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Winter Battery Heating

zcsnyder

Member
Aug 6, 2017
14
13
Washington, DC
Hey everyone, quick question about range degradation/mitigating range loss overnight-skip to the end for the TL;DR:

I’m a firefighter in a suburban/rural county in the mid-Atlantic region. I’m very close to buying a standard range plus Model 3 out of inventory by July 1 to take advantage of the $3,750 tax credit. At most, I have a 60 mile round trip commute, which is normally not a concern. I work a 24 hour shift from 7am-7am, and my only concern/reservation is that in the winter time, if I experience an overnight drop in range of 20-40% and then possibly have to drive an additional 20-60 miles for an overnight/emergency shift and am away from home/without time to go to a supercharger between shifts, I could be pushing the limits of winter range. I recognize that this is an edge case scenario, but given my profession, I have to be prepared for just that.

I won’t have access to a NEMA 14-50 while away from my regularly assigned station, but I will have access to a 120v AC outlet, which I figure I can hook up to with an 8 or 10 gauge extension cable to avoid a voltage drop that’s detectable by the mobile connector. My napkin math tells me that with a charge rate of 3mph with the mobile connector, over a 24 hour period I could regain 72 miles of range which would account for a ~30% range loss in cold weather not taking into account lost efficiency during driving.

Will the mobile connector be enough to offset overnight battery conditioning drain when temperatures are in the teens to single digits?
 

MrMassTransit

Supporting Member
Supporting Member
Mar 7, 2019
299
515
Washington, DC
You will have absolutely no trouble with that commute, even in the winter. It sounds like your concern is driving 30 miles, leaving the car unplugged (worst case scenario) for 24 hours on a particularly cold day, and then needing to drive another perhaps 60 miles, then needing to return home 60-90 or so miles (at which point you'd have time for a supercharger stop, if needed).

If I got that right, you will have no issue at all. Add in the fact that you have a 120v outlet you can charge from during the first 24 hours if needed, and you have even more room to spare. You simply won't see a drop over 40% in 24 hours, particularly in a place like the DC area. This is assuming you don't want to run sentry mode during that time. The worst you'd ever see is a 10% or so drop overnight. That would be about 24 miles on the SR+ - and even that would be insane. I see at worst a 3-4% drop overnight on a very cold night in this area. On a routine 24 hours without using my car, I've been losing less than 1% a night.

The biggest drain in the winter is using heat. That can definitely cut your rated mileage down a lot. In an absolute worst case where you were pressed for range, you can turn the heat off and drive with the seat warmers on (and also pre-heat the cabin when you're at a location where you're plugged in). That uses a lot less energy. But honestly, even that kind of conservation is not needed in the scenario you posed - even without the 120v charging available, I wouldn't hesitate to recommend the SR+ for your situation. With the charging, it is a no-brainer.
 

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