How long should I wait before charging?

Discussion in 'Prime Plug-in Charging' started by Shameless, May 9, 2018.

  1. Shameless

    Shameless Member

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    Surprised a search didn't turn this up, but what's a reasonable time to wait after driving before an immediate recharge? I just got home from a short drive, and I'll be going out tonight. I want to get some amount of cold soak for battery longevity's sake, but the sooner I plug in, the more EV happens later. So how long is a reasonable minimal amount to wait before I plug in?
     
  2. 2k1Toaster

    2k1Toaster Brand New Prius Batteries

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    Don't worry about it. The degradation due to heat is basically nothing up until the batteries are super hot. And this super hot point is handled by the on-board battery management system (BMS). Just plug it in, and the car will charge as long as the battery is cool enough, and if it is that hot it will charge at a reduced rate or wait for it to cool. Just like if the battery is too cold, it will trickle it up a bit then start hitting it with higher current. All of this is taken care of, you don't have to overthink it.

    I actually cannot even think of any possible way to get the Toyota Prius Prime battery hot enough for it to downgrade charging. A hot Nissan Leaf in Equatorial sun can be CHAdeMO charged at 50KW immediately after doing high speed highway driving with the battery temperature only being high but doable. It usually takes another high speed run after the full power CHAdeMO charge to another CHAdeMO charge before the over-temp would kick in. It's just not possible on the Prime where you can't charge it anywhere near that quickly. It should be close to ambient by the time it is full.
     
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  3. Shameless

    Shameless Member

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    Wow-- the things you find out around here! Thank you. This prompts another question -- why does the battery not "like" to sit around full?
     
  4. bisco

    bisco cookie crumbler

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    lithium degrades over time, and the fuller it is, the quicker it degrades, shortening both the life of the battery, and the useable capacity.
    that's why toyota provides a charge timer, so the battery won't sit full every night for a morning departure.

    regarding your original question, wait as long as you can, but allow yourself enough time to get a full charge, or at least the amount of charge you need for an ev only drive.
     
  5. 2k1Toaster

    2k1Toaster Brand New Prius Batteries

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    Lithium does not degrade at all due to high voltage, the capacity is just fine.

    The higher the voltage the cell is at, the faster the oxidation of the electrolyte. There is no way to reverse this. So if you charge up to 100% (which is less than actual 100% for the pack, it won't let you be stupid) you oxidize more of your electrolyte and therefore your cycle life drops.
     
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  6. Bill Norton

    Bill Norton Senior Member

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    This is why most PHEV's and BEV's recommend having the pack in the mid-range SOC during long term storage.
     
  7. 2k1Toaster

    2k1Toaster Brand New Prius Batteries

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    Yep. It's easier to tell a consumer a number rather than the why behind it. :)

    And of course if you're cell voltage is too low, bad stuff happens too that lowers cycle life. So really it is all about finding a happy medium.
     
  8. DavidA

    DavidA Prius owner since July 2009

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    If it is very hot outside and I've just returned from using the entire traction pack down to near zero, I might wait a while to charge it. But they're right, above, Toyota won't let you charge to 100% and hurt the battery. Some other car brands might allow near real 100%, which is bad in hot weather or storage. 100% in the Toyota world is about 80% of the actual real battery capacity. That buffer allows for nothing bad happening, and helps to extend the working life of the traction pack. 0% also isn't actual 0% -- it is more like 15%.

    Think of it in terms of gasoline tank capacity. Your car says it is time to refill, and your "gauge" has 25 miles left on it. Even if it hits 0 miles, there is about 1.35 gallons left in the tank, for reserve.
     
  9. Bill Norton

    Bill Norton Senior Member

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    Not true.
    You are forgetting some manufacturers have an active Thermal Management System so the battery pack is always kept in a 'Happy Temp Range' if plugged in or the car is powered on. Cools it or Heats it as needed.
    These PHEV and BEV's (with TMS) require no thought or interaction from the driver.
    Just drive it as hard as you like and plug it in when you want!

    It's true most PHEV's do have a buffer at top and bottom of SOC to go easy on the pack. This is one reason PHEV's do not show battery degradation the way BEV's do.
    But then you want to be able to use the complete pack capacity on a BEV.
     
  10. DavidA

    DavidA Prius owner since July 2009

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    If a driver topped off their non-Toyota (let's use Tesla for an example) to 100%, unplugged it, then kept it in the blazing hot sun on a day that was 90+ F, with car off and not driven immediately, then what? No thermal management is available to keep the batteries cooler than ambient temps if not plugged in. So best to charge that car to about 80% for better battery health.
     
  11. 2k1Toaster

    2k1Toaster Brand New Prius Batteries

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    Again, doesn't matter. Charge up the battery to 100% in Siberia and the battery will degrade due to oxidation of the plates. Keep the car in 90F temperatures, it doesn't care much.
     
  12. DavidA

    DavidA Prius owner since July 2009

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  13. Bill Norton

    Bill Norton Senior Member

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    I have read that Tesla has that covered.
    For one thing they give you the option of 80% top up or 100%, just for battery life reasons. I believe the Leaf had that for a few years.

    And supposedly a Tesla at 100% unplugged will, all on its own, power up the TMS to cool the pack until the SOC get's down to 80%.
    How long will that 20% SOC last in Tucson in the sun,,, ??? (Tesla may be the only BEV that does this....)

    As stated in the link above even BEV's have 'buffers'. How much is proprietary amongst the manufacturers.
    From the ^link^:
    An EVs typically only allow 85% of the battery to be user exposed. So when your car says that it is 100% charged, that is 100% of the "user portion" of the capacity. This is done to prolong battery life.

    Also there is a happy range of temps for a Li-ion cell. That is an easy to find fact.

    Having a PHEV or BEV without Active TMS is only a detriment to cell life.
    It is a plus if you are only going by purchase price.
    Think people who only rent a car for 2-3 years at a time. They don't care about 'life'.
     
  14. 2k1Toaster

    2k1Toaster Brand New Prius Batteries

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    Yes. My Leaf has a 80% charge option (which I don't use). But the rumour is they had to delete the setting because it changed the EPA rated range or something stupid like that.
     
  15. CharlesH

    CharlesH CA HOV Decal #5 on former PiP

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    As I heard it, when the Leaf had the 80% option, they had to take that into account in the reported range, which of course lowered the number. By taking out the 80% option, their reported range magically jumped. That fact that charging to 100% is hard on the battery and leads to more rapid degradation was apparently not relevant to Nissan.
     
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