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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

#311

Post by fierro »

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…

probably not net positive if you factor in the energy required to load the ore onto the train at the top.

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

#312

Post by kijin »

fy20 wrote: post #258
codeismath wrote: post #164

Earlier quoted context omitted.

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…

True, but pumped storage can be made ridiculously large given favorable terrain. I've been to one that pumps 5 million tonnes of water up 800 meters (half a mile of head!), generating up to 1GW on the way back down. It probably costs less to maintain that thing than to charge and discharge an equivalent amount of lithium batteries every day.

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

#313

Post by iancmceachern »

rootusrootus wrote: post #253
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.

I too exist where the vent diagrams of HN reader and F250/travel trailer owners intersect.

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

#314

Post by matt-attack »

dahfizz wrote: post #273
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…

> 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.

The weight of the Tesla is moot. The majority of the load experienced by the pulling vehicle is in the incredible drag of the Tesla’s wheels. They’re extremely difficult to spin and this for pace far exceeds any others that would normally be encountered when pulling a traditional load.

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

#315

Post by dandelany »

fy20 wrote: post #258
codeismath wrote: post #164

Earlier quoted context omitted.

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…

Density isn’t everything. It’s likely a lot cheaper and less environmentally destructive to dig a big hole in the ground than to manufacture a lithium battery.

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

#316

Post by matt-attack »

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.

Remember that the weight of a load is entirely meaningless when pulling at a constant speed on level ground. The force experienced by the tower is entirely a result of air resistance and road friction.

On level terrain, the weight of the load is only relevant for the very transient period of coming up to speed. That is the acceleration phase.

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

#318

Post by watt »

anonporridge wrote: post #267
ryanmarsh wrote: post #243

Earlier quoted context omitted.

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

I love this measure of charging speed. I'm wondering now why I haven't ever seen it used before.

It is getting more popular, also because vehicles charging at same energy input (say, 100 kW) can show larger kmh value (or mh) depending on how efficient the car is: the more efficient car can go further on the same energy input.

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

#319

Post by polishdude20 »

unknown_error wrote: post #275
polishdude20 wrote: post #204

Earlier quoted context omitted.

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.

I don't think the passengers would appreciate getting back up via plate tectonics.

I mean, you provide a service to bring skiers down the mountain. You can let regular taxis bring them up

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

#320

Post by hunter2_ »

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…

> It's a good technique that preserves handling.

When traction is plentiful, yes. When approaching the limits of traction (in snow, or while turning, etc.), regular braking (or for curves, you could say trail braking) is usually best because the jerk of engine braking right when the clutch is engaged can upset the balance just enough to break loose.

That said, it does have an anti-lock effect in snow which is handy for cars that lack ABS, so as long as the jerk is accounted for, it can be a net win.

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