Tesla Mode S: 20,000 EV miles loss due to vampire drain

I'm not going to sweat it, mostly because I don't own a Tesla.

But further because the action you describe is simply inherent to the design of the vehicle. The minimal loss of battery charge is happening as you say to "power NECESSARY electronics" while the vehicle is off. This isn't something the builders and designers did not expect.

Is it ideal? No. Could it be designed better? Perhaps. Would it be a concern of mine if I owned a Tesla? I don't think so.

Off today is a relative term with a lot of devices, now including cars. We turn "OFF" our Televisions, Modems, Computers, Soundbars, and lights still glow. Things remain in a "ready" state. Completely and entirely "Off" for anything with a computer is a rare condition. Off as a condition is being replaced by "Stand By". And I'm OK with that. Even if remaining in a stand by state results in the use of some power from some source.

 

I was involved with another car manufacturer and thus acquired the specs on the current drain when the '02 model year car was sitting with an old style key out of the socket and ignition switch off.

"The factory technical manual has the following table of total electrical load after the car has been shut off:

(electrical current is worst case, i.e. car loaded w/all options...)

FROM TO mA

0 min 5 min up to approx. 950

6 min 15 min up to approx. 900

16 min 20 min up to approx. 750

21 min 60 min up to approx. 50

61 min until the battery is empty up to approx. 30

1000mA equals, of course, one amp.

If the car had no options whatsoever, the load after 60 min would be 17mA instead of 30mA."

Every car with a setup to allow remote operation of anything drains from some source while it's sensors wait for us to push our fob..

 

For those newer to the Prius fold, the gen2 had a hard shut off for the SKS. If the car was going to sit for longer than week, it was a good idea to turn the SKS off, as it was possible the system could drain the 12 volt battery. It was because of the sensors looking for movement outside the car were always on, and if they did detect something, the system would wake up and ping for the code from the fob. Parked in an airport parking lot next to a busy walk way, and system could draw quite a bit from the battery.

So all cars have some vampire drain on the 12 volt. Which means virtually all of them will have to burn some extra gas to charge up the battery once the car is started. A BEV could use a deep discharge 12 volt instead of the traction pack. That could preserve battery power for range. It depends on what exactly the vampire loads are, and whether the 12 volt is sized correctly for the job. But then a charging system needs to be installed to charge it up. An added cost, that will also increase the total time to charge the car. Not really a factor for overnight, but could cost a few miles at a quick charger or level 2. And then lead acid batteries are quite heavy. Pound for pound, using addition Li-ion cells instead of a lead acid will likely provide the power for the accessories and some additional miles of range over a BEV using a 12 volt for the accessories.

 

The Nissan Leaf has the little solar panel on the roof to help maintain 12 volt conditioning so that sensors and such can continue to function. I'm curious if Tesla will go that route since it has so much extra stuff going on .

 

A little insight here: Vampire Drain | Forums | Tesla Motors

• First one is that the Model S does indeed have a 12 volt battery.
• Second is that the amount of VD depends upon power save and connectivity settings.
• Third is that loss may not be linear. One user reports losing 5 miles the first day, 2 miles on the second and third, and just 1 on the fourth. The car is likely remaining more alert for a fob, or remaining connected during those first 24hrs.
• Final one that sticks out is that car charges the 12 volt from the traction pack. The last post was from an owner that also had a Leaf, and did some experimenting. After being unplugged for a few weeks, the Leaf's traction pack only lost 1% to 2% charge. Much better than the Model S, but its 12 volt was dead. Like the Prius, a Leaf without a 12 volt doesn't start. Even without such a length of time unplugged, regularly letting the 12 volt discharge deeply will shorten its life. So while the VD on the S is irritating and can be improved, getting into a car with some miles lost from the range is better than having one that won't start.

In addition to the final one, Life With Tesla Model S: Electric-Draw Vampire Slain, At Last reports about how a defective 12 volt lead to higher VD from the car trying to keep it charged.

Most losses reported there aren't as bad as the report in the OP, but ambient temperature surely plays a part since it was 11F when the reporter left their car.

 

• ... Nice! Man I wish the GEN II Prius would have had a way to use the traction pack to charge the 12 volt or at least keep it maintained. That could've save me an easy $200 replacing the Prius 12 volt battery . I'm thinking that would more than make up for a good hundred miles + of plugin Vampire loss. Good to get all the facts.
  .

 

That claim of 14 miles of loss after 2.6 days got attention because it was higher than most people see. The claim was sloppily made. This happened in cold winter temperatures. The author didn't bother to say what the battery pack temperature was when the car arrived at the airport. We do know that it cold-soaked for over 2 days and was probably around 10-20F when the started it up and checked the estimated driving range again. So, it's quite possible that much of the estimated range loss was simply due to the difference in battery temperatures.

I don't think this report, by itself, has much credibility.

Also, someone else mentioned that there are indeed driver selectable options to turn off some types of vampire drain when storing the car for long periods.

Still, I agree that Tesla should try harder in future cars to reduce these kinds of losses. The Chevy Volt has very little loss while turned off and I think this is true of other plugin cars also. The Model S is an outlier here.

 

I think part of the the problem is the cell connectivity. Another poster in the thread I linked found his S used 3G even when set to WiFi with a WiFi network present. If the car is in a garage with poor reception, it could be searching for a signal continiously.

 

You know that's not the same thing.

You have to pay for all the fancy electronic doodads somehow. If you turned off all the cool stuff, the drain would be down to 2 EV miles for just the regular battery discharge loss.

I expect my cell phone battery to drain faster with Bluetooth and GPS on. I accept that loss rather than having to turn it on every time I start the car. My old Samsung clamshell with none of those features used to last 5 days on a charge while my smartphone barely lasts 1. If I use my iPhone like my old cell phone, it'll probably last longer.

You can do the same to the Model S. Turn off sleep mode so you have to wait for the car 2 minutes to boot up in the morning. Turn off constant cellular updates and do them manually. Turn on energy saving and whatever else.

 

Lithium-ion batteries themselves have an inherent self-discharge rate of a few percent per month (as little as 1%). That would amount to something like 0.2 kWh per day or maybe 1/2 mile of EV range on a Tesla S85 during longer-term storage.

NiMH cells like those used in a non-plug hybrid reportedly have a self-discharge rate as high as 30% per month.

 

You are grasping at straws.
First, this is an outlier.
Second, as many have mentioned, you can minimize this via settings.
Third, Tesla has addressed this, and I see no reason to believe they won't continue to improve in this area.

If this were a mountain rather than a molehill you would be hearing more about it.

 

On a gas car or standard Prius (not sure about PIP) all the standby electronics running off the 12V will drain the battery and that will put extra load on the engine to bring it back up to a full charge the next time the car is driven. So, one could make the claim that there is gasoline "leakage" when a regular car is just sitting there.

 

When I tested ours, phantom drain was hovering around 16~18 mAmps, with occasionaly spikes up to 40~. Not sure what was going on with the latter.

What I did was disconnect the 12 volt negative cable, then hook up a couple of leads with alligator clamps, one to ground (the negative cable), and the other to the negative battery post. Ran both leads out of the hatch, closed the hatch, then hooked them up to my multimeter in mAmp mode. Effectively making the meter part of the circuit.

 

Yes, I hope they do what they can to minimize vampire drain, but even a conventional ICE car has the same problem to a point. The always on electronics of the car discharge the 12V at a given rate, and extra fuel must be burned the next time you run the car to recharge the battery.

 

Your first post says 5.4 EV miles a day, not 5400 Wh.

If a Tesla is consuming say 300 Wh a mile, the 5.4 EV miles = 1620 Wh a day

 

The battery size isn't the cause. It could be an issue in that its size allowed the designers to be lax on the initial design in terms of VD.

Some of it is on purpose. Tesla chose to have the traction pack keep the 12 volt charged when unplugged and parked. The tested Leaf didn't lose amount of kWH a Tesla did, but the 12 volt died. While it near full range, it needed a jump start to go anywhere. Even if the time left unplugged wasn't long enough to drain the 12 volt, multiple deep discharges will shorten its life.

Some is due to design. The hidden door handles require the S to have a more active fob detection system. It can't wait until someone touches a handle, so it might be scanning near continuously for the first 24 hours.

Doesn't hydrogen permeate through a FCV's tank while it is sitting?