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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

#241

Post by RyanPringnitz »

femto wrote: post #221
AceJohnny2 wrote: post #196

Earlier quoted context omitted.

> I love pumped storage, too bad it's not used more Pumped storage is awesome and the most cost-efficient way to store energy. It's used as much as possible, but... I attended a USGS [1] talk about dams (in California) a few years ago. The key takeaway is: all places worth damming have been dammed. There are no more dammable places, hydrologically and geologically speaking. When I drive through the central valley, I…

With pumped storage you don't need anywhere near the amount of water or storage needed for straight Hydro. In a 24 hour cycle, you can empty the top dam into the low dam, running the generators flat chat (unlike typical hydro which is limited by water supply), then pump it back up again for reuse. If you do the numbers (E=m.g.h) the amount of water required to store energy for a city of millions is quite tractable, a…

Another recent example in 2021. Kauai is supposed to be up to 80% powered by renewables with their pumped storage install. Small scale, but great example.

https://www.powerengineeringint.com/renewables/kauai-island-...

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

#243

Post by ryanmarsh »

_ea1k wrote: post #237
quickthrower2 wrote: post #207

Earlier quoted context omitted.

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.

The residence won't charge anywhere near as quickly as this, though.

The Tesla charger at my residence charges the car at ~30mph

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

#244

Post by xattt »

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…

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 engine to lazily rev up until it got close enough in speed before the clutches fully engaged.

The DSG offered a Sport mode (obviously to be used when late for work) that would downshift on deceleration, offering a mild form of automated engine braking. I could never quite tell whether would wearout the clutch packs or the brakes faster as it seemed to be a real push-pull scenario between the two.

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

#245

Post by ryanmarsh »

deadbunny wrote: post #173
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.

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.

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

#246

Post by photojosh »

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.

I'm surprised more people don't know that a very similar test has been done [0] (but not towing the generator, which would probably make it lose). Guess today is your lucky day to learn about it and I'm glad to be the one to inform you!

Spoiler: the Tesla+diesel generator wins.

[0] https://reneweconomy.com.au/tesla-ev-charged-with-diesel-gen...

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

#247

Post by millerm »

throwaway0a5e wrote: post #234
nimbius wrote: post #169

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…

>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.

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

#248

Post by AYBABTME »

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.

It doesn't refill your gas tank though, you just use the momentum, friction and heating up of compressed air of your engine to slow down, wasting all the energy of going downhill into heat.

EVs on the other hand get a partial refund for the energy they spent going uphill in the first place.

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

#249

Post by mjevans »

gregwebs wrote: post #228
AceJohnny2 wrote: post #196

Earlier quoted context omitted.

> I love pumped storage, too bad it's not used more Pumped storage is awesome and the most cost-efficient way to store energy. It's used as much as possible, but... I attended a USGS [1] talk about dams (in California) a few years ago. The key takeaway is: all places worth damming have been dammed. There are no more dammable places, hydrologically and geologically speaking. When I drive through the central valley, I…

I think you are describing pump-back hydro dams which are only a subset of pumped storage. Strictly speaking pumped storage only requires an elevation change and a water supply

If not near a water supply or lack of intent to use some of the pumped water for irrigation anyway, as the parent post said, (nearly) everywhere it was worthwhile to do is already doing it.

The alternative is another form of gravity battery, often involving railway on a hillside and cars loaded with stone.

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