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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

#301

Earlier quoted context omitted.

I do wish the Tesla would turn on the brake lights when slowing down at a certain rate (due to regenerative braking). I've nearly been rear-ended several times by cars that didn't expect me to "coast" that slowly or, conversely, slow down that fast without brake lights.

They do

Yeah, I was worried about this and so I watched the lights on the visualization: at least per the visualization, the brake lights are turn on for regenerative breaking more or less like they would turn on for applying the brakes.

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

#302
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…

An older strategy was to connect ore cars together so that the full train going down hill would pull the empty train going up hill. It was depicted in The Railway Series

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

#303
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…

ARES (Advanced Rail Energy Storage) has been trying to commercialize purpose-built facilities of this type, with the first currently under construction in Nevada. They've gone through a number of design revisions but what they're building right now seems just just be multiple-unit trains full of gravel on straight lines. They've also proposed a system of autonomous trains loading and unloading concrete blocks via switchyards, but I imagine they are holding off on this more complex design for a larger installation, and the current site is a gravel quarry so they're using native materials. Advertised efficiency is over 90% at 5MW per rail line.

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

#304

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.

Vehicle to vehicle charging is another option. E.g. the new Rivian will support that and several other recently announced cars feature the ability to power external things. Tesla might go there too with e.g. the new cybertruck and other vehicles. And of course using batteries is also a thing for emergency charging services you'd call in if you actually do run out of juice.

The rare driver getting caught completely ignoring their car's warnings that they are running out of power all the way down to zero would have a few options beyond calling in a tow truck. Even just rolling it down a hill would work.

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

#305
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.

> 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.

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

#306

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.

I read somewhere that this was how Chevrolet came up with the Volt concept. They were working on an electric car prototype, and to save charging time at the track, they threw a gas generator in the trunk. They were surprised to find it worked reasonably well. I don't know whether this story is true, though; tonight I couldn't find a source.

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

#307

Earlier quoted context omitted.

Range extenders exist. The 2014 BMW i3 offered one as an option. But now that batteries can provide 200+ miles of range there's less need for them and most EV companies have stopped making them. (Of course this hasn't stopped people from building their own.) https://www.autobytel.com/car-ownership/technology/what-is-t...

Even for high range cars, this makes so much sense to me. The biggest situation keeping me from getting an electric truck right now is towing something long distance since it kills your range, and often the long distance is way out in the middle of nowhere away from any chargers. This might be oversimplified, but trains have been giant diesel generators powering electric motors for decades now, so why not add diesel…

It does make sense if you need a car with extra-long range. Locomotives are diesel/electric hybrids not specifically because of range but because they need the torque that only electric motors can provide. If it was only about range, trains would just run directly on diesel engines.

Until recently batteries with the energy density needed for trains didn't exist, so the diesel generator was a necessary part of the equation. That is changing however, and battery/electric trains are now being tested.

https://www.bnsf.com/news-media/news-releases/newsrelease.pa...

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

#308

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.

Years ago I visited the Seneca Pumped Storage Generating Station [0] reservoir in person. It's a massive man-made lake on the top of a small mountain in Pennsylvania, USA. They pump water up to it at night (when there is excess energy in the power grid), and let the water out in the day when the demand for energy is high (turning some turbines on its way down). Prior to visiting I had an intellectual understanding of…

As Swiss friend once told me that Switzerland have super cheap electrical power by buying surplus power from the french nuclear power plants in summer and pumping into reservoirs high in the mountains.

Never verified the story, but geography checks out.

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

#309

Earlier quoted context omitted.

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…

> If you apply only rear brake, it will cause the rear wheels to pull their suspension downwards tipping the car rearward somewhat. Are you sure? I'm trying to draw a free body diagram of that, and I get a net moment tipping the car forward. Can you explain it using physics principles? > Try this on a bicycle if you have the time. You can't easily compare because the rear wheel easily skids with a fraction of the bra…

> Are you sure?

Yes.

It's pretty confusing, I did the same thing and came up with the same answer as you. Then I typed a sentence about "even on fully independent multi-link rear suspensions" before going off into the weeds. If the suspension were rigid, it seems like it should do the opposite, climbing upwards, but there is more going on in the car than the assumptions we typically make with a model.

A rear suspension is of course not rigid. It is, in short, a vertical damped spring mounted on a lever attached to the frame in front of it's axis. The axle/wheel hub is attached to the bottom of this damped spring at the end of the lever.

During braking, the rear will deflect rearwards and also be drawn towards the centerline of the vehicle following the arc of a circle drawn on the ground. The suspension will control the forces through the trailing arm, directing them towards the rear along a second arc drawn on the side of the vehicle, centered on the rotational vertex where the trailing arm is bolted to the car in front of its axle. The sway bar will control both sides to the same level which will be the apogee of the circle, closest to the rear bumper.

You can test this by pulling your parking brake below 5mph. If this doesn't work, call your mechanic :)

>You can't easily compare because the rear wheel easily skids with a fraction of the braking force the front wheel can take.

That is because braking the front bike wheel causes the lever to apply an upward force on the rear axle, pulling the front wheel rearwards, causing absurd instability and poor handling. This also happens to the rear wheel, it wants to hop upwards in response to the brake forces. That's why the proportional brakes exist in highway vehicles, to stabilize the braking forces into the most efficient braking scenario. If the front wheel were mounted in a reverse mounted trailing arm suspension (This doesn't exist, so I don't know what else to call it.) it would drop the front of the bike as happens to a car instead of flipping you off the bike. The side effects of this are atrocious understeer and a nonsensical center of gravity.

The reason the wheels move like this is to control for a characteristic called caster. Bikes have negative caster, if you let go of the handlebars at low speed, they will flop to one side or another at random, causing you to crash. Cars have positive caster which is the most stable configuration for the steering to operate. This is also why your steering wheel returns to center when you let go of the wheel while moving forward, and it is why the braking forces can be stabilized in this manner.

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

#310
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…

Same as this truck..

This Huge Electric Dump Truck Never Needs to Plug In

https://www.wired.com/story/this-huge-electric-dump-truck-ne...

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