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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

#181
post #132

Earlier quoted context omitted.

I've sometimes wondered if it would be viable to build a "range extender" for electric cars which is basically a generator which is designed to integrate with the vehicle, but can be easily removed. Then people could fit them when they were going on longer trips converting the car to a plug-in serial hybrid. Car dealerships could perhaps rent them out and do the install/removal.

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 generators to cars?

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

#182
post #127

Regenerative braking is so neat. I drove up a steep windy road to go on a hike with my plugin hybrid. On the way down I tried to let gravity do all of the acceleration and regenerative braking do all of the deceleration. At the bottom of the hill I had racked up +3 miles in total. Another fringe benefit is that brake pads wear out slower and produce less pollution.

You can get this sort of benefit with a gas car with a manual transmission too. Engine braking uses no gas, its just your wheels turning your pistons and the friction from all of that slows the car down. Most of the time I only hit the brakes to go from 5mph-0mph in a manual car thanks to this.

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 forward momentum of the vehicle causes the rotation of the drivetrain to begin to overcomes the speed of the engine output shaft at the clutch or torque converter, torque is effectively being reversed. Instead of engine output pushing the rotation of the transmission, the forces invert causing the transmission to drive the engine speed upwards. Most ECMs will recognize the zero throttle position and cut off fuel, but older vehicles may not have this capability and especially carburetor fed motors are mostly incapable of reducing fuel delivery in this manner.

If you need to stop quickly and have the time, you can downshift even in an automatic, just throw it into 3 or maybe 2 while braking. If you have an electronic dual-clutch transmission with a "manual" mode, the electronic management controls will prevent the engine from over revving and causing damage.

Its important to keep the RPMs low if you do this a lot, if you redline, you redline no matter what your intentions are. I'd wager that running your ICE at 80-90% redline at low speeds for extended periods is also going to affect longevity.

There are other effects you might notice, such as additional bump and over/under steering as your suspension geometry responds to the unusual load. Also, other components will become loaded in usual ways during this maneuver causing some possibly unexpected handling characteristics to present themselves. Its good to practice this in a safe location, before employing it in the field.

If I may venture to say, it gets even more interesting; some vehicles are constructed in a manner where this happens all the time, the old school Porsches were notorious for an effect known as "Throttle Steer", a description of which exceeds the scope of this post, but a curious person will find several references to this in automotive literature.

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

#183

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…

> one BIG BATTERY

> The power plant, rated at 451 MW

That's a damn big battery. I love pumped storage, too bad it's not used more.

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

#184

Just a little conjecture here, but i find the whole experiment fascinating. A tesla model S is around 5000 pounds. not the lightest car on the road by any standard...but towing it behind a consumer Ford F150 will drag the mileage of the truck to 14MPG. not too shabby compared to your long-haul tractor trailers that get about 6...but thats the free rolling weight of the vehicle, not its weight with regenerative brakin…

I think you have just described something like a traditional or plug-in hybrid that recovers energy that would be wasted under braking or puts the ICE under additional load to keep the specific fuel consumption as low as possible

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

#185

The Mercedes got 5 MPG while towing the Tesla at freeway speeds. [1] 1: https://youtu.be/nILM_DEdBqM?t=336

Makes sense. A MB C200 has 135 kW max from the engine, the Tesla’s battery is taking half of that, and losses in the energy transfer would be extra.

I don't think you have much losses in the transfer, the strap is probably efficient. Although they would be extra so you are correct.

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

#186
post #127

Earlier quoted context omitted.

You can get this sort of benefit with a gas car with a manual transmission too. Engine braking uses no gas, its just your wheels turning your pistons and the friction from all of that slows the car down. Most of the time I only hit the brakes to go from 5mph-0mph in a manual car thanks to this.

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…

[deleted]

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

#187
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…

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.

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

#188

So he was getting supercharger speeds (50% battery in about a half hour) which is awesome! The Tesla has its own built in "supercharger" if you can find an alternative way to power it. My idea then is this - could a dyno be modified to be powered and function as competitive to a Tesla supercharger? Basically towing it in-place. It would be rad to see this work! I could imagine connecting it to a geared waterwheel for…

No, it quite explicitly states this is "fast" (e.g. home) charging and NOT even v1 supercharger speeds.

"putting back electricity into the batter at a rate of 65 kW - not quite Supercharger speeds, not even V1 or V2 Superchargers that could muster up to 150 kW, but still pretty decent."

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

#189
post #127

Earlier quoted context omitted.

You can get this sort of benefit with a gas car with a manual transmission too. Engine braking uses no gas, its just your wheels turning your pistons and the friction from all of that slows the car down. Most of the time I only hit the brakes to go from 5mph-0mph in a manual car thanks to this.

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.

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

#190

Earlier quoted context omitted.

Makes sense. A MB C200 has 135 kW max from the engine, the Tesla’s battery is taking half of that, and losses in the energy transfer would be extra.

I don't think you have much losses in the transfer, the strap is probably efficient. Although they would be extra so you are correct.

GP almost certainly meant losses in the transfer from mechanical energy to chemical energy by way of the cars motors being used as generators, then charging the batteries.
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