Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Towing a Tesla at 70 MPH replenishes battery at fast charger rates

insideevs.com

Post reply on HN
Print view View original

351–360 of 399 posts

Re: Towing a Tesla at 70 MPH replenishes battery at fast charger rates

#351

Post by throwaway0a5e »

dahfizz wrote: post #273
elihu wrote: post #120

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 a…

> 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.

All modern trucks are conservatively rated in the towing department because of the grade pulling requirement in the test all the OEMs use.

Re: Towing a Tesla at 70 MPH replenishes battery at fast charger rates

#352

Post by throwaway0a5e »

SV_BubbleTime wrote: post #264
elihu wrote: post #209

Earlier quoted context omitted.

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.

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.

>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?

Re: Towing a Tesla at 70 MPH replenishes battery at fast charger rates

#353

Post by fortyrod »

fho wrote: post #343
jgjot-singh wrote: post #338

Earlier quoted context omitted.

Perhaps the trains could partly be passenger trains, costing amusemant park rates. Then collected money could eventually pay off the cost of construction, and eventually maybe even offset the maintenance cost. If nothing else, it would certainly boast the advantage of being more fun than water storage.

Ideally have the transportees walk up the hill by themselves, summer sledding style. That way you are by some strange definition guaranteed to be net positive ;-)

I think you are on to something here. Make all elevators in hi-rises down-only and all stairwells up-only. Convert falling excess desk-jockey blubber into usable electricity while lowering rate of CV disease and generally improving fitness. Downside is probably a lot of BO that didn't exist before.

Re: Towing a Tesla at 70 MPH replenishes battery at fast charger rates

#354

Post by throwaway0a5e »

lostapathy wrote: post #213
elihu wrote: post #120

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 a…

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

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.

Re: Towing a Tesla at 70 MPH replenishes battery at fast charger rates

#356

Post by MisterTea »

adonovan wrote: post #214
shkkmo wrote: post #210

Earlier quoted context omitted.

> This is commonly called power braking, usually called up in an emergency. I've never heard it called power braking, always engine braking or j-braking. It isn't just useful in emergencies but also in steep descents with heavy loads to make sure your brakes stay cool enough to be useful. It may be obvious, but the other technique that really helps keep your brakes cool is descending more slowly.

Also known as "jake braking". It's useful if you're a dump-truck driver who thinks midtown Manhattan is too quiet.

A real "Jake brake" (Invented by Clessie Cummins) slows a truck down by turning the engine into an air compressor. It does this by modifying the exhaust valve timing to open at top dead center while cutting fuel. Once turned on all you do to engage it is to take your foot off the accelerator. That staccato popping sound is the compressed air blasting out of the exhaust valves.

On old rigs like my '61 Mack the jake brake is switched manually. You have to be sure to turn it off once you get close to engine idle rpms otherwise the engine will stall.

A quieter version called a bleeder brake which does the same thing though it leaves the exhaust valve slightly open during the entire compression stroke eliminating the popping sound. There is also the exhaust brake which puts a butterfly valve on the exhaust line creating back pressure when closed. Though the exhaust brake is known to cause problems with some valve train setups.

Re: Towing a Tesla at 70 MPH replenishes battery at fast charger rates

#357

Post by sokoloff »

kllrnohj wrote: post #174
sokoloff wrote: post #6

It seems like the tire wear wouldn't be worth it. You're pulling the tires at almost 100 horsepower of energy transfer. Sure, neat for a video gag though.

A Tesla will regularly put 100hp or more into just accelerating to highway speeds on an onramp. It's not exactly a tire-shredder.

For 10 seconds at a time, of course. Our old Honda does the same. Both of those actions do in fact wear the tires, but fortunately for drivers, neither car merges onto a highway for hours at a time continuously (such as charging a Tesla might).

Re: Towing a Tesla at 70 MPH replenishes battery at fast charger rates

#358

Post by cartoonworld »

alliao wrote: post #341
cartoonworld wrote: post #194

Earlier quoted context omitted.

Engine braking is definitely always much louder than regular braking. Don't piss off your neighbors. The bypass valve on semi's you're referring to is not the exhaust. The huge BRAAAAAAAP that you hear coming from trucks when someone cuts them off aren't an exhaust bypass valve, its them slamming on their brakes to avoid a tragic 20-car pileup. It is a release of the compressed air-fuel mixture momentarily before com…

do you know how does those volvo semis stop on a dime? are there some sort of destructive braking mechanism to perform emergency brake?

I'm not sure what you're referring to, sorry

Re: Towing a Tesla at 70 MPH replenishes battery at fast charger rates

#359

Post by dahfizz »

beerandt wrote: post #274
dahfizz wrote: post #263

Earlier quoted context omitted.

Literally destroying a mountainous environment is not clean energy.

But endless fields of solar panels and wind turbines is? That seems like a somewhat arbitrary, fine line to walk.

Those sources of energy are both renewable and can be deconstructed with no permanent environmental impact, which makes them "clean" in my mind but I agree it's an ambiguous word.

Re: Towing a Tesla at 70 MPH replenishes battery at fast charger rates

#360

Post by xattt »

cartoonworld wrote: post #252
xattt wrote: post #244

Earlier quoted context omitted.

I had a VW Golf with a DSG (DQ250) which I regularly engine braked on hills. However, I noticed that the instantaneous fuel economy meter would show some consumption on downshifting versus no consumption on coasting in drive. It turns out that the logic will try to rev match to be in a lower gear before cutting off the fuel again. Rev matching wasn't perfect either, as going down more than one gear would cause the en…

Ouch, lots of the VW fans I've known were die hard due in part to the ergonomics and feel of the manual transmission. Something about a cable I think. Too bad VW mechatronics doesn't read the throttle position for a clue here. It all just seems so obvious.

I think the rev matching to minimize the strain on the clutch pack. The car also had standard hill hold assist to minimize the risk of wearing out the clutch over a long period of time while living in a hilly area.

The design of the VW Golf Mark VII was absolutely brilliant. The EU model got a few why-didn’t-I-think-of-that extras that the NA market didn’t get, particularly around towing. There was a hidden tow hitch that popped out when a button on in the trunk was pressed, as well as reversing assist that used the electric mirror control knob (!) as steering control.

Post reply on HN