Yes, that is the thermal management system for the battery. It's fine to leave it unplugged, just note that your battery may not be completely full in the morning if it gets too cold and requires power to heat itself.

 

The 2018 Volt Owner's Manual recommends leaving the Volt plugged in when parked in it's primary parking location with a few exceptions:

1) Up to 4 weeks, just leave the Volt plugged in. *

2) If you won't be driving the Volt for more than 4 weeks, then leave the Volt unplugged with 3 bars (30%) state of charge showing on the battery meter.

* Personally I always try and unplug my Volt if there are any electrical storms forecast for my area.

40F is not too cold to charge or being able to use regenerative braking; if you leave the Volt plugged in then the Volt's battery temperature manatement system (TMS) will ensure that the battery does not get too hot or too cold (too cold to charge is colder than 32F, it has to get to -23F before the battery is at risk of freezing.) If you observe the Volt charging in warm weather, depending on the battery temperature, the TMS may wait until charging has been completed to turn on the coolant pump and/or AC compressor to cool the battery; charging is more efficient when the battery is warm.

The Volt may continue to draw a small amount of power (less than 100W) once charging has been completed. The car will periodically balance the cells in the lithium ion battery pack. The on-board charger will also periodically maintain the 12V battery. When the Volt's TMS is heating the battery because the battery is too cold this will draw ~1kW for up to 15 minutes at a time.

Depending on how many miles you typically drive during the day you do not have to plug in the Volt every time you arrive back at home. You might charge every night M-F and then only charge once on the weekend or twice on Saturday and/or Sunday if you do additional driving on the weekend. If you typically drive very short distances each day, especially in spring and fall temperatures, you can skip charging for a day, two or longer and it will not make any difference if you only plug in once or twice a week.

if you are charging using the 120V EVSE that comes with the Volt you will probably want to plug in every evening because it takes many hours to fully recharge the battery (19 hours at the default 8 amp setting, 12-13 hours at the 12 amp setting.) Only use the 12 amp setting if you are certain that there are no other appliances plugged in on the same electrical circuit or you will overload the circuit, trip the breaker. If the outlet where you plug in is old, replace it with a new, high quality power receptacle so there is a tight connection when the EVSE is plugged in. Don't let the EVSE hang from the power plug as over time this will damage the plug.

 

Our nights get down to about the same temperature. I leave my gen 2 plugged in all night. It uses just about 1/2 of a KWH measured at the outlet where the EVSE is plugged in. I am using the stock EVSE that has been converted to 240 V operation. Around here 1/2 a KWH = less than 4¢

One of the reasons that I do this is that the mornings are still cold around here and I like to remote start the car and let it warm up before I leave the house. I would rather have that "warm up" energy coming from the charging cord rather than from the battery where it would be cutting down on battery range.

 

It also maintains the 12v battery when plugged in.

 

. I am using the stock EVSE that has been converted to 240 V operation.

Can you tell me what you are using to convert to 240V operation? And is it the EV Doctor adaptor taking advantage of the universal 120/240 charger that comes with the Volt?

 

If you look at the post from 2Voltfamily, directly above the one of mine that you quoted, you will find that he has links to that conversion process. The process is different between gen 1 and gen 2 models. The process for gen 2 is pretty simple. 1) verify that the EVSE that came with your car is the same as that pictured in the instructions. (almost all are, if the car still has the original EVSE) and then 2) assuming that you have, or will have installed, a 240V outlet near your car, you need to make up a short little jumper cord that has a standard female 110v plug on the end going toward the car, so that the stock EVSE can be plugged into it, while the other end will have a male 240V plug matching whatever plug your 240V outlet requires. The wires that go to the hot and to the neutral lugs on the 110V end go to the two hot lugs on the 240V plug.

The process for gen 1 EVSE is completely different, and you DO NOT want to try the above with one of those!

I don't know anything about the EV Doctor adapter, but yes, this method does take advantage of the fact that the gen 2 EVSE is designed to run on either voltage.

 

About the only time I unplug mine is if there are electrical storms coming.

The temperature conditioning is a good thing during extreme hot or cold.
You'll get more EV range if the car doesn't have to work to normalize temps when first starting up.

 

At 40 degrees (Fahrenheit, I assume), the TMS should not be kicking in at all. It will below 30 degrees or so. The extremely minor power draw is likely just the phantom draw on the EVSE and whatever tiny amount of energy it takes to light the LED on the Volt's dash. Most of this will probably happen regardless of whether the Volt is plugged in or not.

Long story short, leave the Volt plugged in even after it's done charging. The draw is extremely minor.

 

Yes you can unplug the car at 40F. It doesn't really need heating unless it's below freezing. It doesn't really need cooling unless it's over 80F. I always unplug my car after charging (car sits outside, EVSE inside) unless it's below freezing so it's ready to do a reheat in the morning. It never (maybe rarely) gets hot enough here to require cooling (ocean effect). Unplugging the car when unnecessary not only gives the port a better weather seal (I know it' supposed to be all weather) when the charge door is closed but I have an inline rocker switch to protect the EVSE from power surges of power flicking off and on from trees falling on wires or cars running into power poles and knocking out power (both have happened one more that the other). GM recommends leaving it plugged in because they have to assume every owner is a complete idiot and not leave it up to them to decide when it gets too cold or too hot.

 

When I leave for 3 weeks or more I leave it with a partial charge and connect a "battery tender" to the 12-volt battery, via the connections under the hood.