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Charging Habits (frequency,120v vs. 240v, etc.) and Impact on Battery Degradation

Discussion in 'Model S: Battery & Charging' started by onlinespending, Jun 24, 2012.

  1. onlinespending

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    Since I rent a condo and don't have my own garage with the ability to easily charge my Model S every night, I'm curious what impact different charging habits may have on the Model S's battery life. Here's a list of possibilities.

    A.) I only charge it every few days (1x - 2x a week) since my commute is short, and do so by charging at public charge stations, friends' houses, work (if they were to have a charge station), etc. If I have the 300 mile range Model S and my commute is just 20 miles round trip, I could easily get by with infrequent charging, but at what cost to the battery life?
    B.) I get access to an electrical outlet in my complex but it's only 120V. I charge it every night via 120V, and am OK with not always being at full capacity because my commute is short. If I am planning a longer trip, I would need to plan accordingly and let it charge longer

    So long story short, what impact on battery life would it have if I were to charge the battery infrequently (only 1x - 2x a week as an example), charge it primarily with just a 120V standard outlet, or a combination of the two? Keep in mind that I may also rarely have it fully charged since I wouldn't have the luxury to charge it overnight, every night at 240V.
     
  2. SCW-Greg

    SCW-Greg Active Member

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    Okay this may answer parts of your question, and probably more than you want to know in other aspects, but it makes for a great knowledge base on battery care and maximizing longevity. From the source...

    Tesla Roadster Battery Care
     
  3. onlinespending

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    Thanks. So based on that thread, it would seem to be beneficial to not always keep it at full charge, which is a problem I certainly won't have. Lets say my commute requires 10% of the battery, I could drive it for more than a week and bring it down to say 20 - 30% SOC before charging it back up. Not only does this fit my living situation well, it actually has the benefit of preserving the battery life a little better.

    I'm still curious about the impact of using 120V as the primary source of charge.
     
  4. Yggdrasill

    Yggdrasill Active Member

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    If you live some place with temperatures outside of the 0-30C range, one thing to keep in mind is that the battery will drain to keep the battery at the right temperature. It won't brick, but to avoid bricking, if the SOC drops below a certain level, the thermal management system will switch off. This isn't good for the battery, as Nissan Leaf users are experiencing at the moment.

    I would go with 120V.
     
  5. Yggdrasill

    Yggdrasill Active Member

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    Also, charging at lower power is better than charging at higher power. I assume the public charging stations will have higher power than the 120V outlet, so again, I would pick the 120V outlet.
     
  6. drees

    drees Active Member

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    Unless you are charging at charge rates of C/2 or higher, charge rates probably aren't going to have a noticeable effect on battery calendar life.

    By C/2 - this means battery capacity / 2 - so for a 85 kWh pack this would be a charge rate of over 40 kW - not going to happen on 240V.

    In contrast, if you only have a standard 120V/15A outlet, you can only charge at 120V/12A max which is 1.4 kW. Hopefully you have a 20A outlet so you can charage at 120V/16A = 1.9kW.

    Now on 240V - it's going to be rare that you have access to more than 240V/40A = 9.6 kW - which is well under the C/2 charge rate of any Model S battery pack.

    IMO the bigger issue will likely be the reduction in charge efficiency when charging on 120V - if it's anything like the Roadster you will lose a lot more energy to heat when charging on 120V. Tom Saxton found that you lose about 40% efficiency on the Roadster charging at 120V/12A compared to 240V/24A, for example. So hopefully Tesla has improved this for the Model S, but I personally wouldn't be surprised if they didn't focus that much on efficiency below 240V/16A charge rates...
     
  7. dsm363

    dsm363 Roadster + Sig Model S

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    onlinespending: Would your condo let you upgrade that connection if you paid for it yourself? You can explain to them how much electricity you'll be using and show them that it really won't make a dent in electricity usage. Tesla recommenders keeping it plugged in when not driving so I'd at least go the 120V outlet route. Maybe you can upgrade it to a 20A outlet at least as drees said. With your short commute, you can still probably top off each night with a 120V outlet since you'll get about 3 miles of range an hour of charging.
     
  8. onlinespending

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    Thanks for the replies. Those two scenarios are more hypotheticals than anything else. It's not as if I have a choice of one or the other. It could be the case that I don't have even access to any kind of electrical outlet where I live (that's in flux since I do seem to move a lot; but do prefer to live in a condo in a city), and would need to find a way to charge via public charging stations, a friend's house, etc.

    dsm363, while it's certainly easier (and therefore recommended out of convenience) to re-charge every night, it would seem that it's actually beneficial to allow the charge to drop a bit before re-charging (say to 50% SOC at least). But when you do re-charge, you'd want to re-charge completely so as to re-balance the batteries.
     
  9. cinergi

    cinergi Active Member

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    Personally, I'd plug it in every night. There's no harm in bringing it to full (in standard mode) if you're using it every day. The Roadster is significantly more efficient when charging at 220/40A so if the Model S is similar, it may cost you less in the long run to get a 220 connection. Plus of course it's faster to charge.
     
  10. Frankrb

    Frankrb Member

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    Will ask a slightly different question re MS charging. I plug in everyday when home, and am generating my own solar power. I have both 110v/12A and 240v/40A in my garage. Most of the time, I can charge using simple 110/12a, because I can max out to normal charge (getting 275-278m ideal indicated) before my next ride, and my gut tells me charging at 110v (normal or warm temps) is easier on the battery than 240v. Trying to do the best for long term battery life. Is this reasonable and true, or is it basically inconsequential? Any references and/or advice will be much appreciated.
     
  11. dsm363

    dsm363 Roadster + Sig Model S

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    It may be less efficient to charge at 110V/12A than at 240V 40A. Charging at 40A shouldn't harm your battery just do a standard charge and start charging so it finishes about an hour before you take off in the morning.
     

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