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"It's A Brick" - Tesla Motors' Devastating Design Problem

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Re: "It's A Brick" - Tesla Motors' Devastating Design Problem

#31

Post by grannyg00se »

This is akin to leaving the headlights on when the car is turned off in a regular car. You're asking for trouble. (though not to the tune of $40,000)

When the car is turned off, there should be some kind of indication of how long it will take to brick the thing. If that indication is days rather than weeks, it should yell at you. Loudly. At least that way all owners will know of the threat. The car will educate them. (important, because they probably won't RTFM)

Although I'm sure you could still end up with the odd user who leaves the car with a three week brick time, receives no loud warning because of the significant charge remaining , comes back five weeks later and curses Tesla.

Re: "It's A Brick" - Tesla Motors' Devastating Design Problem

#32

Post by DrStalker »

simcop2387 wrote: post #22
MBCook wrote: post #21

Earlier quoted context omitted.

That seems like something that should really fail open, for exactly those kind of situations.

I dunno, that would mean that a bricked roadster on a hill would possibly roll away.

Failing open would be bad, a "unscrew this small panel and pull this switch" would be fine.

My car is old Saab and there are places to move aside bits of trim to manually operate the sunroof and fuel tank cover if the battery is completely gone.

Re: "It's A Brick" - Tesla Motors' Devastating Design Problem

#33

Post by jws »

noonespecial wrote: post #26
bradleyland wrote: post #15

Earlier quoted context omitted.

The account of the Tesla discharging while plugged in to a 100-foot extension cord strikes me as suspect. It's anecdotal at best. Have a look at the Tesla Roadster "Charging" page: http://www.teslamotors.com/goelectric/charging Using 120V @ 15A, you get a charge rate of +5 miles (of range) per hour. Obviously not the optimal solution, but not a net negative either. Adding a 100 foot extension cord isn't going to dimi…

120v @ 15A is 1800 watts. As I said, I was able to measure the wattage being delivered at the end of my 100 foot 16 gauge "home depot" orange extension cord connected to a space heater and found less than 900 watts being delivered to a load that normally pulls 1750. The voltage had also dropped below 100 volts. Its possible that the Tesla simply won't charge at all if the current or voltage on the line becomes too lo…

The pack is 53kWh according to wikipedia and discharges in 11 weeks from full according to the article. Unless I botched a decimal place, that is a 29 watt idle load. (53000 watt hours / (11 weeks * 7 days/week * 24 hours/day) ). In perspective, that is about the same as 4 night lights.

Clearly there is about 20 times that much power available at the end of a 100 foot extension cord in a standard household outlet.

Failure modes available:

• Was not actually plugged in.

• Was unplugged then plugged back in much later, possibly unbeknownst to owner. (Someone in my household unplugs my DVR to use an outlet. Grr.)

• Was on a switched outlet. (I once bought a new drill over that. Who knew one of the duplex outlets was switched and the other not? But the new drill wasn't $40k.)

• The Tesla charger could have a cutoff where it stops charging if unable to pull X amps where X is somewhere between 7 and 15. This could be either intentional or unintentional. Brown out protection circuitry, if needed by the design, could do this. They also might fear they are setting your house on fire by dropping 800+ watts somewhere in a wall and shut off.

• Broken charger.

• Broken extension cord.

Re: "It's A Brick" - Tesla Motors' Devastating Design Problem

#35

Post by bradleyland »

noonespecial wrote: post #26
bradleyland wrote: post #15

Earlier quoted context omitted.

The account of the Tesla discharging while plugged in to a 100-foot extension cord strikes me as suspect. It's anecdotal at best. Have a look at the Tesla Roadster "Charging" page: http://www.teslamotors.com/goelectric/charging Using 120V @ 15A, you get a charge rate of +5 miles (of range) per hour. Obviously not the optimal solution, but not a net negative either. Adding a 100 foot extension cord isn't going to dimi…

120v @ 15A is 1800 watts. As I said, I was able to measure the wattage being delivered at the end of my 100 foot 16 gauge "home depot" orange extension cord connected to a space heater and found less than 900 watts being delivered to a load that normally pulls 1750. The voltage had also dropped below 100 volts. Its possible that the Tesla simply won't charge at all if the current or voltage on the line becomes too lo…

That's because a 16 gauge extension cord isn't supposed to supply 120v @ 15A. A 16 gauge cord is only good for around 10 amps.

Which means you have a point. If the owner in question plugged the Tesla supplied 120v cord in to an additional 100-foot, 16 gauge cord, they might have a net loss situation on their hands.

Re: "It's A Brick" - Tesla Motors' Devastating Design Problem

#36

Post by D_Alex »

noonespecial wrote: post #26
bradleyland wrote: post #15

Earlier quoted context omitted.

The account of the Tesla discharging while plugged in to a 100-foot extension cord strikes me as suspect. It's anecdotal at best. Have a look at the Tesla Roadster "Charging" page: http://www.teslamotors.com/goelectric/charging Using 120V @ 15A, you get a charge rate of +5 miles (of range) per hour. Obviously not the optimal solution, but not a net negative either. Adding a 100 foot extension cord isn't going to dimi…

120v @ 15A is 1800 watts. As I said, I was able to measure the wattage being delivered at the end of my 100 foot 16 gauge "home depot" orange extension cord connected to a space heater and found less than 900 watts being delivered to a load that normally pulls 1750. The voltage had also dropped below 100 volts. Its possible that the Tesla simply won't charge at all if the current or voltage on the line becomes too lo…

Er, no, this is probably wrong. The voltage drop is due to resistive losses in the long (and skinny) cable, and the resistive losses depend on current flowing. So, unless there are some weird effects due to the car's electronics, you cannot stop the charging, only slow it down.

Re: "It's A Brick" - Tesla Motors' Devastating Design Problem

#37

Post by tibbon »

[deleted] wrote: post #20

[deleted]

I should be able to calculate this... but what's the resistance of that cord then? That's quite a voltage drop.

EDIT: Wow, apparently this is pretty typical and expected as per this calculator: http://www.csgnetwork.com/voltagedropcalc.html

Re: "It's A Brick" - Tesla Motors' Devastating Design Problem

#38

Post by jlarocco »

mcot2 wrote: post #18

I'm much more in favor of hundreds of millions of govt money going towards 50-100MPG+ electric/gas hybrids than all electric at this point. Limited range, hard to "refuel", and now the very real possibility of bricking. I think we are still a long long ways away from practical all electrics.

I'd prefer the government stay out of it all together. Producing vehicles isn't what the government is for.

Second, using a 2500 pound car to transport a 150 pound person 15-20 miles to work every day is incredibly inefficient any way you look at it. If the government is going to be involved at all, it should be to promote walking, cycling, and public transportation. Researching more efficient cars is like trying to replace arsenic in drinking water with mercury - maybe it's not as bad, but it's still bad.

Third, if people were serious about saving the environment and reducing pollution then they'd start living closer to the places they need to go, and stop driving so much altogether. They're not doing that, so I don't think the interest is there.

Re: "It's A Brick" - Tesla Motors' Devastating Design Problem

#39

Post by Aloha »

I would point out that both the Model S and X may very well have the circuitry to completely disconnect the cell pack at something below 10% actual charge (not displayed charge). I'm also really wondering how much of this is self discharge, and how much of this is poor load control of the standby electronics.

Re: "It's A Brick" - Tesla Motors' Devastating Design Problem

#40

Post by jamesaguilar »

rapind wrote: post #14
jamesaguilar wrote: post #2

It seems like it's an inherent in this sort of battery. I'm not sure what Tesla could do to offset this. Computer makers mostly don't offer warranties in the case of negligence or intentional damage. The same seems to apply here.

We're much more accepting of computer and software bugs than vehicle bugs. This, if true, will turn into a PR nightmare for them very fast.

It's a bug in the same sense that internal combustion engines will begin to have problems if their motor oil is not changed. It's inherent to this kind of battery.
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