Cold weather battery strategy

Discussion in 'General' started by WA7S, Nov 8, 2022.

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  1. WA7S

    WA7S New Member

    If parked overnight outside in very cold weather, with no external power available, no garage, and the next plug-in at a distance, is there a best battery warming or driving strategy that can improve range?
    Apart from the usual (minimize cabin heat, drive slowly, general hypermiling techniques) is there anything else at our disposal?
    Assume that delaying to mid-day for warmer temperatures is not an available option.
    This is for a VW ID4, AWD.
    Does it help the battery pre-warm itself if you program a departure time in advance (with climate control turned off)? Would that hurt or help range?
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  3. Puppethead

    Puppethead Well-Known Member

    I've gone through two typical but really cold winters, well below zero with my MINI Cooper SE BEV. I leave my SE parked outdoors all day with no charging, so I've got experience with cold-soaked batteries.

    Cold doesn't hurt the batteries, but it slows the chemistry down so you'll (temporarily) lose output power and it will take longer to charge until the batteries warm up. Strategies for extreme cold that I use are:
    1. Charge and/or climatize the cabin (uses the high voltage batteries) just before departure to warm them up.
    2. Park in the sun during the day as much as possible.
    3. Do a mid-day charge to warm up the batteries (I go to a public charger for about half an hour).
    I ran a cold-weather test of disabling all heating at -3 ºF which showed range is affected mostly by use of the cabin heater, the car itself only loses a small percentage of range during extreme cold (or it could be road conditions/snow tires).
    GetOffYourGas and insightman like this.
  4. WA7S

    WA7S New Member

    Thanks Puppethead, that’s the kind of experience I was looking for.
    Thursday I’ll be heading out into the cold white for a long day on the interstates.
  5. WA7S

    WA7S New Member

    Follow up question:
    If the battery is charged to 80% in the afternoon, then sits unplugged getting very cold all night, and only shows 60% at dawn, what is the impact on range? Will range recover as the car is driven (starting out very cold), if cabin heat is not used? Or, did the overnight cold cause a non-recoverable loss of range (until the next plug in)?
    Stephen Graff likes this.
  6. insightman

    insightman Well-Known Member Subscriber

    @Puppethead's your man for this question. In Minnesota he's driven with the heat off in ungodly temperatures and the windows down to prevent fogging to test the effect of cold on BEV range when comfort is not part of the equation.
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  8. WA7S

    WA7S New Member

    Here's a partial answer to my own question, based on this morning's test.
    The ID4's 77 kwh (usable) battery was cold soaked overnight (20F), unplugged.
    Yesterday's charge to 80% had dropped to 78% overnight, presumably just due to the cold.

    Starting out before sunrise, a layer of ice on the windshield melted quickly, that's nice, one minute and you're ready to roll.
    That minute of warming up everything dropped the battery 1%, to 77%.
    And just sitting there, the predicted range dropped from 172 miles to 143 miles.
    (For comparison, at 80% charge in 35F weather, plugged in, the predicted range is usually about 190 miles.)

    The camera that reads speed limit signs is located behind a small mid-top piece of the windshield.
    That little piece doesn't defrost as fast, so hand scraping helped there.
    The outside mirrors do defrost: the control is not haptic (like too many others in the car) so pressing it does nothing; you have to rotate the mirror knob.

    The ID4 predicts range based on recent use, so the numbers are low at first (after defrosting), but then climb.
    To minimize electric cabin heat, don't turn down the temp to "LO", that turns on the AC (unless AC is manually turned off) and lots of fan air.
    Instead turn off the climate control entirely.

    The ID4's predicted range did climb, as the miles accumulated; when added to the accumulated miles the total varied between 195 and 201.
    (That's more than the predicted 172 or 143 I started off with.)

    The ID4's predicted range changes instantly and significantly when the climate control is turned off. Or on.
    A couple of pairs: 188 with climate off; 171 with climate on. 156 off, 136 on.

    Neither the heated steering wheel, nor the heated seat, make any change in predicted range.
    So presumably they draw little current. Despite making the driver quite comfortable.

    Over 29 cold miles (no net elevation change, speed averaging 55), using some cabin heat intermittently, actual miles/kWh including warmup came to 2.4.
    This, for an ID4 which has averaged 3.4 over 2,114 miles in fall weather, mostly highway.

    The wind noise is a bit louder, when the car exterior is covered with thousands of little bumps of frozen ice.
    (Remember the Moody airplane, which increased range by using flush-mounted rivets to reduce drag?)

    On icy roads, the ID4's subtle drive train interventions are distracting.
    I'm used to gauging ice/snow/traction on the highway by the tiny changes felt at the steering wheel, as individual tires encounter varying surfaces.
    But the self-adjusting changes made by the drivetrain reflect its own compensations, not the road variations I'd prefer to sense myself.
    If either form of the stay-in-lane programming is on, those inputs add to the mixed messaging.
    So the driver loses touch with the road some, leaving less feedback about the available friction, though more about the drivetrain's tiny compensations.
    Perhaps a driver can learn the new felt language, over time, but for now I'm at a disadvantage.
  9. Puppethead

    Puppethead Well-Known Member

    It sounds to me like the ID.4 might have some sort of battery conditioning that runs automatically? That might explain the small SoC drop. But I know nothing about the ID.4. Certainly I wouldn't expect to lose 2% battery sitting in 20 ºF temperature, which I wouldn't classify as "cold" as far as batteries go. In my SE I never experience cold battery issues until below 0 ºF.
  10. GetOffYourGas

    GetOffYourGas Well-Known Member

    I am not familiar with the ID.4 either but suspect battery conditioning as well.

    I have a Bolt and an SE. the Bolt has battery conditioning and the SE does not. I often see a few percentage points lost in the Bolt after cold soaking overnight in those temps. I don’t see the same in the SE despite a battery that’s 1/2 the size.

    Of course battery chemistry could also be in play.

    Sent from my iPhone using Inside EVs
    Last edited: Nov 11, 2022
  11. bwilson4web

    bwilson4web Well-Known Member Subscriber

    “SE” is ?

    Bob Wilson
    electriceddy likes this.
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  13. GetOffYourGas

    GetOffYourGas Well-Known Member

    Sorry, Mini Cooper SE

    Sent from my iPhone using Inside EVs
    bwilson4web likes this.

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