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Low Amperage Charging

Discussion in 'Model S: Battery & Charging' started by Brightonuk, Apr 30, 2014.

  1. Brightonuk

    Brightonuk Member

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    Is there any advantages to charging at a lower amperage?

    I plug in twice a day at work then when I get home as I don't need much to get me back to my set 75%
    I have been limiting my amperage to 20amps on both locations.
    When charging at home overnight I can go lower and still hit my target charge.
    But am I helping the battery longevity by doing this?
     
  2. SeminoleFSU

    SeminoleFSU Member

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    From what I've read on here, charging at lower amps really won't have any noticeable impact on battery degradation. It does however, lower efficiency in terms of charging loss... So charging at the highest amps possible uses less juice overall, which also means faster charge times resulting in the stations being available quicker for others if needed . Just my $.02
     
  3. Brightonuk

    Brightonuk Member

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    Yes this was just for home and work now I I just read over at Model S Delivery:

    Information shared at the Tesla May 2013 Tech Talks, as reported in this thread:
    • Charging at 40 amps is optimum (implication being don’t trickle charge!)

    Guess I need to amp up
     
  4. DennisLevitt

    DennisLevitt Member

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    Charging at 40 amps seems strange to me. About 8 months ago, before the update to improve vampire creep, I was going away for a couple months. Beyond the mental implications of being away from my Model S for two months (Yes, separation was difficult), I was curious about the best way to leave the car. Tesla Tech Support suggested I leave the car plugged in, but set charging to 10 amps because that was optimum. ????
     
  5. kendallpb

    kendallpb Model S: P 8061

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    Maybe they didn't mean "optimum for charge loss"? It makes sense to me that a recommendation for away-for-2-months, versus a general daily-charging recommendation, may be different. (Vampire losses even back then were not huge; I remember reading it was low enough that people's cars only topped off every 2 days or so.)

    You've given me something to think about, though. I have a trip later this year and hadn't even thought about lowering the charge rate for that. Hmm. Maybe safer (less risk of something overheating) if I lower the charge rate....
     
  6. caddieo

    caddieo Member

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    I'm on my third trip of 4 weeks or more away from my MS (tough to get used to - probably never will) and each time I've lowered the SOC limit to about 140-150 miles at 10 or 12 amps. It has worked well for me so far. On checking with my iPad app, the car has only to make up about 8-12 miles before each charging period (set for 12:30 AM). I see no need to ram the refill in with 40 amps and agree with kendallpb about reducing the risk of overheating.
     
  7. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    If you're even only mildly curious about the technical innards of the battery and how to prolong their life, I'd recommend taking the 75 minutes to watch this video:
    Why do Li-ion Batteries die? And how to improve the situation?

    During the presentation, the speaker addresses the reasons that Li-Ion batteries end up dying. You may be a bit surprised. And you'll also see why Tesla has done some serious kick-ass work in this space.

    If you're not inclined to watch the video - they present data that shows that longer charging cycles at higher temperatures are more damaging than shorter, higher-current charging cycles at the same temperature. You can feel confident charging at 80A, it's well within the battery charge specs and it's actually more efficient on the Model S (according to Tesla's web site). Of course, the battery sitting at high and low SOC's also contributes. I learned a lot from that video.
     
  8. slipdrive

    slipdrive Member

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    Prof. Dahn's research group are the Li-i rock stars. TMC hired a graduate or two a while back. This is defintely where the credibility is.
    I've watched it a couple of times,and still trying to condense the content for my simple mind.

    I just keep:
    * Minimize time at high SOC, especially at temps greater than 75F
    -Be gentle on power at very low SOC
    -Go to near zero once in a while

    maybe in that order.

    Interesting... believe somewhere in there he mentions the cells prefer to be "charged at about the discharge average rate" or something like that. That would seem to me to be about 30-40kW,… but would involve time average mph in the equation which I don't think the car calculates(?)
     

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