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Charging when it's hot outside

Discussion in 'Prime Main Forum (2017-2022)' started by Digloo2, Aug 5, 2018.

  1. Digloo2

    Digloo2 Active Member

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    I live in Phoenix, AZ. It's 1AM right now and 95 degrees F outside. The high today was 115F.

    I usually charge my Prime at night because it (theoretically) cools down. Well, 115 to 95 is a 20 degree swing, after all, so you can call that "cooler".

    Anyway, I'm noticing lately that the LEDs on my power brick start flashing after a while, and it takes longer to charge. I've learned to tell the car to turn on the A/C when it's charging; I'm not sure it does turn on the A/C all the time, but I'm curious if there are other parts that just can't handle the heat very well.

    I mean ... if it's just plain HOT outside, will the A/C be of any use while it's plugged in?

    Are there temps beyond which it's not recommended to charge?
     
    #1 Digloo2, Aug 5, 2018
  2. jerrymildred

    jerrymildred Senior Member

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    It will slow down the charge rate if the battery gets too warm. If it's in an enclosed garage and you use the A/C, you're working that A/C pretty hard.

    I don't know of any published temperature limits for charging. AFAIK, it just gets slower with rising temps. Hottest I've charged my PiP in at is about 95F. I didn't notice a slowdown even with an L2 EVSE.
     
    #2 jerrymildred, Aug 5, 2018
  3. pineprius

    pineprius 15th Hole #4

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    You may want to set the car charger to 8A max and see if that helps. Takes longer but not an issue if you charge with a 6am ready time.
     
    #3 pineprius, Aug 5, 2018
  4. Dudley1030

    Dudley1030 Active Member

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    Yea, it may be 115, but it's a dry heat. ;););)
     
    #4 Dudley1030, Aug 5, 2018
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  5. bisco

    bisco cookie crumbler

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    try using the charge timer, so it starts charging as long as possible after you have driven it.

    i would look up what the blinking brick lights mean in the o/m.
     
    #5 bisco, Aug 5, 2018
  6. Digloo2

    Digloo2 Active Member

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    I've opened the door to see the charge time remaining while the lights are blinking, and then I unplug and replug the cable from the wall and look again. While the lights are blinking, it's twice as long as when they're not. (This has been for 120V.)

    So I'm thinking the blinking lights might just be an indicator that the car or EVSE automatically cut the charge current in half.

    A full charge at 120V / 8A is about 10 hrs. At 240V it's a bit over 3hrs when it's hot out, and about 2-1/2 when it's cooler.
     
    #6 Digloo2, Aug 5, 2018
  7. bwilson4web

    bwilson4web BMW i3 and Model 3

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    I'm doing a study of hot weather charging and have some questions:
    • How are you measuring the time?
    • Do you have any temperature metrics beside 'hot' and 'cooler'?
    • Were all metrics taken with the car limiting charging to 8A?
    I am using two sources:
    In the current phase, the car sits on the driveway with charging starting at 3-4AM. This allows the car to cold soak in 70-80F (21-26C). I'm looking to find a baseline charge at the maximum the car allows.

    One challenge is finding some way to automatically record air conditioner operation. I'll look for a fuse.

    Bob Wilson
     
    #7 bwilson4web, Aug 6, 2018
  8. Digloo2

    Digloo2 Active Member

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    Not sure what your point is here, Bob. I'm sure there are ways to measure things down to the millisecond and tenths of a degree over time, but I don't find that degree of accuracy makes any difference in the net effect, which is that it takes longer to charge when it's HOT outside.

    Phoenix is HOT this time of year -- lows between 85 and 95, and highs between 108 and 120. Measuring it more accurately over time is not going to make any difference -- it's 5AM here in Phoenix, the temperature in my driveway is 90, and the humidity is 35%. At 3AM it was 92. (I have indoor/outdoor temperature sensors.) This is how we define "cool" this time of year. Knowing it's really 90.3 is not going to impact anything in the least. It STILL takes nearly 10 hours to charge right now at 120V. I don't need to measure that down to the minute, as 15 minutes one way or the other is irrelevant to me.

    This weather is typical for Phoenix during the monsoon season. The car said it was 118 for quite a while as I was driving around after lunch, but I don't charge it mid-day.
     
    #8 Digloo2, Aug 7, 2018
  9. benagi

    benagi Active Member

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    Wow, 10 hours to charge. I guess the heat does take a toll on how long it takes to charge a dead battery. Mine is taking just over 6 hours in the garage at 3:00am, approx 80 degrees.
     
    #9 benagi, Aug 8, 2018
  10. m8547

    m8547 Senior Member

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    The included charger brick has a temperature senor in the plug that plugs into the wall, and it will slow down or stop if that part gets too hot. I can't remember if they list a cutoff temperature for that.

    I've only seen mine use the AC twice while charging, but it's only been up to about 95 here. It asks about half the time I shut the car off, but the times I've seen it run is usually when I just used all the EV range in one trip, so the battery is warm internally. One trip was up a hill for 10 miles then back down. If you've been driving moderately with the AC on, the battery won't be that warm when you park. Of course it will warm up as it charges and as the car sits in the heat.

    The AC probably uses around 1KW depending on how hard it's working, so if you're charging on 120V that doesn't leave much power left to charge the battery while its running. So of course it will take longer.
     
    #10 m8547, Aug 8, 2018
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