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Tesla Model S Parasitic Drain – The Continuing Vampire Problem

David Nolan's Tesla Model S - Vampire in Disguise?
David Nolan’s Tesla Model S – Vampire in Disguise?

A couple of months ago, a software patch was released to solve the Tesla Model S parasitic drain problem, but did it work as planned?

Parasitic drain, in a conventional automobile, is common and usually not much of a problem on a vehicle that is driven regularly. Some vehicles have so much drain they can’t start after a week sitting, and will probably require a jumpstart.

For these customers who didn’t do a whole lot of driving, I always recommended the installation of a float-charger to keep the battery at optimum level. Electric vehicles are somewhat different, and in the case of the Tesla Model S, the question could still remain, “Do I leave it plugged in overnight?”

The software patch, announced in December, was supposed to solve the problem and cut parasitic drain to a minimum. There was also the possibility that it might lead to a slight increase in startup time [boot time?], but that it will save something like eight miles of range per day.

Apparently the patch caused more problems than it solved, so it was cut out of on the next software update. There is one vocal Tesla Model S owner who seems to think that his car is losing much more than the eight miles Tesla Motors is officially reporting. This isn’t just any vampire you can just put a stick in.

In a blog post, David Noland laid out his overnight power losses, about one mile per hour off the charger, which is about ten times more than Tesla has previously noted. A new patch should solve the problem, but that isn’t coming until July. Until then, should Mr. Noland keep it plugged in? Range, of course, is a small concern, but what about the amount of electricity that is simply being wasted, and the resulting upstream carbon emissions?

Now, I haven’t seen Mr. Nolan’s vehicle and I am not Tesla Motors certified, but as a Master Technician for Toyota and Lexus, I know parasitic drains can come from unexpected sources. I’m certain he checked to make sure the dome light was out and that he doesn’t have the key anywhere near the vehicle while it is sitting, and it could very well be software-related. On the other hand, a misadjusted trunk light switch could easily leave a light on when the trunk is closed. A second key left in the glove box should prevent the car from locking [I’m not sure how Tesla’s keyless starting system is programmed] but could also keep systems awake when they shouldn’t be.

Image©David Nolan

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