So after my trip yesterday up to Delaware, I had a spirited drive back down to DC last night before allowing it to cold soak overnight. I think this case is similar to what Broder did after his charge in Milford, where he would have had the battery nice and toasty, directly before a cold soak.
I just happened to feel adventurous this last night/this morning. (and a little more confident do this with the newer access that I get using the S REST API with some extra information that didn't feel like I had before). I parked my S unplugged, with about 40 miles of rated range, then left it unplugged overnight. It cold soaked down into the mid 20's overnight, and range showed 4 miles when turned on. The battery level was 19 percent at this point in the morning. I then slowly drove the car for 9 downtown city miles then 2 highway, during which the battery level slowly decreased from 19 percent to 12 percent, clearly the pack was warming itself during this time using about twice the energy that I would expect had the pack already been warm. I then plugged the car in to charge.
At the same time, my rated range display went down from 4 to 0 then to "charge now", and then worked it's way back UP to 6 miles of range left.
I think from this that it is clear that using the "rated miles" left to understand the battery state does not provide a linear relationship.
During this time, I also watched the battery display, which always displayed the percentage full from the battery. Normally I'm use to seeing the battery go from green, to yellow, to red. Even while the car was demanding to be "charge now" my battery was still yellow and not red (I believe because the true energy in the battery was never that low).
If you look at the graphs from Broders trip, you can see a similar case where only a few percent or the batteries energy was used up over night (~5%) but the range was brought from about 90 to 25.
I'm not sure if this is exactly the desired behavior. I'm fairly sure what is happening is that the car is trying to account for the extra energy it's going to need to warm the battery pack up, but perhaps it's a bit too much? I'm also not sure if being overly conservative is the wrong way to go on this, but I would like to understand it a bit better.
Peter
I just happened to feel adventurous this last night/this morning. (and a little more confident do this with the newer access that I get using the S REST API with some extra information that didn't feel like I had before). I parked my S unplugged, with about 40 miles of rated range, then left it unplugged overnight. It cold soaked down into the mid 20's overnight, and range showed 4 miles when turned on. The battery level was 19 percent at this point in the morning. I then slowly drove the car for 9 downtown city miles then 2 highway, during which the battery level slowly decreased from 19 percent to 12 percent, clearly the pack was warming itself during this time using about twice the energy that I would expect had the pack already been warm. I then plugged the car in to charge.
At the same time, my rated range display went down from 4 to 0 then to "charge now", and then worked it's way back UP to 6 miles of range left.
I think from this that it is clear that using the "rated miles" left to understand the battery state does not provide a linear relationship.
During this time, I also watched the battery display, which always displayed the percentage full from the battery. Normally I'm use to seeing the battery go from green, to yellow, to red. Even while the car was demanding to be "charge now" my battery was still yellow and not red (I believe because the true energy in the battery was never that low).
If you look at the graphs from Broders trip, you can see a similar case where only a few percent or the batteries energy was used up over night (~5%) but the range was brought from about 90 to 25.
I'm not sure if this is exactly the desired behavior. I'm fairly sure what is happening is that the car is trying to account for the extra energy it's going to need to warm the battery pack up, but perhaps it's a bit too much? I'm also not sure if being overly conservative is the wrong way to go on this, but I would like to understand it a bit better.
Peter