# Cold-soak trip



## bwilson4web (Mar 4, 2019)

About 8:30 AM, my wife announced she needed to be in Murfreesboro TN, ~91 miles away for a 10 AM grandson game. I had increased the SOC from 67% to 75% and it indicated 164 miles. But I had not anticipated:

+20 mph, 26 F, headwind
need to be there at 10:00 AM so I drove 75-79 mph
car had cold soaked overnight
The navigation system routed us via Manchester SuperCharger bumping the distance from ~91 miles to ~118 miles. The lifetime 229 Wh/mi became 364 Wh/mi, a 59% decrease in efficiency. We missed the game but thanks to AutoPilot and the Manchester TN SuperCharger, we arrived in Murfreesboro. Picked up her grandkids and returned via Manchester SuperCharger. She has been work two jobs so I and AutoPilot did all of the driving.

On the trip:

364 Wh/mi * 118 mi ~= 43 kWh, 86%, for aged ~50 kWh pack after 60 k mi
So I'm increasing my charge level to 90% during the winter. If we need to make another, unplanned, subfreezing dash into a headwind to Murfreesboro, we should be able take the shorter, direct route without having to route via a SuperCharger.

One late thought is to schedule preconditioning departure at sunrise, 6:45 AM. For the cost of some electricity, the car should be ready to go in daylight and last through most of the morning.

At 3:30 AM, it is 24 F outside and the car has been cold soaking since I got home about 4:00 PM. So I've scheduled pre-conditioning for 6:45 AM. My JuiceNet 40 Pro should record the amount of energy need.

I've got a preconditioning power graph:

Scheduled for 6:45 AM, 25 F external temperature
5:40 initial block to top off the cold soak battery
5:45 steady 3.8 kW to warm the battery?
6:25 variable slope consistent with cabin warming
6:45 block to top off the warm battery
6:55 taper to maintain cabin warmth
7:05 end of cabin temperature taper








Bob Wilson


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## Ed Woodrick (May 26, 2018)

I would recommend keeping at about 90% all the time, but in this case, pushing it to 100% before the trip. That tends to be the recommendation of Tesla.


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## bwilson4web (Mar 4, 2019)

Ed Woodrick said:


> I would recommend keeping at about 90% all the time, but in this case, pushing it to 100% before the trip. That tends to be the recommendation of Tesla.


I appreciate the suggestion. Just I was following a recommendation by the late Jack Richard who recommended keeping the battery as close to 50% as practical. This should avoid higher voltages at the ending SOC. My understanding is a higher voltage difference can induce more SEI formation, locking up Li, than a lower charge rate.

Bob Wilson


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## garsh (Apr 4, 2016)

bwilson4web said:


> I appreciate the suggestion. Just I was following a recommendation by the late Jack Richard who recommended keeping the battery as close to 50% as practical.


If you had another choice for such a last-minute trip, then that would be fine. Or if you had a supercharger nearby that didn't require you to travel so far out of the way. But given your situation, I agree with Ed. The differential increase in lifetime battery degradation is worth it for your and your family's convenience.


__ https://twitter.com/i/web/status/1118225459416682496


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## bwilson4web (Mar 4, 2019)

garsh said:


> If you had another choice for such a last-minute trip, then that would be fine. . . .


We also have a BMW i3-REx and I'd expected her driving to Nashville using the Range Extender engine. But she did not feel comfortable and asked me to drive us up and back with the Tesla. The Tesla worked not as fast as the BMW due to the extra SuperCharger session but with me and AutoPilot+FSD, safely. Best of all, I learned lessons about Tesla cold weather driving.

Bob Wilson


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## Ed Woodrick (May 26, 2018)

bwilson4web said:


> I appreciate the suggestion. Just I was following a recommendation by the late Jack Richard who recommended keeping the battery as close to 50% as practical. This should avoid higher voltages at the ending SOC. My understanding is a higher voltage difference can induce more SEI formation, locking up Li, than a lower charge rate.
> 
> Bob Wilson


Yep, possibly. And you may decrease the life of the batter from 300,000 miles to 299,000 miles. Odds are, you are going to get rid of the car way before the battery decreases much.


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