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Discussion Starter #1
The manual doesn't say much about what temp, that I could find, the car won't start unless it's plugged in during winter weather.
Anyone ever not be able to start their Bolt? If so, at what temp. does the car not start unless plugged in.
Asking as it's getting down to the mid twenties at night now and I leave my car in the company parking lot unplugged all day long.
I'd hate to get to my car at the end of the day and find it won't run.
 

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I don't have any direct empirical data. But, my understanding is the car will use battery power all on its own to keep the battery above 40 degrees. You can also precondition before you leave work so the vehicle might start conditioning the battery along with the last cabin heat settings. Car should do fine. This assumes you have enough battery capacity.
 

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Discussion Starter #3
Didn't know that about the below 40 degrees.
So the entire time my car sits at work in the parking lot, when it's below 40, the battery will be draining via heating the battery warm? Good to know!
Always have a full charge when I leave the house, less the hilltop reserve 12 percent reduction.
I wonder at what point the outside temp makes the warning come true that you can't start the car without being plugged in?
 

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Didn't know that about the below 40 degrees.
So the entire time my car sits at work in the parking lot, when it's below 40, the battery will be draining via heating the battery warm? Good to know!
Always have a full charge when I leave the house, less the hilltop reserve 12 percent reduction.
I wonder at what point the outside temp makes the warning come true that you can't start the car without being plugged in?
The manual needs to be more specific. They leave us on our own. Manual says not to leave the Bolt unplugged for extended periods of time with no definition of what they mean by an extended period of time. Other parts of the manual says it will keep the battery warm. The manual says to plug in each night if cold or warm outside. So we have to read between the lines. We all know that if the car's battery is dead that it can't do any battery conditioning. So we speculate that the extended period of time is where the battery goes dead in extreme conditions. In your case, the conditioning should be two to three cycles with 9kw of a heater running for about 20 minutes each cycle. So you lose maybe 60 miles range sitting in the parking lot during a normal work shift.
 

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So the entire time my car sits at work in the parking lot
Not the entire time. Heater will cycle on and off. Others have reported cycles that occur about every 4 hours. And might be on for about 10 minutes. If you have a garage and plugged in at night, your warm 900 plus pound battery will take a long time to cool off.
 

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In your case, the conditioning should be two to three cycles with 9kw of a heater running for about 20 minutes each cycle. So you lose maybe 60 miles range sitting in the parking lot during a normal work shift.
I have been looking at people's overnight charging plots, showing battery conditioning. None have been over 3 kW. I know the cabin heater can pull 9 kW. How do you know the battery heater is pulling 9 kW?
 

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my understanding is the car will use battery power all on its own to keep the battery above 40 degrees.
Not the entire time. Heater will cycle on and off. Others have reported cycles that occur about every 4 hours. And might be on for about 10 minutes. If you have a garage and plugged in at night, your warm 900 plus pound battery will take a long time to cool off.
I knew this cycling happens when it's plugged in, but wasn't aware that it is also happening out in a parking lot. Can anyone confirm that? How do I know it's cycling? At 15°F I have sometimes seen battery conditioning listed as 2-3% when I return to my car after work. But percent is not very useful– how many kWh does it expend on conditioning?

One question seems ripe for an experiment. How long can an unplugged Bolt sit in sub-zero weather before it won't start? You'd need to do this next to your plug. (And be confident that freezing won't actually harm the battery so recharging will bring it back to life.)
 

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How do I know it's cycling? At 15°F I have sometimes seen battery conditioning listed as 2-3% when I return to my car after work. But percent is not very useful– how many kWh does it expend on conditioning?
The battery info screen also shows the number of kWh's you have used. Just multiply that times the percent battery conditioning for the answer.
 

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Parked outside, yesterday, unplugged, at 28 degrees for 8 hours. NO evidence of battery conditioning (0%) upon my restart which was without delay or problem. We will rarely (once every 5 years) get a non-windchill temperature below zero F. I will be garaged (50-55 degrees) almost all nights. I may never see cold-conditioning.

I have heard the coolant circulating when DCFCing in the summer, but since it is not draining the battery to cool itself, it was not recorded as battery conditioning.
 

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How long can an unplugged Bolt sit in sub-zero weather before it won't start?
This will depend on a lot of variables such as starting temp of the battery pack, SOC of the pack, ambient temps, wind speed and humidity among others.

Too many variables to put a definitive statement in the manual.

It does state this:
Parking the vehicle in extreme cold
for several days without the charge
cord connected may cause the
vehicle not to start. The vehicle will
need to be plugged in to allow the
high voltage battery to be warmed
sufficiently.
BATTERY TOO COLD, PLUG IN
TO WARM
This message displays during
extremely cold temperatures, when
the vehicle will not start until the
high voltage battery is warm
enough.
Plug the vehicle in to an AC
charging station and make sure
POWER O is off to allow the
charging system to warm the high
voltage battery, then the vehicle can
be started. DC charging cannot be
used to recover a cold high voltage
battery.
It will go into reduced power mode (with the appropriate warning displayed) before it gets to the "Too Cold to Start" mode.

CHARGE VEHICLE SOON
This message displays when the
high voltage battery is low and the
vehicle needs to be charged.
This message can display when the
vehicle is parked during extreme
cold conditions without being
plugged in. While driving the vehicle
with this message displayed, the
vehicle speed may be reduced until
the high voltage battery is
conditioned.
 

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Discussion Starter #13
I'll keep an eye on this and see what it does. Jan typically is our coldest month here in Portland, OR. Will see and thank you!
 

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Long term storage details are in the manual

Manual says not to leave the Bolt unplugged for extended periods of time with no definition of what they mean by an extended period of time.
Actually, the manual is specific about leaving the car for more than a month, and less than a month. My Bolt EV is presently in storage for six weeks, with the 12 battery on trickle charge, the car unplugged, and the HV battery down to about 3/5 full, as per instructions in the manual.
 

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I have been looking at people's overnight charging plots, showing battery conditioning. None have been over 3 kW. I know the cabin heater can pull 9 kW. How do you know the battery heater is pulling 9 kW?
Maybe I should have been a lawyer instead of an engineer. I just stated what I knew and that's what the heater is capable of. I don't know how they control it. Let's just guess that it is a simple circuit with a temperature switch. Although, we should be able to see a saw tooth pattern once the switch starts cycling. Here's another thread with a graph of conditioning cycles. http://www.chevybolt.org/forum/273802-post20.html
I don't see any saw tooth pattern, but the data rate may be too slow or averaged to show it. That graph is representative of a car sitting outside in 20F weather. 1 hour conditioning with a 3 hour rest for a total cycle of 4 hours. Conditioning took 1.5 kwh in this example. Assume worst case that there's a cycle start when first parked so in an eight hour work day you might get 3 cycles or 4.5 kWh. So based on this, my estimate using full heater power was a little too conservative. As you noted it would be lower. In this case you might lose only 15 miles range during the work day. But, this data is for weather in the twenties. Would need to see how much the cycles change when it gets even colder. Would be fun to do a heat transfer analysis, but sadly, empirical data will soon be available and would be more accurate. What we don't have, is what the car actually does when unplugged. All the data we have is from being plugged in. What someone mentioned @Cehjun http://www.chevybolt.org/forum/273786-post18.html is just look at the kWh used after sitting in the cold.
 

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Parked outside, yesterday, unplugged, at 28 degrees for 8 hours. NO evidence of battery conditioning (0%) upon my restart which was without delay or problem. We will rarely (once every 5 years) get a non-windchill temperature below zero F. I will be garaged (50-55 degrees) almost all nights. I may never see cold-conditioning.

I have heard the coolant circulating when DCFCing in the summer, but since it is not draining the battery to cool itself, it was not recorded as battery conditioning.
Just a quick google on Lithium Ion:
Li-ion Operating Temperature. (may vary from Bolt's chemistry)
Charging: 0°C to 45°C (32°F to 113°F)
Discharging: –20°C to 60°C (–4°F to 140°F)

Obvious why we see aggressive temperature conditioning while charging. Discharging has a much broader temperature range. Meaning one can drive the car with a much colder battery. Regen would need to be restricted if operated below the 32F. Would be interesting if anyone has gotten battery temps from OBD data. @GJETSON posted battery capacity with respect to temperature here: http://www.chevybolt.org/forum/273762-post16.html
Would be interesting what the car actually does. It might be brute force or have a step function with a simple lookup table. Car might condition more aggressively with a higher state of charge (SOC) and then allow the temp to drop once the battery drops to say 40% SOC.
 

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Here's from page 232 of the owner's manual:


Plug-In Charging
This section explains the process for charging the high voltage battery. Do not allow the vehicle to remain in temperature extremes for long periods without being driven or plugged in. It is recommended that the vehicle be plugged in when temperatures are below 0 °C (32 °F) and above 32 °C (90 °F) to maximize high voltage battery life.
 

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Here's from page 232 of the owner's manual:


Plug-In Charging
This section explains the process for charging the high voltage battery. Do not allow the vehicle to remain in temperature extremes for long periods without being driven or plugged in. It is recommended that the vehicle be plugged in when temperatures are below 0 °C (32 °F) and above 32 °C (90 °F) to maximize high voltage battery life.
Here's other relevant manual info:
p.258
Keep the vehicle plugged in, even when fully charged, to keep the high voltage battery temperature ready for the next drive. This is important when outside temperatures are extremely hot or cold. Propulsion power may be reduced in extremely cold temperatures, or if the high voltage battery is too cold. BATTERY TOO COLD, PLUG IN TO WARM will display. See Battery and Charging Messages -> p. 135.​

clearly people will drive these cars to work and it is not unreasonable to expect a car to sit outside exceeding the plugged-in recommended temperature range for at least 8 to 9 hours. The problem is the manual says "long periods" without defining what that means. Clearly a 900+ pound battery will take hours to heat or cool. The other part of the manual states on page 254:

High Voltage Battery During vehicle operation and also during charging, the high voltage battery cells in the vehicle are kept within a normal operating temperature range.​

Does vehicle operation mean when it's being driven? Or does the car "operate" even when "off" as it clearly does for other aspects (OnStar)? Here's a response someone posted from a customer service rep:

It is recommended that the vehicle be plugged in when temperatures are below 0 °C (32 °F) and above 32 °C (90 °F) to maximize high voltage battery life. The Bolt EV’s proprietary thermal management system has been designed and tuned to provide optimal battery temperature under all operating conditions.

To prevent vehicle immobilization in cold temperatures, we recommend enabling Climate Notifications in the myChevrolet app. When enabled, you will received an alert if extremely cold temperatures are forecasted in your area within 36 hours of the time you select in the app. The Bolt EV thermal management system employs a comprehensive set of diagnostic tests to ensure all sensors and actuators are functioning as desired. A "Service Vehicle Soon" light will illuminate if a problem has been detected. To monitor thermal management activity, use the Energy Details screen to see what percentage of your recent energy has been allocated to battery conditioning.

If you have any additional questions or concerns about this, please feel free to follow up with me via private message.

Best,

Amber G.
Chevrolet Customer Care​
 

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Keeping a battery at 32°F (or 40 °F) when it is 0°F outside is (ballpark) going to take 300-500W.

So if your car is sitting out in the wind at 0°F, this might be as much as 8-12 kWh/day, and a 'long period' would be a few days starting from reasonable SOC, not a work shift.

And they say that when SOC<30%, this self-heating when parked does not operate, and the battery is allowed to get colder than normal low setpoint. It can of course still self-heat if you set it to precondition or drive, and it might take a couple kWh to bring the battery temp up. So I would want my vehicle to be above 40% SOC when parked for a 'shift' in very cold weather, if possible.

Li battery electrolytes freeze around -5°F, causing permanent fatal damage. It seems likely that the car would activate heating below 30% SOC when the battery temps got close to some lower setpoint like 0-5°F as emergency protection. I bet the car and app throw some scary warnings under these conditions, which are the only ones dangerous for the vehicle.

It funny to compare all this to the LEAF, which is all passive, no standby losses, and had a crude temp gauge on the dash. Of course it has no setpoints or cycle algorithms at all, and allows full speed charging and discharging and driving at ALL temps. It does have a <0°F emergency battery heater, and might limit DCFC at some high temp redline, dunno. Of course, cold-soaking the battery did hit the range on top of what is being reported in the Bolt.

So I think its important to keep some perspective that all these Bolt battery temp algos are mainly to maintain top performance (like energy recovery and range) and long-term durability, not essential function. My guess is a Bolt with a 10°F battery (from a long cold-soak below 30%SOC) will operate normally, while throwing you (perhaps scary) informational messages to plug it in next time.

The Nissan never had a problem with a battery that cold....just a lot of info messages while you were zipping down the road to your destination. I expect the Chevy will do at least that well.
 
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