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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

#201

Post by jvanderbot »

calvinlh wrote: post #199
jvanderbot wrote: post #191

Earlier quoted context omitted.

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…

You're off by a factor of 3600-- 1 watt is a Joule/second, not a Joule/hour. 1 GJ / 1800s ~= 555kW, not 2GW.

I knew it seemed high. The GW description didn't match the wikipedia article.

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

#202

Post by quickthrower2 »

spurgu wrote: post #154
lwansbrough wrote: post #110

Earlier quoted context omitted.

This idea is sort of being explored already: https://www.youtube.com/watch?v=itbwXMMkBQw There's other ways of doing this too. Rolling a ball up a hill, inflating a balloon under water, etc.

That looks like a real life battery level indicator.

My take: it's cheating at jenga.

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

#203

Post by ricardobeat »

worldsayshi wrote: post #129
danboarder wrote: post #63

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…

That sounds quite clever! Another potential for low cost infrastructure in remote places.

It's unlikely that a dyno + all the associated infrastructure would be lower cost than a 150kW charger - they cost ten to twenty thousand dollars apparently.

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

#204

Post by polishdude20 »

hourislate wrote: post #51
codeulike wrote: post #48

Earlier quoted context omitted.

Would the distance traveled exceed that on a flat road with no generation? No. Climbing the hill the car uses extra energy (compared to a flat road) because its fighting gravity. On the way back down the hill regen will recover some of that gravity-fighting energy but nowhere near all of it.

This scenario is a little different than a car but a Swiss company is experimenting with a Komatsu Dump Truck that basically recharges its battery using regen braking on it's trip down so it has enough power for the trip up. It actually generates a surplus of an extra 10kwh because the truck is carrying a full load down. https://phys.org/news/2017-09-e-dumper-world-largest-electri...

What if you did this with passengers instead of a truck load of rocks? Carry passengers down a mountain, go up the mountain with an empty tesla.

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

#205

Post by nixpulvis »

A friend of mine recommended I watch this video after I was asking him about the limits of these things: https://www.youtube.com/watch?v=oJL9MasBFvM&ab_channel=Engin...

I attempted to summarize below:

"ah yes, it's because the batteries take up a vastly large percentage of the vehicles weight. For towing (hauling?) this is a critical figure, whereas it generally doesn't matter for a passenger car.

That said, IIUC, this is equivalent to range, it's just that many gas cars choose to sell lower percentage weight tanks since they go plenty far already, and that way you accelerate faster."

Sorry for the strange comment style.

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

#206

Post by hardwaregeek »

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.

Energy Vault is a startup that stores energy using big concrete blocks. Pretty close to your idea: https://en.wikipedia.org/wiki/Energy_Vault

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

#207

Post by quickthrower2 »

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 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.

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

#208

Post by r00fus »

JimTheMan wrote: post #163
ElijahLynn wrote: post #160

Earlier quoted context omitted.

It is worth it if you run out of battery away from a charger.

I anticipate a future where mobile road repair will carry their own massive batteries by default to restart dead EVs on the side of the road.

It'd be nice if those vehicles also were hybrids that could use the gas power plant to regen the aforementioned batteries.

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

#209

Post by elihu »

saalweachter wrote: post #187
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…

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.

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.

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

#210

Post by shkkmo »

cartoonworld wrote: post #182
asdff wrote: 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…

> 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.

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