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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

#251

Post by neon_electro »

asdff wrote: post #127
lapetitejort wrote: post #12

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.

Now try regenerative braking in an electric car. The 70kW regenerative braking ability of the Chevy Bolt is amazing on any downhill stretch. To the point that I can set a cruise control going down a mountain and actually maintain that speed without applying friction brakes.

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

#252

Post by cartoonworld »

xattt wrote: post #244
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…

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.

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

#253

Post by rootusrootus »

crackercrews wrote: post #118

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

I'm surprised it was that good. I get 8 MPG from my F250 when towing a travel trailer that doesn't have the brakes engaged.

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

#254

Post by rootusrootus »

millerm wrote: post #247
throwaway0a5e wrote: post #234

Earlier quoted context omitted.

>A Tesla model S is around 5000 pounds A whole host of 90s pickups are ~5000lb depending on how they're spec'd out. The Model S is fat. But so are a lot of other modern cars so whatever. 5k isn't that much at the end of the day though. Perfectly within the bounds of what a scrapper or farmer will tow with a compact truck. >not too shabby compared to your long-haul tractor trailers that get about 6 Heavy trucks punch…

But it’s not just 5k lbs free rolling. The regenerative brakes are an opposing force and increasing the load. So, it could be equivalent to 10k lbs. I have no idea how to calculate that though.

> So, it could be equivalent to 10k lbs. I have no idea how to calculate that though

It wouldn't have a good equivalent mass, since it would be entirely through rolling resistance that you'd get that equivalency. A better comparison would be wind resistance.

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

#255

Post by rootusrootus »

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.

Talking a little bit out of my ass here making some assumptions, but I'd guess that in this context, 'power braking' refers to grabbing an low gear and letting out the clutch to assist the front brakes when you're trying to stop really fast and maintain the handling dynamics of the car. It's hard to explain, but if you've driven a manual sports car for a while it's easy to learn. And it isn't the same as simple engine braking, which is usually done in higher gears to add moderate resistance, not to actually try to slow the car significantly.

And you do have to be careful not to grab too low a gear and/or don't let the clutch out too fast, or you can mechanically overrev the engine.

IMO compression braking (jake brake) would be a better analog.

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

#256

Post by slipframe »

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.

Clean power and mountaintop removal are mutually exclusive. That is neither clean nor renewable. Among other things, the water that flows through mineshafts, collects in quarries, or over strip-mines is often toxic as hell. When you dig into the rock like that, you expose a lot of water soluble toxic shit to the elements which poisons everything downstream.

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

#257

Post by darig »

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.

> Maybe in the future clean power can be generated from pulling down mountains.

why do you think mars is mostly flat?

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

#258

Post by fy20 »

codeismath wrote: post #164
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.

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…

The idea of pumped storage is pretty simple, but compared to lithium batteries the energy density is ridiculously small. If you already have an area that can be used for it (abandoned mine or reservoir) then it's pretty simply technology to build, but otherwise it's probably not worth it.

As an example of how low density it is, imagine having a 1000l IBC tank, filled with water, on your roof at a height of 10m. That water (~1000kg) has a potential energy of 98000J or 27Wh - less than a laptop battery :D

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

#259

Post by nomel »

asdff wrote: post #127
lapetitejort wrote: post #12

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.

My Toyota car, with an automatic transmission, does this automatically after it detects I've been riding the brakes for some time while going down a hill.

Coming from manual transmission, I was super excited when it happened the first time.

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

#260

Post by Matheus28 »

ryanmarsh wrote: post #245
deadbunny wrote: post #173

Earlier quoted context omitted.

I got pulled over for this. I was driving home from a friend's at about 2am so nothing but clear roads, it was on about a 10 mile stretch of dual caradgeways with a few roundabouts along the way. At the 3rd roundabout I got the flashing lights and dutifully pulled over. Turns out they pulled me over because they thought my break lights were out. After a quick demonstration of my fully working break lights and a quick…

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
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