Tesla cars allowing batteries to become fully discharged?

[bobbagum]

Not sure whether to post this in battery forum or here, since the car uses 18650s...

http://jalopnik.com/5887265/tesla-mo...design-problem

After reading this article, I'm curious, what were the engineers prioritizing in designing such circuit that would allow batteries to be discharged with no safety cutoff, I mean it's a car, there's plenty of room, I've never used a phone or laptop computers that would allow itself to discharge lithium batteries to the point of damage.... anyone care to speculate?

[SHADE02]

woOW, I just read the entire article, man... 40k USD for a new spare batterie,,, thats sucks


and terrible CS from tesla too...
and yes , why in the name of hell, they, just simply no put some baterie volts cut-off or something??????!!

[TEEJ]

Probably were more worried about maximizing range, and the minimizing the rage a customer would feel towards them if the battery had enough juice to get them to that next outlet, but just refused to drive a little further, etc.

It DOES seem short sighted to not include some sort of safety net though, perhaps a setting to cut the parasitic drain at least to avoid continued discharges?

[bobbagum]

would the protection circuit still drain the battery even after it has dropped enough to trip the cutoff? I'm talking for normal 'protected' cells that we normally use here....

btw the roadster uses 6831 18650s, if someone were to buy a replacement for all that with say... AW's cells, that would be.... ouch

[RBR]

Not sure whether to post this in battery forum or here, since the car uses 18650s...

http://jalopnik.com/5887265/tesla-mo...design-problem

After reading this article, I'm curious, what were the engineers prioritizing in designing such circuit that would allow batteries to be discharged with no safety cutoff, I mean it's a car, there's plenty of room, I've never used a phone or laptop computers that would allow itself to discharge lithium batteries to the point of damage.... anyone care to speculate?

Hahaha, now that´s a pretty fine example for planned obsolescence.



Cheers

RBR

[ssvqwnp]

It seems to me they should just give the cars primaries and make the whole thing disposable... The article makes it appear that's what'll happen with the Model S with it's lower price tag and proposed more expensive battery(s).


[Also, for those that didn't catch it, the first sentence was sarcastic. You know who you are.]

[fnsooner]

Tesla was afraid they would get sued by Surefire if they installed a lockout tailcap.

[yellow]

its the problem with ppl doing something but have not full understanding of everything.
They probably have a hell of a designer,
technicials/electricians for normal cars, used to lead batteries, ...

[uk_caver]

Would this still happen even if the battery was entirely disconnected from the car?

It's not clear what a car needs to use meaningful power for when it's unoccupied.

Are there no consumer-protection laws which would support someone with a bricked car taking action against a manufacturer who seemed to have made some pretty poor design decisions, and who had limited the severity of warnings for the sake of not putting customers off the vehicles.

[CKOD]

it loses 50% of its charge in 1 week? with a 50+ KWh battery pack, thats ~150 watts of load constant. Thats definitely not energy star compliant I wonder what they are running, battery heater etc? maybe understandable in a cold climate, but not a temperate one. Also shame on them if they cant manage to eek out 150W to maintain the car over a 100' extension cord, thats only 2A or so after charger inefficiencies.

[uk_caver]

Shame on them if a charger (whether plugged into a long extension lead or not) doesn't indicate when it is and when it isn't supplying meaningful current.

[uk_caver]

Also shame on them if they cant manage to eek out 150W to maintain the car over a 100' extension cord, thats only 2A or so after charger inefficiencies.

Even if they were pulling 10A through a 10A rated cable (~1mm2), that's only something like an ohm in total (both ways) for 100ft, losing 10V.

[Sub_Umbra]

The main issue of this thread is moot as modern electric cars aren't going anywhere (with the possible exception of up to the 7-11 for some Ben and Jerry's for Ed Bagley Jr)

-- We don't have the GRIDs it would take to charge all of those electric cars. Especially the 'pie in the sky' hype about the ones that pick up a full charge in two hours. OK, so scores of millions all drive their little cars home and plug them in at 6p. Our grids can not cope with a hot day AND NO ELECTRIC CARS all plugging in at the same time.

-- We don't even have a plan to change our grids to be able to handle it at some vague, nebulous time in the future. (That is really a bad sign in Western culture where we're pretty much willing to lie about nearly anything in the future if it will make us a few bucks in the now.)

-- The batteries are expensive, fragile, short-lived and like the steam car in
"The Carpetbaggers" they are not anything that most want to have anywhere near them in a car accident.

-- All 'Rare Earth' minerals come from China. This will not change in the next ten years. Rare Earth minerals are very important to schemes like this. Without Rare Earth minerals your iPod would weigh three pounds. Rare Earth minerals are not being exported by China the way they have been in the past. Without Rare Earth minerals all of this talk of efficient electric cars is nothing but hucksters pumping venture capital and hoping for inflated IPOs. My point here is that if Westerners decide that they MUST drive electric cars they will, in fact, be made in China into the significant future.

Frankly, I don't even think that Americans are dumb enough to go this route, especially after it is pointed out to them repeatedly that for all of their 'greener than thou' smugness they have somehow figured out how to feel good about electric cars that actually run on coal. Yup, that's right, in the States most electricity comes from coal. And yes, it will have to be pointed out repeatedly.

Hey, what could possibly go wrong? I ax ya?

If I like coal I'm a Luddite, but if I support today's electric cars that run on coal I'm warm, fuzzy, green and adorable.

[hopkins]

The Tesla battery module weighs 900lbs. Its liquid cooled. It has 6,800 18650's inside of it. Each of the cells has it own temperature
sensor and 2 fuses that can be individually triggered to open if a runaway thermal event occurs. There are 12 microprocessors inside the battery
module that are always on. Cannot be turned off.

(who knows how many computers are in the rest of the car?) (Lots)

These 12 microprocessors are always monitoring for unsafe cell conditions and are a constant parasitic drain on the 375volt 53Kw battery.
There is no way to access them as they are embedded in the 900lb battery module.

Without a recharging hookup this battery monitoring system will 'Brick' the car all by itself. Drain all the 18650's.
Current draw seems to be 0.42amps for this safety system.

Probably some nice vampire dc-dc converters to make 5volts
for the 12 microprocessors guaranteed to kill the $40,000 battery module.

[uk_caver]

So presumably the protection circuits are there partly in case of physical damage or thermal runaway of an individual cell when the car is not running, to disconnect internal shorts and try to prevent a chain reaction of failure?

Otherwise it would be possible to turn them off or hibernate them when the car didn't actually need the main battery, and power what few devices actually needed power from a small/cheap battery.

[uk_caver]

-- All 'Rare Earth' minerals come from China. This will not change in the next ten years. Rare Earth minerals are very important to schemes like this. Without Rare Earth minerals your iPod would weigh three pounds. Rare Earth minerals are not being exported by China the way they have been in the past. My point here is that if Westerners decide that they MUST drive electric cars they will, in fact be made in China.

I thought that with rare earths, part of the pont of the supply restriction/internalisation was to encourage other countries to start producing because China expected to be a net importer in the medium/long term.

The more confident people are that prices won''t suddenly drop and pull the rug from under a new venture, the sooner that alternative sources seem likely to get going.

[Sub_Umbra]

I thought that with rare earths, part of the pont of the supply restriction/internalisation was to encourage other countries to start producing because China expected to be a net importer in the medium/long term.

The more confident people are that prices won''t suddenly drop and pull the rug from under a new venture, the sooner that alternative sources seem likely to get going.

It is my understanding that China reached the monopoly they have today by DUMPING Rare Earth minerals. (Dumping in this context would mean the export of said minerals internationally at below their cost of production in an attempt to shut all other mining operations down. It worked -- it will take a minimum of ten years to begin significant returns on mining operations of rare earth minerals begun today.)

"...All your electric cars are belong to us..."

[Wrend]

...

How did this thread get here?

I think you need to crunch some actual numbers more and make generalized assumptions less.

Did you know that you could charge a battery powered electric car with a relatively cheap gas powered generator and still get better gas mileage and pollute less?

The beauty of "going electric" is that it can get its energy from anywhere, and that energy can be used a lot more efficiently.

The only real hindrance is the prohibitive cost of larger battery capacity.

[uk_caver]

It is my understanding that China reached the monopoly they have today by DUMPING Rare Earth minerals. (Dumping in this context would mean the export of said minerals internationally at below their cost of production in an attempt to shut all other mining operations down. It worked -- it will take a minimum of ten years to begin significant returns on mining operations of rare earth minerals begun today.)

Ten years to start meaningful production even in the face of demand and limited supply?

[Sub_Umbra]

How did this thread get here?

I think you need to crunch some actual numbers more and make generalized assumptions less.

Did you know that you could charge a battery powered electric car with a relatively cheap gas powered generator and still get better gas mileage and pollute less?

The beauty of going electric is that it can get its energy from anywhere, and can be used a lot more efficiently.

The only real hindrance is the prohibitive cost of larger battery capacity.

I am not impressed. While you have responded you have not addressed even one single issue I brought up.

You are making my points for me by your lack of any arguments. Perhaps you who have attempted to bring me to task for making, as you said, "...genralized assumptions..." could take a minute and focus your thoughts. It might be handy for you to comment about things I have posted, instead of commenting on things I haven't ever written.

[Sub_Umbra]

Ten years to start meaningful production even in the face of demand and limited supply?

Yup. It turns out that Rare Earth Minerals is a very poor term for minerals that are scattered very thinly throughout the entire world. Searching will turn up a big effort in (I think) Kansas. They are dumping boucoup bucks into this and according to the news reports it will be at least ten years before any significant production is reached.

By all means, look it up and correct me if I've got it wrong.

[Wrend]

...

Please don't mistake my post for a conversational "debate." I'm just offering my point of view, not trying to change your beliefs.

[Sub_Umbra]

No worries there.

[hellokitty[hk]]

AFAIK, the 18650s are A123 LiFe chemistry.

[StarHalo]

It's a toy; people who spend this much on toys have no problem with the ridiculous maintenance budget. And it's essentially half the price of the cheapest Ferrari.

The version I can afford is in Forza 4 for XBox. It's a unique challenge to hustle around the track, since there's no gear to select for each specific turn (and no way to downshift if you blow it), and no engine sound to tell you what the motor is doing..

[jasonck08]

Not only did Tesla forget to install a Low voltage cutoff, they also made a mistake in choosing to use cells rated for ~300 cycles.

The car gets 200 miles max per charge and the cells in the pack are good for 300 cycles tops. So that means that if you exclude the fact that the battery discharges significantly on its own, and you do the math 200x300, that means the car is good for 60K miles max before needing a new battery @ $40K+.

So assuming there is no additional maintenance besides tires and brakes in the first 60K miles, you are still paying likely around ~45K in maintenance for driving 60K miles. Not only that but the fact that it discharges ~25Kwhrs per week. 25Kwhrs is going to cost around the price of a gallon of gas. And thats the price for just storing the vehicle! The only green I see in the tesla is the stack of money you hand over to buy and maintain one of these cars.

[Wrend]

Which cells did they use that only get 300 cycles?

AFAIK, the 18650s are A123 LiFe chemistry.

If this is the case, then more fully discharging, and cycle life shouldn't be much of an issue.

[jayflash]

Electricity was once feared and banned in some places. Getting to the moon was considered folly. It remains possible that affordable, reliable, electrical storage may become available in acceptable size/weight limits. I won't be holding my breath, but, who knows? Plug the car in during off-peak periods and existing AC sources may be sufficient.

Too bad electric cars aren't yet practical because motors are superior to ICE's and the torque at stall would make them a blast to drive.

[AnAppleSnail]

Too bad electric cars aren't yet practical because motors are superior to ICE's and the torque at stall would make them a blast to drive.

It depends on how your motor is built - but of course if you do it right there is potential for great fun. I wouldn't mind a diesel/electric (Well-tuned diesel generator powering motors and/or battery storage) powered car with high-torque hub motors. Trains and tugboats use these for 100% torque at zero rpm to begin moving. With a generator and some buffer power source, it would be delicious to smoothly press the accelerator to the floor and silently (or not) reach speed.

[StarHalo]

the torque at stall would make them a blast to drive.

The Tesla modulates the amount of power you get from a stop as a sort of launch control; you don't get 100% of the motor until roughly 45 mph. Flooring it from a stop, the tires barely chirp, and you can watch the power gauge climb as more power is delivered at more speed, giving you a nicely controlled launch. You can somewhat circumvent it by brake torqueing (depress brake and accelerator, release brake), or drifting/donuting so the motor is already pegged going into a low speed, but if you really want the wall-of-smoke burnout, do it in reverse - the short gearing combined with unmodulated, almost instantaneous 100% power leaves the wheels spinning until ~50 mph..