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Battery cooling and energy used

Hi, searched but didn't find exact answer I'm looking for. I recently did a ~3500 mi road trip (Eureka CA to Rapid City SD to Denver CO back to Eureka). Performance was amazing and I was surprised that my lifetime energy use rate went from 328 whr/mi to 322 whr/mi over the course of the trip, when most of it was at 80 mph on I-80-- I was seeing 300 wh/mi a lot of the trip... (I use my Trip A for lifetime usage since buying the car ~2 yrs ago, so this is over less than 20,000 mi). However, we did have 1 concerning incident that could have been a disaster, so I want to be prepared or know when to expect it again in the future. The hottest day of our trip occurred when we were driving South from Rapid City SD down to Denver area CO. We stopped at the Wheatland WY supercharger, and since we needed to get some lunch, potty dogs, shop, we decided to go for a long charge and try to make it to Thornton CO (skip Cheyenne etc.). Wheatland was near 100 F. The car cooling fans kicked on when supercharging and it seems like they never stopped when we left the SC. Going onto I-25 I can see my energy usage is upwards of 450-500 whr/mi. There was nothing special other than the temperature. I got so concerned that I slowed, and we stopped in Cheyenne to charge again because at the rate we were using battery I wasn't sure we would make Loveland, let alone Thornton. We charged to around 80% in Cheyenne and when we got back on I-25, energy used was down in the 325 wh/mi range again. It may have been a little cooler but not by much. Thoughts? Did the battery cooling get "stuck on" at the Wheatland SC? Does cooling kick on like this and use this much energy normally when it's hot out? I am just thanking the stars this didn't happen when were were out in the middle of nowhere between Custer SD, Lusk WY, and Wheatland.
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Supporting Member
Jun 11, 2021
South Texas
I’ve had some issues just with the fans running like crazy when it’s really hot out - late afternoon, 99F+ and sun blazing, car had several hours of driving already. Our main issue was city driving. The car was trying to keep us passengers cool plus cool the batteries at the same time. Seemed to suck a lot of energy. Like >500 Wh/mi.

I noticed at one Tesla SC plugging into their wall charger charging rate dropped from 30 miles per hour to 4 miles per hour on a very hot afternoon, just from the AC running plus battery fan running. We got out of the car which turned off AC, and the charging jumped back up to 30 miles per hour. But then afterwards driving smaller roads across town we used up all we had gained and then some.

Interestingly at other times highway driving we were fine on a really hot afternoon, but usage went way up when we got off the interstate for the couple miles slower driving home. We think that at higher speeds air is forced into the air intake which helps the fan cool the batteries.

We’ve been doing other driving on hot days recently and seen terrific energy usage - less than 300 Wh/mi (22 Model X LR). We aren’t as aggressive with the AC.

Still getting my head around all of this. But it’s interesting that after we started paying more attention to the details, we’ve been getting better energy use overall.

Used a V3 charger the other day but it was only 93F at 10:45am and we only charged to 80%, but I was also in the car so it was keeping it cool. No issues with energy use afterwards even though it was 100F by the time we got home at just before 1pm.

Yes, it gets really hot here.
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yeah the fans stay on for a while and the battery still needs to get cooled down after you leave a SC sometimes especially when its hot. it was 112f here yesterday and i supercharged just fine and the air coming out of the radiator was about 136f which is as high as it ever gets (i have a temp probe i stuck in there out of curiosity), and as always the cabin air was diverted to cooling the batteries for a bit so it was a little warmer in the car than ideal but it was still cooler than having the windows down.
I have noticed higher wh/mi for my LR in the past few weeks where temperature is consistently over 100 degrees. However, there are many other factors that affects the efficiency than the temperature (even assuming you are driving similarly w/ speed constant). Wind, tire condition, HVAC usage, load, etc. For me the most prominent factor is probably the gradient of the road. Going up an unnoticeable uphill can have great consequences on your wh/mi. Likewise in reverse for a long stretch of downhill (even w/ sections of uphill in b/w). This is why I always only take note of my efficiency on round trips.

As an example, look at my log from Tezlab from yesterday. 3 roundtrips. In Austin no roads are flat and one leg of the trip is almost always higher than the other.


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