New Mars Forums

tahanson43206

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Registered: 2018-04-27

Posts: 19,393

Tesla Automobile Service

In several topics in this forum, SpaceNut has occasionally provided updates on maintenance of a piston powered automobile.

This new topic is offered because none of the several topics containing the keyword "Tesla" seemed a good fit.

In another topic, I reported my observation that my neighbor (a) has a Tesla and (b) she is using ordinary household current to re-charge it.

Today, I got another chance to learn something about Tesla automobiles ...

I had gone out to the alley to drop some items in the waste pickup container, and arrived there just as a Tesla drove up to my neighbor's garage.

The arriving vehicle turned out to contain a Tesla home service representative, with both the front and rear storage locations filled with test equipment and spare parts.  Later on I observed the technician under the front dash with a bright flashlight.

After a period of time while I did chores out front, I returned to the alley just as the technician drove off with a wave, and I saw the neighbor's vehicle charging again, before the garage door closed.

While I recognize this single observation is NOT more than a single data point, hopefully it will inspire other forum contributors to add their observations or perhaps reports about what it takes to keep a Tesla running.

(th)

SpaceNut

Administrator

From: New Hampshire

Registered: 2004-07-22

Posts: 29,431

Re: Tesla Automobile Service

Found a few posts that reate to th vehicle and powering of it

The 5 seats (includes 1 driver) Tesla Model S (P100D variant) weighs 4,960lbs (without passengers).  If you remove the electronic governor, you can hit about 200mph.  At that speed, your battery pack has a matter of minutes of charge.  I doubt you'd make it 100 miles at that power output level.  The Model S battery pack weighs 1,056lbs and stores 100kWh.

The 10 seat (includes 1 pilot) Pilatus PC-12NG weighs about 10,450lbs (full fuel and passenger load), so roughly twice the weight of the Tesla if you include the passengers in the weight of the Tesla.  This particular bird cruises at over 300mph and can cover just over 2,120 miles at best cruise speed with sufficient fuel reserves for VFR flights.  The full fuel load weighs 2,704lbs.  At that weight, an equivalent set of 66lb Tesla battery pack modules would provide 256kWh worth of electricity. 
An aftermarket aircraft conversion company creates a new battery and electric motor powered variant of the Pilatus PC-12NG.  This variant stores 256kWh worth of electricity in its Tesla Motors battery packs instead of 2,704lbs of Jet A used by the turboprop powered variant.

What do batteries store now?: 260Wh/kg - Tesla batteries (actual commercial production technology)

The reason EV motors use high voltages is to diminish resistive losses (electricity converted to waste heat) during power transmission and to reduce the diameter and thus mass of the copper conductors.  The electric motors found in Chevrolet and Tesla electric vehicles are all in the 300V+ range and higher voltages are quite common in EV racing motors.  Google "YASA Motors" for examples of high voltage EV motors.  Although YASA's motors are intended to run at high RPM, motors can also be designed to make nearly all of their torque at much lower RPM ranges.  DARPA has funded development of motors for electric aircraft that are excellent examples of motors designed for lower RPM ranges.

The depth-of-discharge issue applies to every battery, but Lithium-ion batteries are designed to discharge 80% of their rated capacity and that's what all manufacturers test against.

SpaceNut

Administrator

From: New Hampshire

Registered: 2004-07-22

Posts: 29,431

Re: Tesla Automobile Service

The secret to the telsa battery is in how its constructed to keep from catching fire...by small cells that have cooling built in to wick the heat away....

tesla battery pack images

The low level discharge is for storage and not use levels....when you discharge li-ion batteries that far you risk damaging the cell structure causing a barrier to charging to form which can cause the battery to short and not charge to full capacity. Recomended discharge in operation is only to 70% of its value before recharging....

http://www.techrepublic.com/blog/five-a … tery-life/

Characteristics of Rechargeable Batteries

Safe Lithium-ion Battery Designs for Use, Transportation and Second Use

Guidelines on Lithium-ion Battery Use in Space Applications

SpaceNut

Administrator

From: New Hampshire

Registered: 2004-07-22

Posts: 29,431

Re: Tesla Automobile Service

The small cylindrical Lithium-ion batteries that Tesla uses in vehicles, which have better energy density than prismatic cells, also have poor cold temperature charge / discharge performance in comparison to Yardney's prismatic cells, which is why NASA doesn't use them for any of their robotic missions to Mars.  None of the cells with the chemistry used by Panasonic and Tesla have passed testing thus far, as they'd be unable to charge or discharge at a sufficient rate to store enough of the power output from a solar array without first expending more energy to heat the cells to a temperature within their operational temperature design limitation

The EFOY Comfort direct methanol fuel cell, a real commercial product, can use 8.4kg / 10L / 2.64 US gallon methanol jugs that contain enough methanol fuel to supply 11.1kWh worth of electricity.  That equates to an energy density of 1,321Wh/kg.  The EFOY 210 model fuel cell itself weighs 8.5kg.  That does lower the effective energy density of the entire solution, but adding additional jugs of methanol rapidly outstrips the energy density of any battery-based solution, to include military and aerospace single use / primary type batteries.

The Tesla batteries store 250Wh/kg, not including any packaging or control electronics.  The Tesla Model 3's 75kWh battery pack weighs 1,054 pounds (a pair of 191 pound packs and another pair of 207 pound packs), not including the control electronics and power conversion equipment.  Approximately 18 gallons of methanol would provide 75kWh worth of energy using EFOY's fuel cell and it would weigh 126 pounds.  Therefore, the Tesla solution is more than 8 times as heavy for equivalent energy density.  The weight of batteries is a deal breaker for both aircraft and heavy transport vehicles that have strict weight limits imposed by simple physics and/or roadway gross vehicle weight rating limitations.

The most advanced super capacitors in commercial production have energy density (specific energy) in line with Lead-acid batteries.  However, these are still pretty expensive and applications remain limited.  Tesla Motors Corp purchased Maxwell for this technology.  Some dev lab 3D super cap technology has reached energy densities as high as 110Wh/kg, or a little less than half of what a commercial Lithium-ion battery can store.  It's an interesting technology for providing bursts of power for very brief periods of acceleration for motor vehicle applications, but not so interesting for powered flight applications which have high constant power requirements.  Trying to power any type of aircraft with Lead-acid batteries isn't very practical.

Super capacitors are capable of dumping stored energy at rates that would destroy Lithium-ion batteries.  A super capacitor bank is a good way to put less wear and tear on a Lithium-ion battery bank from very high discharge rates (for a battery) associated with very brief periods of acceleration measured in seconds.  The battery only has to recharge the capacitor bank and maintain a comparatively minor constant output level to move the vehicle at highway speeds (10hp to 20hp for most passenger vehicles in the 1t to 3t range).  So long as ranges of hundreds of miles are not required, you can make a battery powered motor vehicle lighter and cheaper because you don't need extra battery capacity just to deal with high discharge rates.  The same concept would apply to combustion engine vehicles.  If a vehicle was powered by a combination of super capacitors and a piston engine powering a generator, then a very low displacement engine combined with a super capacitor bank would be sufficient to accelerate the vehicle acceptably well and run it at highway speeds without requiring additional engine power for acceleration.  A free piston engine with a super capacitor bank would be ideal, I would think.

SpaceNut

Administrator

From: New Hampshire

Registered: 2004-07-22

Posts: 29,431

Re: Tesla Automobile Service

tesla battery charging station business oportunity topic

Lithium used for batteries

Now onto the battery. A battery that has been charged to full will need to be brought back down to the storage charge level of 75-80 of the working cell voltage range. examply of a single lithium voltage when full for a 3 volt cell is near 3.6v but a dead cell is near the 2.7v level. So a discharged battery readied for packaging will read about 3.1v for long term storage, to which they need a full 8 hours typically to recharge to full levels.
Lithium will not like a constant trickle charge as they will open internally from being overcharged if connected all the way to mars, to which they usually make a draw down circuit within the charger to be able to condition the cell for each use.
The story is about one or the other of the limits of use has been exceeded internally to the batteries normal operation. This is not only the stories vendor but all of the lithium battery types.
U.S. regulator to send observer for Tesla probe of Model S fire

This was the crash

This one happened while driving just before its parked

This one was whjile connected to the charger

The power bank is an ac device storage and since mars is a dc world until an invertor is turned for the device to operate will not be storing any excess power.

The other part of the battry issue is the temperature range for use on mars may be to cold on them causing them to short out as well.

SpaceNut

Administrator

From: New Hampshire

Registered: 2004-07-22

Posts: 29,431

Re: Tesla Automobile Service

For any vehicle, but especially a lightweight personal transport vehicle, aerodynamic drag force is considerable and typically more than rolling resistance.  Now you know why Tesla's engineers spent so much engineering effort on reducing the drag coefficient.  The Cd of a Tesla Model 3 is 0.23 and he frontal area is 23.9ft^2.  Those are impressive numbers, BTW.  Many bullets don't turn in a Cd that good.

23.9(frontal area in square feet) * 0.23 (Cd) * 23.5 (pounds of constant aerodynamic drag force at 70mph per square foot; doesn't change for different vehicles; only changes with elevation and temperature- atmosphere is thinner the higher you go) = 129.1795lbf (pounds of drag force that the motor must overcome to keep the vehicle at 70mph)

Now we add to that the rolling resistance / drag force produced by the vehicle's tires (this increases with increasing speed, but increasing tire pressure has a drastic effect on rolling resistance; the engineering toolbox website has a good graphic that shows the curves for tire inflation pressure and speed)

0.02 (rolling resistance coefficient at 70mph) * 4,100lbs (Model 3 mass with the 75kWh battery) = 82 pounds of force from rolling resistance

129.1795 + 82 = 211lbf

That's the drag force that the electric motor and battery have to overcome to keep the Tesla Model 3 at 70mph.  More power will be required going up a hill and less power will be required going down a hill.

The equation for horsepower (1 brake horsepower is 550ft-lbs/sec) required would be as follows:

211(pounds of force to overcome) * 102.667(fps at 70mph) / 550 = 39.386hp = 29.37kW

In other words, a Tesla Model 3 with the 75kWh battery pack could maintain that speed for 2.55 hours or 153 minutes.  Please note that for maximum range, according to mileage claims, you obviously can't travel at 70mph, because aerodynamic drag force goes up dramatically as speed increases.

SpaceNut

Administrator

From: New Hampshire

Registered: 2004-07-22

Posts: 29,431

Re: Tesla Automobile Service

Tesla's progress on batteries by louis

Tesla Cybertruck by Oldfart1939

Want an electric car? These states will pay you to buy a Tesla

Most people believe that a Tesla is out of their price range. With prices starting at $35,000 and going up to $124,000, the brand is definitely in the aspirational range for a lot of people. However, many states offer rebates and other incentives to buy electric vehicles, or EVs. The federal government also offers an income tax credit of up to 26% for green cars that run on alternative fuels, as well as for home utilities.

Some states even give you an additional discount for cars with solar and energy storage. If you're in the market for a new car, and you'd like to green your drive, you can find out here if your state offers discounts for buying an electric or alternative fuel vehicle. Note that discounts and rebates are subject to change.

https://www.fueleconomy.gov/feg/taxevb.shtml

29 slides of the states that have discounts

Looks like these are around only 2000 off

SpaceNut

Administrator

From: New Hampshire

Registered: 2004-07-22

Posts: 29,431

Re: Tesla Automobile Service

Kuka robots work on Tesla Model X in the Tesla factory in Fremont, California

Musk Urges Tesla Workers to Boost Output Through End of Year but Tesla Needs To Increase Production Now, Elon Musk Says In Leaked Email

Tesla tells employees Model S and X production will shut down for 18 days
But the media also has said he is moving his plants to Texas...
Of course those that lose there jobs are not going to help him make his numbers....

Elon Musk Promised 1 Million Tesla Robotaxis by the End of 2020. Where Are They?

There's no question that Tesla's advanced driver-assistance systems are very good. That doesn't matter, however, if the roads aren't ready, and not even Tesla is prepared for a broad rollout of level 5 vehicles.

The AI cars have crashed into non unmanned vehicles in several cases..

With others jumping into the automotive making
Nio joins Tesla and other rivals in rush to offer more shares in electric-vehicle companies

All that I can say is this is not fixing America's automobile industry.....

SpaceNut

Administrator

From: New Hampshire

Registered: 2004-07-22

Posts: 29,431

Re: Tesla Automobile Service

Bump
Have moved topic as it relates to a technology or science to the folder that contains a standardize system that would apply to mars.