelerated and pulled up a grade per the test requirements basically every vehicle winds up passing the braking portion with room to spare. But if you get all your vehicle performance advice on Reddit and HN I can see why you'd think brakes are always the bottleneck.
matt-attack 5y ago
The weight of the Tesla is moot. The majority of the load experienced by the pulling vehicle is in the incredible drag of the Tesla’s wheels. They’re extremely difficult to spin and this for pace far exceeds any others that would normally be encountered when pulling a traditional load.