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Charging time

Discussion in 'Roadster' started by WarpedOne, Oct 2, 2006.

  1. WarpedOne

    WarpedOne Supreme Premier

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    Has anyone caught any info about how much is 3,5 hours full charging time mandated by battery tech and how much by tipical electrical outlet power?
    If a power outlet capable of delivering say 200A at 220V was availabe would charging time decrease (and how much) or not (because of battery limitations)?

    My GSM takes about an hour for a complete refill. Why would 6800 GSM took any longer? If required power was available of course.
     
  2. electrified

    electrified Member

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    You are probably right. However, larger currents would require 3 phase power, which in turn would require an industrial power installation. You could not do that at home. However, a commercial recharging station might. If electric cars take off, I would expect to see charging stations in parking lots, particularly near interstates and simular highways. Some of these could be 3 phase. Tesla could adapt the car for 3 phase because the motor runs 3 phase. I suppose some reading this don't understand 3 phase electricity, but it alows better use of wires. The comercial grid is 3 phase.
     
  3. WarpedOne

    WarpedOne Supreme Premier

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    I was thinking in line of CCS (Commercial Charge Stations) with powerful connections, yes.
    50kW CCS could fill you up in about an hour. That would give you just enough time for lunch. :)
    If batteries would allow that, of course.
     
  4. WarpedOne

    WarpedOne Supreme Premier

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    Tesla is using 17kW charger unit, that is capable of recharging it in 3,5 hours.

    This paper: http://www.acpropulsion.com/PDF%20files/Level_2_plus_EVS17.pdf#search=%22SAE%201772%20AC%22 makes me believe charging time is limited by charger unit and not batteries alone. With higher power charger (and connection) a charging time could be reduced, but you couldn't do that at home. Not many homes have such powerful electric connections.

    What is needed is higher power charging standard, so charging stations could be established offering fast charge service. Of course, some premium would be paid for luxury of fast charging and you could still afterall charge at home at night at low costs.
     
  5. iisjsmith

    iisjsmith Member

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    If I remember correctly most batteries have a maximum level they can be charged at.

    For instance, the Kokam SLB 452128 lithium rechargeable battery has a maximum charge current of 1C. Since the capacity of this battery is 145mAh they spec 1C as being 130mA. For reference the max discharge current of these batteries is 260mA, or 2C.

    So most batteries are limited to what current can be supplied during recharge, but I have seen Li-Po batteries with high charge currents. For instance, the A123Systems new nanoparticle Li-Po batteries are rated at 2300mAh and can endure a 10A charge current. They can also discharge at 120A for a 10 second discharge!!
     
  6. WarpedOne

    WarpedOne Supreme Premier

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    You are correct, batteries have their internal limitations that in effect constrain minimum posible charging time.

    What I am suggesting here is that minimum charging time for current Tesla's batteries is NOT 3,5 hours but considerably less, same as your standard cellphone with LiIon battery - about 1 hour. A quick calculation tells us that putting 50kWh of energy into any battery in one hour requires at least 50kW of electrical power. Charging gear would have to channel 500Amps at 110V or 250Amps at 220V. This is some SERIOUSLY STRONG electric current and quite hazardous to fiddle with at your home. So, Tesla took a safe path and used most powerful home charging standard in existance. It is spec'ed at 17kW and provides for full charge in 3,5 hours.

    With this same 17kW charger and same home electrical installations no new miraclous battery technology can considerably shorten charching time. More powerfull charging standards and more powerful home electrical installations that are required for that are both very unlikely to come into existance anytime soon.

    I expect when batteries that are capable of storing more energy come into usage, charging time will even LENGTHEN. Putting 100kWh of energy into the batteries will require about 7 hours of charging. But they will also give you at least 500 miles of range. The best solution is to simply accept this charing time as an inherent feature of electric car and adopt to it. If you charge your electric car every night it suddenly becomes a no-issue. Every morning the batteries are fully charged and you have waited for exactly ZERO MINUTES.
     
  7. iisjsmith

    iisjsmith Member

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    >> What I am suggesting here is that minimum charging time for current Tesla's batteries is NOT 3,5 hours but considerably less, same as your standard cellphone with LiIon battery - about 1 hour.

    We can't know this without knowing the maximum charge current for the cells that make up the Roadster ESS. For all we know that 3.5 hour number could be the absolute maximum. We need some more info on what type of cell they used.

    Hopefully as cell capacity increases there will be a matching increase in both discharge and charge current maximums. So that as capacity increases we will not see a increase in charging time, like you suggest. But it is possible that cell designers could put more research into expanding capacity, thinking that is what consumers want, rather than charging times.
     
  8. WarpedOne

    WarpedOne Supreme Premier

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    >> We can't know this without knowing the maximum charge current for the cells that make up the Roadster ESS.

    Ok, I agree. We can't be 100% sure into 1hour charing capability of current Tesla batteries. I am pointg out that there are already mass-produced LiIon batteris that are capable of 1hour charging time. Almost everybody has them in their cellphones. Tesla probably could use them if they choose so. So no new battery technology is needed to reach that 1h charging time, only more powerful charging standard and installation.

    TM could probably use (cheaper?) batteries, that take longer to charge, because of its 17kW charger limiation. Fast charging would go unused.
     
  9. iisjsmith

    iisjsmith Member

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    Yea, that 1 hour time is pretty easy to hit with current batteries. I have seen plenty of li-ion cells with 1C charging current limits.

    I think what you are likely to see in regards to a charging station is large flywheel or capacitor arrays stored underground...just like the large fuel tanks are stored now. These would be kept charged from the grid. You could pull up, plug into a line, and get a fast blast of charge into your pack.

    Active Power (http://www.activepower.com) have a CleanSourceDC flywheel product (CSDC-500) that stores 500kW and has a maximum rated output power of up to 550VDC. They can be linked in parallel into 2000kW arrays!! That's enough to charge 40 Roadsters.

    Like you said, the battery tech is already there. We just need the stations! ;)
     
  10. iisjsmith

    iisjsmith Member

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    For some more information on the Active Power flywheel systems, I was also looking at their CS2 product:

    CS2-500 is a dual flywheel system that delivers 500 kW to the DC bus at 480 VDC
    - system footprint = 42”w x 34”d x 78”h
    - output = CS2-500 delivers 500 kW to the DC bus.
    - voltage range =360 VDC to 550 VDC. The voltage level remains constant during discharge at a preset level.
    - maximum current output = 1042 Amps for approximately 15 seconds. The Voltage level remains constant.
    - minimum current draw during recharge = as little as 15 amps per flywheel.
    - optimum current draw during recharge = 105 Amps per flywheel.
    - full recharge time = fully recharged after at full discharge in less than 2.5 minutes.
    - short recharge time = little RPM is lost during short discharge and recharge is complete in a few seconds.
    - input voltages = 120, 230, and 480VAC at 50 or 60HZ. 480VAC 60HZ is standard.
    - life expectancy = 20 years.
    - link options = up to 4 units can be daisy chained in parallel for up to 2000 kW.

    Combine this with li-ion or li-poly cells with 2C to 5C charge currents, and you are down into minutes for full pack recharge.
     
  11. WarpedOne

    WarpedOne Supreme Premier

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    >> and you are down into minutes for full pack recharge.

    Hmmm, 100kWh at 480VDC in 10 minutes gives you 1255Amps of electric current. People with pacemakers would love to stand near :)
    This charging stations are probably doable, but would certainly come at hefty price tag. Your home electricity would probably cost you several times less.
     
  12. tsla

    tsla New Member

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    There is one thing you have to keep in mind. Yes, you can recharge your cell phone battery in 1 hour; you will also realize that the battery gets warm during the charging process. Shorter recharging time means higher charging current and warmer battery. The main problem-cause here is the internal series resistance of the battery cell. These batteries have series resistance (in the range of 70mOhms). This means that during charging or discharging there will be some loss of energy that will be felt as heat. Like anything else these batteries have maximum operating temperature which if exceeded can lead into battery damage or complete battery destruction (battery explosion). Again, the reason you can charge a cell phone battery in 1 hour is that a single battery can be cooled down easily while Tesla Motors’ 6831 battery cells tightly packed can not be cooled down that fast so the temperature has to be limited and controlled. There is a direct relation between the battery temperature (excluding ambient temperature) and the battery current.
    Supper Capacitors operate at different principles from the batteries. Super Capacitors have internal series resistance much smaller than batteries therefore they can be charged with proportionally higher currents and as a result proportionally shorter recharging time. But, then there is still old problem with home power outlet not being able to provide enough power (someone mentioned earlier it is 17kW). So it looks like fast recharging will be done at specialized rapid charging stations (like today’s gas stations).
     
  13. Takumi

    Takumi Member

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    I may have missed it, but does the charger have a built-in automatic timer? What I mean is that it allows you to set it so that it starts charging during off-peak hours or any other time you want it to? If it does, does it have a "start charging now" bypass button as well?
     
  14. WarpedOne

    WarpedOne Supreme Premier

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    Yes, it does. You can also set at which level to stop charging to conserve the batteries.
     
  15. TEG

    TEG TMC Moderator

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    #15 TEG, Aug 18, 2007
    Last edited: Aug 19, 2007
    Once nice feature of the Roadster is that it has a lighted ring in the charging socket. You can see some details of level of charge simply by looking at the color being emitted around the charger plug.
    [​IMG][​IMG]

    I haven't seen that feature on any other EVs.
     
  16. mherzfeld

    mherzfeld Member

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    #16 mherzfeld, Aug 18, 2007
    Last edited: Aug 18, 2007
    Charging connection specifications

    Would like to get the specifications of the wiring requirements on the load and line side of the charger for a typical residential installation (RCS) and for the commercial charging station (CCS). What is are the wiring specifications so electricians can easily wiring the charging station in a residential application?

    Has anyone installed a residential service connection charging station (RCS) with these specifications? When an automobile is purchase would it be a good to provide the specifications of how connect to a 200A residential service? Breaker at more than 70 amps wires be sized larger than ... ?

    How would the installation be configured if there was also a solar electric system installed?
     
  17. TEG

    TEG TMC Moderator

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    I don't think the charger wiring has any dependency on any grid-connected solar systems that may be installed. Those are handled on a separate breaker, and don't change anything about the way the charging system works.

    My (non Tesla) 6kWh EV charger is connected to a typical split phase 240v "dryer" type circuit with two 30amp breakers. If such a circuit has a NEMA 13-50 socket, you could use one of the Roadster's charging adapters to plug in and recharge in roughly 8 hours. (e.g.: overnight off of a 240v dryer outlet).

    I don't know the particulars of the 3.5 hour charger, but I would think you would need two 80amp breakers or something like that. Perhaps Roadster customers who opt for the higher current home charging station will get some paperwork that will explain the particulars to an electrician doing the installation.

    The most complicated part may be permits...
     
  18. tonybelding

    tonybelding Active Member

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    I hope the chargers are delivered early enough -- ahead of the car -- to give us time to get that sorted out. It takes a long time to get anything done where I live.
     
  19. mherzfeld

    mherzfeld Member

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    Charging connection specifications

    With a 6kW charger would be at about at 25 amps which about 30 amp breaker which appears to be about right. However at 17kW would be at about 70 amps ... In addition, for residential solar electric systems the backfed breaker can be 120% and for commercial would be 100%. There is a issue whether there the solar system and or charger should be on the load or line side of the service with adequate overcurrent protection.
     

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