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Charge on plug-in or delayed charge?

Discussion in 'Roadster' started by asgard, Apr 24, 2016.

  1. asgard

    asgard Member

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    This topic may have been beaten too many times, but I am wondering about charging on plug-in to cool the battery vs. charge when below 60% SOC.
    My trips are about 25-45 miles of freeway driving uphill/downhill and I have been charging at 208V/30A immediately on parking to cool the battery.
    Over the course of a year I have lost about 4-5 miles of standard mode charge capacity, dropping from 191mi to 186mi. This is after my battery was replaced under warranty due to a defective sheet.

    I am wondering if I should just let the car sit and charge only when my SOC drops to 140mi or below, for longevity of the battery.
     
  2. FlatSix911

    FlatSix911 918 Hybrid

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    I always plug in upon arrival home and schedule charging to start at 8PM due to low TOU evening rates.
    Why use energy to cool your battery pack when you can let it cool for free and charge later at lower rates?
     
  3. David99

    David99 Active Member

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    In terms of battery temperature, you don't have to worry. The car doesn't need to be active charging to maintain battery temperature. You don't have to worry about cooling the battery. Tesla does it for you no matter what.

    In terms of degradation over time, it is better to keep the battery at a lower state of charge. So from that perspective, it's better to delay the charge so the battery sits at a lower level for longer.
     
  4. gregd

    gregd Member

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    I asked the same question, and got a few answers. The conclusion seemed to be to not wait, and charge whenever you can, but there wasn't a clear consensus (as you can already tell...).

    I modify that a bit. I get 4hrs of free charging at work, so I charge there. In the winter, everything stays pretty cool, so I just do the round-trip with charging there. If there's going to be a long bit of bad weather, I'll charge it up at home and take the beater car instead. Otherwise, it spends most of its time in the mid-60's SOC.

    In the summer, the car is panting by the time I get home (1,000' elevation gain in 25 miles, upper 90's F ambient temp), so I immediately give it about 45min of Range charge. That cools things enough that the circulation pump is able to shut off, and it keeps my electric bill lower vs doing the full charge that way. I also don't have the extra hours of noise with the fans and A/C blowers going in the evening. Doing the cool-down right when I get home limits the time the battery simmers in an elevated temperature state. Seems prudent, even though it's not hot enough that the car would initiate a cool-down on its own. My battery is original (2010), with 35k mi on it, and a standard charge nets me about 170+ mi in the winter, a bit less in the summer. Trying to be as nice to it as I can.
     
  5. supersnoop

    supersnoop Tesla Roadster #334

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    This is one of the major benefits of an OVMS module. You can program it to cool down the battery without actually charging.
     
  6. gregd

    gregd Member

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    As soon as the new model comes out, I intend to invest in one for exactly this reason. Also it's annoying to have to remember to go out and stop the charge, hope it's been long enough, etc.
     
  7. wiztecy

    wiztecy Active Member

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    #7 wiztecy, Apr 24, 2016
    Last edited: Apr 24, 2016
    I cool the pack anytime if a 220v charger is available and the battery is above 28C, some people wait until 30, 32.... I won't charge if I have enough charge in the battery for that when I return by the end of the next day my SOC will be 50%+. This is dependent on temps, the more stressful demands I make of the car/pack and/or if the temps are elevated such as in summer temps, I'll bump that return SOC number up to 60%.

    As for the car maintaining the temps of the battery while sitting and not on the charger, all its doing is moving hot water through the pack's core unless the battery temp exceeds 40c, then the AC/Condenser kicks in to chill the pack (unless exceptions like performance mode, then that number's higher.). People call that a hot bath. That type of cooling is better than no cooling and fairly efficient on the battery drain. Reason you want to chill the pack is that degradation is increases as the temperature increases above 26C, and the higher the temps, the degradation turns exponential. You do add more wear and tear to your contactor, but I feel that the battery is the hugest cost and investment so that's where my focus is.
     
  8. gregd

    gregd Member

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    So, long time question I've never asked... how does one know the actual temp of the battery? All my display has is little boxes. Does this require the OVMS module, or is it simply a setting I haven't found yet?
     
  9. wiztecy

    wiztecy Active Member

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    Temps are displayed in the backend/Diagnostics, if you have a 2.x and the VMS is set to debug mode the temps will be displayed in the user menu next to those boxes you described. Unfortunately the 1.5's never received this feature.... With that on the 1.5 the easiest way to view temp data is through OVMS.
     

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