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

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

#211

Post by usrusr »

FridayoLeary wrote: post #78
ols wrote: post #56

The most spectacular example of regenerative braking are trains that are used in Scandinavia, heavily loaded with iron ore that is transported to the coast: "In Scandinavia the Kiruna to Narvik electrified railway carries iron ore on the steeply-graded route from the mines in Kiruna, in the north of Sweden, down to the port of Narvik in Norway to this day. The rail cars are full of thousands of tons of iron ore on th…

The heavy iron ore is essentially a large battery storing gravitational energy. In a way it's just another natural energy source. Maybe in the future clean power can be generated from pulling down mountains.

Melting down glaciers that subsequently pass through turbines on the way down should come close enough I guess? That future is here.

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

#212

Post by _carbyau_ »

sigstoat wrote: post #86
FridayoLeary wrote: post #78

Earlier quoted context omitted.

The heavy iron ore is essentially a large battery storing gravitational energy. In a way it's just another natural energy source. Maybe in the future clean power can be generated from pulling down mountains.

> Maybe in the future clean power can be generated from pulling down mountains. it takes a lot of power to dismantle mountains and load them onto trains. and folks get real grumpy about mining operations leveling off mountains.

And it sounds like a rather visible ... race to the bottom, as it were. :-)

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

#213

Post by lostapathy »

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.

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

#214

Post by adonovan »

shkkmo wrote: post #210
cartoonworld wrote: post #182

Earlier quoted context omitted.

This is commonly called power braking, usually called up in an emergency. It's a good technique that preserves handling. If you have RWD, your front suspension will remain more unsprung, in any case you can quickly apply the throttle to maneuver. The friction isn't what's working here, it is the compression of the cylinders in the engine draining momentum from the wheels, think of it as negative torque. As the forwar…

> 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.

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

#215

Post by ClumsyPilot »

avalys wrote: post #115
Guvante wrote: post #107

Earlier quoted context omitted.

So I did the math and the average water tower holds something like 1/2 kWh worth of power. (50m tall, storage of 1m gallons, efficiency of 90%) Hydro power storage is fantastic but needs truly ridiculous amounts of water and height deltas to make sense.

You’re telling me I could fill a typical water tower in 1 hour with a 500 W pump running off a kitchen outlet?

500W is a lot, it is hypothetically enough to move 10 liters of water 50 meters up every second. A motor on a cycle an electric bike is 250w.

A kitchen tap provides like what, 0.2 liters per second?

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

#216

Post by ClumsyPilot »

mikepurvis wrote: post #147
dharmab wrote: post #101

Earlier quoted context omitted.

Water towers are already used that way- water is pumped in during off-peak time and used during peak time.

Right, but that's about maintaining pressure and supply when everyone wants a shower at the same time in the morning, not about harvesting the energy of it all flowing downhill.

Pressure is energy

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

#217

Post by jborichevskiy »

Isn't this just transferring energy from the car towing to the Tesla itself? My understanding is this production of power induces some friction, that otherwise would've been closer to neutral.

In other words, if the wheels were completely free to spin, would not the towing car require less power to tow?

Or is my understanding of this off? Physics was a long time ago

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

#218

Post by bigiain »

jvanderbot wrote: post #191
FridayoLeary wrote: post #78

Earlier quoted context omitted.

The heavy iron ore is essentially a large battery storing gravitational energy. In a way it's just another natural energy source. Maybe in the future clean power can be generated from pulling down mountains.

A thousand (1e3) metric tons (1e3 kg) of anything, up a thousand meters (1e3), has 1e9x(10)=1e10 Joules of potential energy on earth (g=~10 m/s2). At 80% conversion (8e9 J) and assuming 1/8 of the energy is "payload" after paying for the train to go up, that's still ~1e9 or a GigaJoule. At a -20% grade, you're looking at a 5km train ride, which reasonably might take a half hour or less (1800s). So, you're generating…

A 20% grade is probably unachievably steep for ordinary railways. Even a 5% grade is considered remarkable.

Wikipedia says (https://en.wikipedia.org/wiki/Saluda_Grade):

Saluda Grade is the steepest standard-gauge mainline railway grade in the United States.[1] Owned by the Norfolk Southern Railway as part of its W Line, Saluda Grade in Polk County, North Carolina, gains 606 feet (185 m) in elevation in less than three miles between Melrose and Saluda. Average grade is 4.24 percent for 2.6 miles (4.2 km) and maximum is 4.9% for about 300 feet (91 m).

Unless you're gonna build that mountain style with gear drive and toothed tracks, you're probably looking at 5% grade and a 20km ride, which drops you down to ~140kW for 2 hours.

Ion the other hand, it seems you can get 11 thousand tonnes in a coal train:

https://www.australianmining.com.au/news/%E2%80%8Bnew-coal-t...

So on my 5% grade track I could get 1.5MW and if you can get your 20% grade to work that'd be just over 6MW

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

#219

Post by gpm »

dcanelhas wrote: post #105

They would clearly have been better off putting a diesel generator on a trailer behind the tesla, for fuel efficiency. 4 gal in 20 minutes the video said? That's about a 160kW generator https://www.hardydiesel.com/resources/diesel-generator-fuel-... I wonder how diesel generator + tesla compares to an actual diesel car.

Can you charge a tesla through the charging port while driving it?

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

#220

Post by cartoonworld »

olyjohn wrote: post #189
cartoonworld wrote: post #182

Earlier quoted context omitted.

This is commonly called power braking, usually called up in an emergency. It's a good technique that preserves handling. If you have RWD, your front suspension will remain more unsprung, in any case you can quickly apply the throttle to maneuver. The friction isn't what's working here, it is the compression of the cylinders in the engine draining momentum from the wheels, think of it as negative torque. As the forwar…

Your front end still takes the weight under any deceleration event. That's why FWD cars still squat in the rear on acceleration.

yes, it will always rock fore and aft to some extent, but consider the difference between applying a drag to the front of the vehicle or the rear. Try this on a bicycle if you have the time.

The "squat" you see on accelerating FWD vehicles is something different called wheel climb I think and is related to the effects of braking and center of gravity that we are discussing. When you gun the throttle, the wheel torque applies an opposite force as the wheels are turning in relation to the car. This causes a lever-like interaction forcing the front up and the rear down. During the engine brake maneuver the situation is reversed, as the torque is reversed in this scenario.

Imagine you had a car with independently activated front and rear brakes: Its trivial to understand that in a front-brake it will cause the front of the vehicle to tip forwards, and the rear will respond by tipping upwards. This unloads the rear suspension causing excessive camber, reducing tire contact, and if you were applying the brakes here, braking performance.

If you apply only rear brake, it will cause the rear wheels to pull their suspension downwards tipping the car rearward somewhat. As the stopping vehicle weight then pulls on the rear axle load, it applies a weak lever-like corresponding downward force on the front axle, reducing your center of gravity over the front-brake scenario. This will improve your handling performance, like I said.

Additionally, highway vehicles are designed with proportional braking that applies more of the braking force to the front rather than the rear. This, among other reasons, is why you can fishtail when you slam on the brakes. If you want to try it out, pull your ABS fuse the next time it rains, snows or there is some other slippery conditions and tool around in an empty parking lot.

This is why power braking is more suitable for RWD vehicles. It alleviates some of the effects of proportional braking and maintains a more favorable center of balance and suspension geometry.

It isn't that it doesn't work on FWD vehicles (It works well, and I did not mean to imply that it did not) only that RWD vehicles preserve more of their handling with this maneuver because of the facts regarding how a vehicle's suspension and center of gravity respond to braking and suspension load.

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