Winter, hilltop reserve, and battery conditioning

[MikeDabrowski2017]

Starting to get those fall nights here in new england that are in the 40s
Won't be long before the freezing temperatures , snow will be here for several months.

Things like best way to manage the battery temp and SOC while keeping the pack warmed and ready
Without always keeping it full or at hiltop level
Will become very important
It seems that as a group we bolt owners do not have a lot of real world experience, since the nationwide rollout
Mostly missed winter in the coldest areas.
Can some of the people with experience share their impressions, Techniques, problems ?

 

[joe]

This won't really be helpful in general, but since I drive about the same amount of miles every day that I can get from L1 charging overnight, leaving the car on the charger all the time starting with ~50% SOC achieves the goals you stated.

 

[DNAinaGoodWay]

People who got one when they first came out last winter might be able to relate how much energy they lost to conditioning, especially when unplugged. GM isn't saying so we'll have to track it ourselves.

I went through five winters with the 24 kWh Leaf and it lost range to the cold but regained it when it warmed up again. It only warmed the battery if it was bitterly cold, -14 or so, not conditioning it like a Bolt. So Bolt should consume more energy unplugged in the cold, but it has a lot more to spare. GM recommends leaving it plugged in, but you probably wouldn't need to.

 

[oilerlord]

I'd echo the last post.

While there aren't a lot of us with experience driving a Bolt in the winter, there are a lot of with experience driving Leafs, Teslas, etc, in the winter. This will be my second winter driving my 28 kWh EV, and the drop in range is dramatic the colder it gets. No EV's range is immune to the cold.

Another member on this board suggests the worst case, cold-temperature range scenario is taking the EPA rating and dividing by half, and from my experience - it correlates with my experience. Here's a chart that's been posted a few times that illustrates how a Nissan Leaf is affected by the cold:

It stands to reason that the Bolt's range curve would be similarly affected by the cold. Let us know how it goes with your car.

 

[MikeDabrowski2017]

I expect a big hit in range.
I am mostly interested in how much energy is used to keep the battery warm and ready.
How long does it take to warm the battery from 20 degrees F.
I don't need to commute to work (retired) but want the car to be ready to drive if I need to run to town .
My typical use of the vehicle may see it sit for severalunch days between use.
Can leave the level 1 or level 2 charger connected, but don't want to leave the battery in a high SOC all winter.
Does the conditioning work without charging?
I am setup with off peak electric rates and a solar microgrid , so managing the energy required for conditioning and charging is challenging.

 

[DNAinaGoodWay]

Again, GM isn't giving us any specifics, but it appears that it will condition the pack wether it's plugged in or not. Over an eight hour shift, leaving it parked outside, unplugged at near zero Fahrenheit, I expect it'll consume a few kWh, but until we track it, or someone reports their experience from last winter, it's an unknown.

In your case, not needing a lot of range very often, I don't think it'll ever be an issue. I wouldn't bother leaving it plugged in just for that.

 

[oilerlord]

Again, worst case...in the coldest of conditions; you'll still get at least 120 miles of range. Not sure if that's enough for your "run to town" or not, but it sounds like you're not planning to put a lot of miles on your car, so it probably is. You've got a big battery, so you likely don't need to worry about it.

If the car is going to sit for extended periods, you do want to avoid 100% SOC. Hilltop Reserve is recommended.

All the standard winter EV techniques apply...if you're worried about range, pre-condition the car so the battery & cabin is warm before heading out.

 

[boltage]

One other variable with cold weather consumption is how much cabin heat one uses.

 

[MikeDabrowski2017]

First frost warning is tomorrow AM
Car is at the hilltop reserve full condition so I will see if the conditioning kicks in

I do a 180 mile run in one day every 2-3 weeks but run to town is 20 mile round trip.
Did the 180 mile trip on a full charge Tuesday
Did highway at 65-70 mph and got 4.5 miles/ kwh
Still had 88 miles of range .
Love my Bolt.

 

[Posatronic]

I got mine jan 9th 2017. Most of the winter. I drive 150~. Miles a day every day. In the ideal temperatures I got 230-235 a couple of time but mostly 220. 23 min are interstate driving at 82 mph. (Loose most mileage/ energy here) in winter it was mostly around 20 degrees but got to 0 a couple of times. It charged to 175-180 on average. The battery conditioning has only activated 4 times. ( first was on 18 wheeler when I had onstar active and tracking my car through Wyoming) I think too many people are worried about this when it just doesn't happen that often. Definitely not enough to drain the battery any significant amount.
That my experience. Take it or leave it but it's real world experience.
Love the car. Love electric cars. Any kind is better than none. Enjoy!

 

[DNAinaGoodWay]

30 F this morning and no conditioning recorded. I used a good bit warming it up before I left, in the driveway, unplugged. IIRR, Bolt doesn't have a heat pump, just a power sucking resistance heater, so in a mild cold it'll use more power. Luckily there's lots to spare.

 

[MikeDabrowski2017]

Thanks for the real world experience positronic
Have not seen a miles/ kwh hit from the cold yet

No battery conditioning yet.

On a 38 degree morning I noticed what seemed to be a reduced max kwh into the motor and lower than normal acceleration rate?

Lithium Batterys gradually loose their high drain capabilities as they get cooler
Probably not good to hotrod when it's cold

 

[MikeDabrowski2017]

Well it looks like we will learn about cold battery conditioning first hand
Friday night is supposed to get down to 13 f and Saturday night to 19 f
This morning it was 29 and I saw no battery conditioning ?
My evse datalogs each charge so it should clearly show if it needs conditioning and how much.
Wonder if the car will show conditioning if it comes from the grid?
Will leave it plugged in.

 

[SeanNelson]

Wonder if the car will show conditioning if it comes from the grid?
Will leave it plugged in.

The display page with percentage of energy used for battery conditioning is showing statistics "since the last full charge". I assume this means the stats won't start being measured until you unplug the car.

I've seen a few percentage points of battery conditioning with the car unplugged and the temperatures just a degree or two below freezing. Based on the percentage and the total kWh consumed it worked out to about 0.5 kWh used for conditioning.

 

[blondejd]

Just got my Bolt, and the weather almost immediately started to drop to near- or below freezing (I'm in Canada, Toronto area). Temperature dropped to 0C (32F) the other day, and without warming up the car before unplugging, I noticed a few percentage points of power used to condition the battery for the first part of my commute.

This morning, with temperatures dropping to an icy -10C (14F), I warmed it up for 15 minutes or so before unplugging, and there was no battery wasted on conditioning.

It did consume quite a bit more kWh on the way in compared to what I saw with warmer temperatures. Not sure how much of this is due to more cabin heating, and how much of it is due to a cold battery?

 

[LeftieBiker]

The car uses resistance heat only, so most of the extra power used was from the heater.

 

[MikeDabrowski2017]

Ok have some data points
At ambient of ~ 20 degrees f
Conditioning used ~ 1kwh/ 6 hours of sitting
http://99mpg.com/blog/finally-i-have-an-electric-car-chevy-bolt/
I expect it works the same when not plugged in
Not as bad as I had anticipated.
The in car energy graph showed no battery conditioning , so it seems that only shows conditioning when it comes from the battery.

 

[DNAinaGoodWay]

From Friday to today mine used 4% on conditioning, not plugged in, at temperatures down to 15 F. That’s about 2.4 kWh or maybe 10 miles tops.

 

[MikeDabrowski2017]

The % of energy used for conditioning is a true % of energy used up to that point relative to total energy used to that point.

I unplugged the evse with the battery full to the hilltop reserve but not finished the conditioning


the circle graph indicated100% energy was battery conditioning and the driving % was 0
soon as I drove away and the driving %
Started to rise the conditioning part of the circle quickly dropped to zero

Another single conditioning was captured this morning
Evse showed .7 kWh consumed in the 30 minute event

 

[GetOffYourGas]

I saw the battery conditioning this past weekend for the first time. It was 23F when I departed. The energy used (% to conditioning compared to the total energy) worked out to about 0.6kWh. It remained at 0.6kWh as I drove, implying that the car did not condition again. This despite being parked at a trail head in 30F weather for about 4 hours. I'm guessing the battery cools off very slowly.