Earlier quoted context omitted.
Until the tow truck hits the brakes…
I was once involved in towing a car using a partially-inflated water bed as a 'bumper'. We got there!
Old tire not on a rim is the classic item to use for that use case.
Towing a Tesla at 70 MPH replenishes battery at fast charger rates
151–160 of 399 posts
Re: Towing a Tesla at 70 MPH replenishes battery at fast charger rates
#152Earlier quoted context omitted.
So I did the math and the average water tower holds something like 1/2 kWh worth of power. (50m tall, storage of 1m gallons, efficiency of 90%) Hydro power storage is fantastic but needs truly ridiculous amounts of water and height deltas to make sense.
You’re telling me I could fill a typical water tower in 1 hour with a 500 W pump running off a kitchen outlet?
Really good sanity check concept!
Re: Towing a Tesla at 70 MPH replenishes battery at fast charger rates
#153Earlier quoted context omitted.
That would be a neat test. Find a steep hill, preferably as straight as possible, and test how many times an electric car can traverse it before running out of batteries. Would the distance traveled exceed that on a flat road with no generation? By how much? I'm sure someone in San Fran has already tested this.
My intuition would say you'd never have longer range driving up and down a hill compared to driving flat in a straight line (and never braking). I would imagine that at best, you could maybe match the range. If there's any scenario where going up and down a hill would yield more range than driving flat, I'd be very interested in how/why.
There is a potential benefit, and it is not really due to regenerative braking. It would require that your traction system is more efficient at converting stored charge into kinetic energy at high loads than at medium loads and that it also has a very efficient "coasting" mode to cut losses when almost no output is required.
Cruising on level terrain is a mediocre load on the traction system to offset the rolling and aerodynamic friction. Climbing a steep grade at the same speed will increase the load significantly, but that extra kinetic output energy is being stored as gravitational potential energy rather than lost like the baseline cruising load. Then, when you descend the mountain on the other side, you recover that gravitational energy to offset the rolling and aerodynamic friction. You want to be "falling" down the mountain grade at your terminal velocity where no braking and no traction force is required to maintain your cruising speed. It will not work well for winding descents where you need to brake for turns.
I've seen this work with turbocharged ICE cars with elevation gains of 4k foot or more and hundreds of miles distance. I've repeated on many trips to prove to me that it isn't simply a fluke (such as extreme headwind or tailwind). Going over a pass yields me a better trip MPG than covering the same several hundred miles on relatively flat ground.
I could see this benefit for a hybrid car too, since I believe they mostly handle highway cruise on ICE power. However, it seems unlikely for a BEV car unless there is something about battery and power electronics that I do not understand, that would give them a significant efficiency boost at high power.
Re: Towing a Tesla at 70 MPH replenishes battery at fast charger rates
#154Earlier 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.
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.
Re: Towing a Tesla at 70 MPH replenishes battery at fast charger rates
#155Re: Towing a Tesla at 70 MPH replenishes battery at fast charger rates
#156Earlier quoted context omitted.
So I did the math and the average water tower holds something like 1/2 kWh worth of power. (50m tall, storage of 1m gallons, efficiency of 90%) Hydro power storage is fantastic but needs truly ridiculous amounts of water and height deltas to make sense.
You’re telling me I could fill a typical water tower in 1 hour with a 500 W pump running off a kitchen outlet?
[deleted]
Re: Towing a Tesla at 70 MPH replenishes battery at fast charger rates
#157Earlier quoted context omitted.
Not true, a rope is fine.
I don't think so. Most vehicles have virtually no braking power with the engine off. It's definitely completely forbidden in France to tow with a rope, and I'm pretty sure this applies to all or at least most of UE too. In Germany, even tow dollies are forbidden.
> Most vehicles have virtually no braking power with the engine off
You just need to press the brakes harder. Like 3 times harder, not 30.
If you park in a slope and turn the engine off you can try braking after pumping the vacuum out - it works just fine.
Re: Towing a Tesla at 70 MPH replenishes battery at fast charger rates
#158Earlier quoted context omitted.
That would be a neat test. Find a steep hill, preferably as straight as possible, and test how many times an electric car can traverse it before running out of batteries. Would the distance traveled exceed that on a flat road with no generation? By how much? I'm sure someone in San Fran has already tested this.
My intuition would say you'd never have longer range driving up and down a hill compared to driving flat in a straight line (and never braking). I would imagine that at best, you could maybe match the range. If there's any scenario where going up and down a hill would yield more range than driving flat, I'd be very interested in how/why.
It seems possible in theory. The air is thinner at higher altitudes, and wind resistance is a big part of fuel economy, isn't it?
Suppose you're going to make a 100 mile (160 km) trip. You have two possible routes. One is a straight shot on level ground. The other is straight, too, but it takes you up a 10% grade for the first 10 miles (gaining 1 mile in altitude), then you continue on level ground for 80 miles, and then you descend a matching 10% grade at the end.
It seems like the 80 miles of cruising on level ground at high altitude would use less battery than 80 miles of cruising at sea level (if the speeds are the same).
There will be some losses due to climbing and descending. Maybe climbing and descending is a little less efficient. Also, you're definitely traveling a very slightly longer distance. But those losses might be made up for spending the bulk of your trip in thinner air.
Re: Towing a Tesla at 70 MPH replenishes battery at fast charger rates
#159Regenerative 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.
Diesel engines in large trucks have a similar feature: https://en.wikipedia.org/wiki/Compression_release_engine_bra...
However, unlike regenerative braking, you won't end up with more fuel in the tank afterwards.
Re: Towing a Tesla at 70 MPH replenishes battery at fast charger rates
#160It seems like the tire wear wouldn't be worth it. You're pulling the tires at almost 100 horsepower of energy transfer. Sure, neat for a video gag though.
It is worth it if you run out of battery away from a charger.