5 ms·

Could this really not be prevented by a $10 microcontroller and a big-ass relay to just disconnect the battery if it reaches a certain discharge state? Even my

Could this really not be prevented by a $10 microcontroller and a big-ass relay to just disconnect the battery if it reaches a certain discharge state? Even my iPhone can turn turtle to protect its battery when it gets too low. Also how much power does it take to keep the damn thing plugged in? The article indicates that a 100 foot extension cord isn't enough just to break even and the car discharges even when plugged in. A 100 foot cord of cheap 16 gauge wire can still supply almost 900 watts before the voltage drops below 100v. So it uses a kilowatt just to stand-by without even charging? That's one hell of a power vampire. I think maybe they should spend a bit more time on the fundamentals and a bit less time on fancy bird-wing doors if they want to have a real product. The real car of the future is just a big dumb tray full of indestructible nickle-iron batteries and 4 wheel-hub motors bolted to the corners.

bradleyland 15y ago
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 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 diminish the available current enough to result in a net negative, so either the owner had additional electrical issues, or simply failed to plug it in and is making up excuses.
- nash 15y ago
  I would agree. The whole document has a few little niggles that make me think it's BS, or at least severely overblown. Additionally they quote it's happened 5 times... by an un-named service manager.
  - geori 15y ago
    Totally Agree. There are no names, only anecdotes and the science is suspect. This article is 100% B.S. and I wouldn't be surprised if it was planted by a competitor.
    - david927 15y ago
      The bigger an industry is, the harder they fight for their existence. Elon Musk is not just taking on the second biggest industry, the auto industry. He's also taking on the biggest industry: oil. It looks like they switched from ignore/mock to attack. He's getting somewhere. First they ignore you, then they laugh at you, then they fight you, then you win. --Gandhi
- noonespecial 15y ago
  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 low. In this case, it would be "plugged in" but not charging. Edit: Lets figure it out: Range=244mi. Battery capacity=58kWh. So: 5 miles takes 1.086kWh. 10% is lost in chemical conversion so we really need 1.207kWh for those miles. We pull at a rate of 1.8kWh/h from the plug. So 600 watts or so is lost elsewhere. We know the "always on" battery cooling system alone takes around 150 watts. Its not that far fetched. Edit: I deleted my comment below where I calculated the cost of keeping the car on standby because I don't think I made clear enough (and didn't want to type it all twice) the difference between the actual discharge rate of the battery and the amount of power required at the charger to stop it. It just seems to take a lot of power at the charge port before any gets to the battery. The battery seems to discharge at an average rate of just 30 watts, but it seems to take a much, much greater amount of power input to prevent this and failing to provide this power has dire consequences. Why?
  - jws 15y ago
    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.
URSpider94 15y ago
Could this really not be prevented by a $10 microcontroller and a big-ass relay to just disconnect the battery if it reaches a certain discharge state? Not necessarily. This might help, but the battery will also have self-discharge, meaning that it can lose charge without being connected to any load at all. If you get the charge down low enough, and then wait long enough, then even a full disconnect from the system won't help.
- wisty 15y ago
  You could add a $100 mobile phone, which auto-calls a service center. If 1% of cars get "bricked", that's $10,000 per car saved, not including intervention costs. Even with some false positives, it would be worth it. Of course, that cost is carried by Tesla, not the customer. "The Tesla manager called me to warn that my car was in trouble" is a much better customer experience than "my Tesla broke down, and cost $40k to fix". Cars used to have the same problems with oil changes. This got better, as customers were educated (at the cost of a lot of cooked engines), and cars were able to warn their owners, and run for longer without oil.
  - bri3d 15y ago
    That's exactly what Tesla do, even once having gone so far as tracking the car down via GPS and charging it themselves when the owner was unresponsive.
    - thebooktocome 15y ago
      Certainly that's going to peg some people's creepy meters.
      - toomuchtodo 15y ago
        As a Model S reservation holder, it pegs my pocketbook meter. If I'm about to lose $40K on my car because of a battery, I have no problem with them showing up in my driveway to charge the vehicle if necessary. Creepy? I'm more worried about the app-of-the-day sucking down my iPhone contacts. THAT I find to be more personal than my vehicle location.
CamperBob 15y ago
Perhaps the most straightforward fix would be to simply refrain from drawing any current at all from the vehicle's main battery while parked. The alarm and any other standby processes should run from a 12-volt motorcycle battery or something, which is recharged during driving, and can be jumped like any other car battery if allowed to go dead. That wouldn't fix the Li-ion self-discharge problem completely, but it could provide as much as a few months' worth of margin. In any case it's batshit insane to leave early adopters stuck with a $40,000 bill for your lack of engineering foresight. That was the real surprise in the article.

bradleyland 15y ago

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 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 diminish the available current enough to result in a net negative, so either the owner had additional electrical issues, or simply failed to plug it in and is making up excuses.

nash 15y ago
I would agree. The whole document has a few little niggles that make me think it's BS, or at least severely overblown. Additionally they quote it's happened 5 times... by an un-named service manager.
- geori 15y ago
  Totally Agree. There are no names, only anecdotes and the science is suspect. This article is 100% B.S. and I wouldn't be surprised if it was planted by a competitor.
  - david927 15y ago
    The bigger an industry is, the harder they fight for their existence. Elon Musk is not just taking on the second biggest industry, the auto industry. He's also taking on the biggest industry: oil. It looks like they switched from ignore/mock to attack. He's getting somewhere. First they ignore you, then they laugh at you, then they fight you, then you win. --Gandhi
noonespecial 15y ago
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 low. In this case, it would be "plugged in" but not charging. Edit: Lets figure it out: Range=244mi. Battery capacity=58kWh. So: 5 miles takes 1.086kWh. 10% is lost in chemical conversion so we really need 1.207kWh for those miles. We pull at a rate of 1.8kWh/h from the plug. So 600 watts or so is lost elsewhere. We know the "always on" battery cooling system alone takes around 150 watts. Its not that far fetched. Edit: I deleted my comment below where I calculated the cost of keeping the car on standby because I don't think I made clear enough (and didn't want to type it all twice) the difference between the actual discharge rate of the battery and the amount of power required at the charger to stop it. It just seems to take a lot of power at the charge port before any gets to the battery. The battery seems to discharge at an average rate of just 30 watts, but it seems to take a much, much greater amount of power input to prevent this and failing to provide this power has dire consequences. Why?
- jws 15y ago
  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.

URSpider94 15y ago

Could this really not be prevented by a $10 microcontroller and a big-ass relay to just disconnect the battery if it reaches a certain discharge state? Not necessarily. This might help, but the battery will also have self-discharge, meaning that it can lose charge without being connected to any load at all. If you get the charge down low enough, and then wait long enough, then even a full disconnect from the system won't help.

wisty 15y ago
You could add a $100 mobile phone, which auto-calls a service center. If 1% of cars get "bricked", that's $10,000 per car saved, not including intervention costs. Even with some false positives, it would be worth it. Of course, that cost is carried by Tesla, not the customer. "The Tesla manager called me to warn that my car was in trouble" is a much better customer experience than "my Tesla broke down, and cost $40k to fix". Cars used to have the same problems with oil changes. This got better, as customers were educated (at the cost of a lot of cooked engines), and cars were able to warn their owners, and run for longer without oil.
- bri3d 15y ago
  That's exactly what Tesla do, even once having gone so far as tracking the car down via GPS and charging it themselves when the owner was unresponsive.
  - thebooktocome 15y ago
    Certainly that's going to peg some people's creepy meters.
    - toomuchtodo 15y ago
      As a Model S reservation holder, it pegs my pocketbook meter. If I'm about to lose $40K on my car because of a battery, I have no problem with them showing up in my driveway to charge the vehicle if necessary. Creepy? I'm more worried about the app-of-the-day sucking down my iPhone contacts. THAT I find to be more personal than my vehicle location.

CamperBob 15y ago

Perhaps the most straightforward fix would be to simply refrain from drawing any current at all from the vehicle's main battery while parked. The alarm and any other standby processes should run from a 12-volt motorcycle battery or something, which is recharged during driving, and can be jumped like any other car battery if allowed to go dead. That wouldn't fix the Li-ion self-discharge problem completely, but it could provide as much as a few months' worth of margin. In any case it's batshit insane to leave early adopters stuck with a $40,000 bill for your lack of engineering foresight. That was the real surprise in the article.