GM Volt Forum banner

1 - 16 of 16 Posts

·
Registered
Joined
·
94 Posts
Discussion Starter #1
Hey gang,

I finally got my L2 charger installed. I went with the JuiceBox Pro 40 which has internet connectivity so you can monitor and track the charging. Last night I got home after a road trip and the battery was totally depleted. I plugged the car in and it charged to full but in both my JuiceBox app and on an actual kWh meter that I have installed on the circuit to the EVSE it shows that the usage was only 15.7 kWh. Both the JuiceBox app and the Chevy app now show the car fully charged (as well as the car itself showing fully charged of course).

What am I missing here? Where were the other 2.7 kWh of energy last night? I would expect the car to take the full 18.4 kWh or at least somewhere close when it is totally empty and running the ICE. I know there is some energy stored for the hybrid mode and recovered from braking and such but 2.7 kWh seems like a lot if it was really holding back that much but not allowing me to use full EV mode anymore.
 

·
Registered
Joined
·
3 Posts
That is expected behavior. In order to reduce wear on the battery the computer will never let it drop below a certain level or charge over a certain level. Completely draining a battery is bad for it as is keeping it fully charged too often.
 

·
Registered
Joined
·
1,890 Posts
The "usable" capacity of the Gen 2 Volt battery is reportedly 14.0 kWh. http://gm-volt.com/forum/showthread...-kWh-from-the-2016-Volt&p=2764754#post2764754

The 15.7 kWh that you observed would be well in-line with this considering that battery charging is not 100% efficient. (~15.7 kWh in, ~14.0 kWh out.)

As mdchaser pointed out, using the full capacity of the battery would greatly increase degradation of the battery. This is especially so with an EREV, which regularly fully depletes its battery. (This is in contrast to a BEV which can get away with using a larger percentage of its battery capacity because the driver will rarely, if ever, fully deplete the battery, since doing so means a dead vehicle and a tow.)
 

·
Registered
Joined
·
94 Posts
Discussion Starter #4
Okay thanks for the info. I guess when I read about how the gen 1 vs gen 2 battery is larger and yields the higher mileage they are already taking into account that reserve in both models (in other words, when they say it gets 53 miles with the new 18.4 kWh battery they really mean it gets 53 miles out of the 15 kWh or whatever it can actually use and they did the same equation with the gen 1 as well).
 

·
Registered
Joined
·
3,193 Posts
Okay thanks for the info. I guess when I read about how the gen 1 vs gen 2 battery is larger and yields the higher mileage they are already taking into account that reserve in both models (in other words, when they say it gets 53 miles with the new 18.4 kWh battery they really mean it gets 53 miles out of the 15 kWh or whatever it can actually use and they did the same equation with the gen 1 as well).
Correct. The Gen II gets an EPA rated 53 miles on ~14.0KWh of EV driving usable battery capacity (18.4KWh total battery capacity).
The Gen I Volt (2013 + 2014 MY) gets EPA rated 38 miles with ~10.8KWh of EV driving usable battery capacity (16.5 KWH total battery capacity).
 

·
Registered
Joined
·
872 Posts
That is expected behavior. In order to reduce wear on the battery the computer will never let it drop below a certain level or charge over a certain level. Completely draining a battery is bad for it as is keeping it fully charged too often.
"bad for it" is a bit of an understatement, actually...with Lithium Ion, completely draining a cell will destroy that cell. It disrupts the catalyst in the cell and puts it in a condition that's unsafe to charge again.
 

·
Registered
Joined
·
788 Posts
Perhaps someday engineers will learn how to use all 18.4 kwh. Until then, we'll have to deal with the confusion. What if batteries were designated by their usable capacity? That would make more sense for now.

This is as if the square footage of a house was measured on the outside of the house instead of actual usable space.
 

·
Registered
Joined
·
872 Posts
Perhaps someday engineers will learn how to use all 18.4 kwh. Until then, we'll have to deal with the confusion. What if batteries were designated by their usable capacity? That would make more sense for now.

This is as if the square footage of a house was measured on the outside of the house instead of actual usable space.
Or even better, the square footage included the ceilings as well as the floors ;)
 

·
Registered
Joined
·
4,405 Posts
Perhaps someday engineers will learn how to use all 18.4 kwh. Until then, we'll have to deal with the confusion. What if batteries were designated by their usable capacity? That would make more sense for now.

This is as if the square footage of a house was measured on the outside of the house instead of actual usable space.
The 14.0 kWh number is only true in theory. When the battery is "full", the car will still regen. So there is additional room up top.
When the battery is empty, and you are running on the 101HP ICE motor, you have 161HP worth of acceleration. You are actually augmenting the ICE with the additional room at the bottom of the battery.

So how much of the 18.4 kWh you can use is a variable, and at normal temperatures, it is a minimum of 14.0 kWh.

Something else to note. The rate at which you can regen or accelerate is based on the 18.4kWh. If the battery was 15kWh, you would probably give up acceleration or regen.

Going back to the house analogy, if you subtract all the door swing area, or countertops from your floor plan, you'd get the true minimum useful floorspace of the house. However, the area where doors swing and countertops can be used sometimes, and other times cannot be used. The Volt is rated by subtracting the door swings and countertops.
 

·
Registered
Joined
·
610 Posts
Their is also limp home mode that will let run off reserve battery capacity 3-5 miles to a gas station after you've run out of Fuel and depleted the normal battery level.


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
926 Posts
DMC5180, is there an indication when you're in "limp home mode"? Have you experienced this yourself? Nice to know we have a backup in case we completely exhaust all our fuel sources.
 

·
Registered
Joined
·
872 Posts
DMC5180, is there an indication when you're in "limp home mode"? Have you experienced this yourself? Nice to know we have a backup in case we completely exhaust all our fuel sources.
It should display a message saying something along the lines of "Engine Not Available - Out of Fuel" or similar. It will also display a message saying the propulsion power has been reduced. I haven't seen either of these personally (closest I've gotten is the guess-o-meter saying "LOW") but I've read both those messages on the forum.
 

·
Registered
Joined
·
1,675 Posts
If carrying it out to three decimal places, the actual usable seems to be more like about 14.4 kWh. I wish it was closer to 18.4, as it would then easily handle the one somewhat common use case where I need to public charge to avoid gas. (SFO airport run - 34 freeway miles each way.)
 

·
Registered
Joined
·
4,011 Posts
If carrying it out to three decimal places, the actual usable seems to be more like about 14.4 kWh. I wish it was closer to 18.4, as it would then easily handle the one somewhat common use case where I need to public charge to avoid gas. (SFO airport run - 34 freeway miles each way.)
*grin* You can use a little gas, or you can move ten miles closer and double your rent.
 

·
Registered
Joined
·
3,181 Posts
Perhaps someday engineers will learn how to use all 18.4 kwh. Until then, we'll have to deal with the confusion. What if batteries were designated by their usable capacity? That would make more sense for now.

This is as if the square footage of a house was measured on the outside of the house instead of actual usable space.
Maybe the marketing folks should stop advertising the full size and only advertise the usable size.
 

·
Registered
Joined
·
610 Posts
Maybe the marketing folks should stop advertising the full size and only advertise the usable size.
Like my 16GB iPhone with 12.28 GB actual capacity.


Sent from my iPhone using Tapatalk
 
1 - 16 of 16 Posts
Top