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Different chargers - different miles

Discussion in 'Roadster' started by Strib, Jun 17, 2015.

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  1. Strib

    Strib Member

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    Yay! I finally finished all the work on the breaker panels and the #4 wiring in the garage over to where I mounted the Roadster High Power Charger (Clipper Creek), and all is well. No longer am I using my 110VAC mobile charger at 15A - I've set my new charger to 56A, 220VAC!

    But... I'm getting about 10 fewer miles range than I was used to! I reverted back to the little 110VAC connector and again get what I was accustomed to. I've repeated this several times with the same results. Topping off doesn't make much difference.

    Anybody else experience this?
     
  2. Stefan T

    Stefan T Member

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    my roadster do somthing in that way to
    if i charge 230V 13A wii i get 294-298 km but with 24A only 291-296 km and the diffrece sems to have with temp out doors and how i have drive the car and the distance i have driven
    or if i charge 10A i will get some more km
     
  3. hcsharp

    hcsharp Active Member

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    Yes, we all experience that. I usually get between 3 and 10 miles more with 120v charging. The same is true but to a lesser extent at 240v. For example, if you charge at 240v 24A you will usually finish with a couple more miles than at 80A.
     
  4. supersnoop

    supersnoop Tesla Roadster #334

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    Charging at a lower voltage creates less heat. That's less energy lost as heat, and less risk to the battery when charging. So, at lower voltages, you'll get a little more juice.
     
  5. hcsharp

    hcsharp Active Member

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    Those things are true, except your conclusion doesn't necessarily follow. The car doesn't stop charging based on how much power was used to charge it.

    My own theory (unverified) is that charging stops when the cells reach a certain voltage, eg. 4.15v for range mode. The charger never goes higher than this voltage. To charge at a higher rate the spread between the charger voltage and the cell voltage has to be greater in order to push more amps. I think that spread might be partially responsible for the difference in miles. In theory it tapers down at the end to help the cells catch up to the charger voltage but it never tapers down as much or as soon when you charge at higher amps.
     
  6. Doug_G

    Doug_G Lead Moderator

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    I agree with hcsharp. Ohms law. For the purpose of this thought experiment, replace the cell with an equivalent resistance. Now try to make more current go through it - you'll find the voltage across the cell is higher. So charging at higher current causes you to hit the stop voltage slightly sooner.

    I expect the taper is a fixed profile; Tesla seems to do everything that way. So it will end up being lower at the end if you start out with less power.
     
  7. m0rph

    m0rph Member

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    #7 m0rph, Jun 18, 2015
    Last edited: Jun 19, 2015
    I also experienced this (10km less on std charge). And I read some theories here, but I'm still not convinced. When I use my 63A charge station and limit it to 10A, it still stops the charge earlier than when I use the standard charger rated 230V 13A.
     
  8. markwj

    markwj Moderator, Asia Pacific

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    Real world equivalent:

    1. Run as fast as you can, then try to stop exactly on a white line across the track. Don't cross the line, but get as close to it as you can.
    2. Now, do the same experiment while walking slowly.

    See which speed gets you closest to the line.
     

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