Does this make sense?
I have had my Model S 70D for six years, so you would think that I understand how the battery operates in cool or cold weather. But a couple of days ago, I had an experience that makes me think it has either degraded, or I have forgotten how tough cold weather can be.
Here is how the afternoon went, as I remember it.
It was chilly overnight, with low temps in the 30s (F). My car is always parked outside, and I did not have the charging set for preconditioning. The battery was recharged by about 20-25%. In the morning, I only ran one short errand, so the battery was not warmed up by early afternoon, and regenerative braking was very restricted. The air temp by then was in the mid-40s. We made a trip of 13 miles, about 4 miles at freeway speeds and the rest at 30-40 mph. That trip did not result in much change in the restriction of regenerative braking, if any.
We stopped to see a grandkid’s basketball game, so we were there close to an hour. The next leg of our trip was 35 miles, nearly all highway, at freeway speeds, where we stopped at a supercharger. I noticed that the heater seemed to be struggling to keep the cabin warm. It just did not feel as warm as the setting called for. I was surprised that the regen limit did not disappear by the time we arrived. The battery SOC was somewhere around 40%, I think, not very low but we needed some charge to finish our trip and to get back home. Our charge rate was only around 28 kW when I checked it. I thought that was ridiculously low, probably because the battery was cold and it needed to warm up.
Key question -- Shouldn’t 35 miles at 70 mph have heated up the battery enough to get a decent charge rate?
After we charged for a while, the battery was up to about 65 or 70%, I think, and we left. Now the regen limit was gone and the heater worked well, noticeably better.
Our next trip was another 13 miles. We were at that location for a good hour, and then returned home, a distance of 55 miles. During this last leg, the heater worked fine and we had no regen limit for the entire trip.
So, does this make sense? It seems as if the regen limit should have disappeared before the stop to supercharge, and that we should have gotten a better charge rate. And the car heater should not have struggled to keep the cabin warm when the air temp is in the mid-40s. We had plenty of charge. If we were having this behavior at 45F, I dread to think what it will take to drive in real winter weather with temps below freezing! It could be my memory is poor and that this is typical of fall weather, but it seemed worse than I recall from previous years. We got no warning messages, so I doubt there was anything seriously wrong with the heater or the battery heating, but still...
There was another anomaly, too. When we got to our next-to-last destination, the trip data showed we had averaged about 325 Wh/mile, which seemed about right for the speeds and temperatures we were in. But when we came back out, I looked at the energy app, and it said we had averaged only 290 Wh/mi for the last 30 miles! That made no sense. I looked again at the trip data, and it had changed to the lower amount. It does not make sense that we would have gotten efficiency of 290 Wh/mi on a cold fall day at highway speeds! I seem to recall someone posting about erroneous trip data a few weeks back, but this is the first time I have noticed it.
It could be this is perfectly normal and I am in denial about past years, but it did not seem normal.
I have had my Model S 70D for six years, so you would think that I understand how the battery operates in cool or cold weather. But a couple of days ago, I had an experience that makes me think it has either degraded, or I have forgotten how tough cold weather can be.
Here is how the afternoon went, as I remember it.
It was chilly overnight, with low temps in the 30s (F). My car is always parked outside, and I did not have the charging set for preconditioning. The battery was recharged by about 20-25%. In the morning, I only ran one short errand, so the battery was not warmed up by early afternoon, and regenerative braking was very restricted. The air temp by then was in the mid-40s. We made a trip of 13 miles, about 4 miles at freeway speeds and the rest at 30-40 mph. That trip did not result in much change in the restriction of regenerative braking, if any.
We stopped to see a grandkid’s basketball game, so we were there close to an hour. The next leg of our trip was 35 miles, nearly all highway, at freeway speeds, where we stopped at a supercharger. I noticed that the heater seemed to be struggling to keep the cabin warm. It just did not feel as warm as the setting called for. I was surprised that the regen limit did not disappear by the time we arrived. The battery SOC was somewhere around 40%, I think, not very low but we needed some charge to finish our trip and to get back home. Our charge rate was only around 28 kW when I checked it. I thought that was ridiculously low, probably because the battery was cold and it needed to warm up.
Key question -- Shouldn’t 35 miles at 70 mph have heated up the battery enough to get a decent charge rate?
After we charged for a while, the battery was up to about 65 or 70%, I think, and we left. Now the regen limit was gone and the heater worked well, noticeably better.
Our next trip was another 13 miles. We were at that location for a good hour, and then returned home, a distance of 55 miles. During this last leg, the heater worked fine and we had no regen limit for the entire trip.
So, does this make sense? It seems as if the regen limit should have disappeared before the stop to supercharge, and that we should have gotten a better charge rate. And the car heater should not have struggled to keep the cabin warm when the air temp is in the mid-40s. We had plenty of charge. If we were having this behavior at 45F, I dread to think what it will take to drive in real winter weather with temps below freezing! It could be my memory is poor and that this is typical of fall weather, but it seemed worse than I recall from previous years. We got no warning messages, so I doubt there was anything seriously wrong with the heater or the battery heating, but still...
There was another anomaly, too. When we got to our next-to-last destination, the trip data showed we had averaged about 325 Wh/mile, which seemed about right for the speeds and temperatures we were in. But when we came back out, I looked at the energy app, and it said we had averaged only 290 Wh/mi for the last 30 miles! That made no sense. I looked again at the trip data, and it had changed to the lower amount. It does not make sense that we would have gotten efficiency of 290 Wh/mi on a cold fall day at highway speeds! I seem to recall someone posting about erroneous trip data a few weeks back, but this is the first time I have noticed it.
It could be this is perfectly normal and I am in denial about past years, but it did not seem normal.
