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Battery Charge Loss: Overnight

Does anyone else notice that their Model S loses charge over night? I went to Tesla Menlo Park yesterday and told them this, but hey said that the charge loss would replenish itself once I started driving. They explained that this was due to the cold temperature at night, which caused a misreading in the morning. My takeaway from the conversation was that the battery under cold temperatures acts similar to that of a car driving up or down a hill: the "gas tank" misreads the level of fuel in the tank.

So I took my car home last, checked the mileage, went to breakfast this morning, and not only did the car register 30% less charge but it did not replenish. It also lost 2 miles of charge for a 1 mile trip. I drove normally. I checked my phone and it had been logged in to when I checked the mileage last night before I went to sleep: 61 miles
It changed to 38. It was at 40 before I drove to breakfast.

I believe it lost 30% the previous night. 102 went to 70 something.

I just picked up my car from the factory on Thursday 2-14-13, so I'm a little new to this. Does anyone else have this problem?


Here's the latest...(click for a bigger version)...another day and a half to go. Good thing is I'll only use about 60 miles to get home.

Uploaded from Photo Slice

Here's my update. The post I had earlier was on the old 4.0 software. So just to make it current and fair I left it unplugged again to see my daily losses with the new 4.2 update.
Garage temps are at 57 Deg...
Pulled in with exactly 100 miles to go.
Next night at same time had 87,
Following night, same time was 75.
It seems to me, my losses are the same regardless of software updates so far. I also thought that it might be less if battery levels were lower as it might try to 'survive' at some point and draw less power. I also used the app to check levels this time, where as before I had to open the door to check it and the car would wake up.

Picked the car up this morning. Here's the full week's results:
Uploaded from Photo Slice

Miami this week was 70's during the day, and 50's over night. After initially losing 0.6 m/hr in the first 12 hours, it settled down to a (fairly) steady 0.4 m/hr for the rest of the week (horizontal axis is time)


This seems really, well, bad... I'm no expert, but if my calculations are about right, they mean there's about a 140 watt draw while your car is parked (in whatever state it's in). Here's what I did:

-you lost 189-131=58 miles of range.
-at an average of say 350 watt-hours per mile, that 58 mile loss is equivalent to 58 X 350 = 20,300 watt-hours.
-you lost this amount over about 6 days, which equals 6 x 24=144 hours.
-20,300 watt-hours divided by 144 hours = 141 watts.

Could this be right? - could the car be consuming 141 watts while parked?? If so, that's way too much...

Wow. TM needs to get the sleep function back in service ASAP.

Yup. TM knows it. They are keeping everything running at full power all the time. As soon as they get sleep mode reimplemented in the firmware the drop should be closer to 25-30 w/hr.

It's unfortunate that all the controls have to be on the display, otherwise they could add a physical switch that disconnects the 12V battery. Like any ICE car.

@nickjhowe - great information and presentation!

Thanks Got Amped.

@Hans - except the switch doesn't disconnect completely. The battery on an ICE car still powers the alarm, the remote key sensors, the lights,... All the key does is shut down the switched 12V circuits.

The S uses contactors to isolate the battery (and by the sound of it different elements within the battery) and has switched 12V circuits like an ICE car - try using the cigarette lighter when the car isn't on.

To get the best user experience they decided to keep all the computers powered on all the time - I guess they didn't figure that many people would leave the car not plugged in for a long time (bad assumption) or that it would draw quite as much as it does.

Clearly they know how to fix this (it was fixed in 4.0), but didn't quite get enough bugs out.


Thanks for explaining.
Indeed I will keep my Model S unplugged for most of the time, since I only can use public chargers. I have had no problems with my Nissan Leaf doing this so I am a little worried with the Model S. Hope they will fix this.

Note that getting the sleep mode back functioning may very well disable the Mobile App.

They should implement sleep with a periodic heartbeat, which would allow communication with TM and also the mobile app. The app communicates through a TM system, and there's hardly any info exchange needed. This could be a very low for car->TM, and fully wake the computer only if the mobile app needs to dynamically connect and perform an to turn on climate control. Else stats could be proxies by TM server.

The mobile app also goes offline whenever the car is out of cell phone range. This is to be expected, but is an issue at a lot of EV charging stations. For example, I left my S at the BWI daily garage this week for a couple days. The EV charging stations at BWI and at most garages are on the lowest level, in this case in the basement where there is no cell service. So I wasn't able to check on my car with the app at all. I suspect this is the case at many garage locations, especially under buildings.


Do you recall, once the car got warmed up and was driving, did the picture look similarly or did add some miles? It would make sense to me that, while it is sitting there, it thinks it can't go as far as it really can, again just like a gasoline car driving downhill or up in incline and engage tips one way or the other. Let me know if you noticed anything at all or maybe it's slipped your mind by now.



I like how you took the snapshots. This could be really useful to all of us and maybe we should start a new thread with just this type of information. Any thoughts from anyone else?

@drp - when I got to the car in MIA, the ambient was already c.65° so not much range to be gained by warming, it at all.

I had my parking sensors installed this past week. Initially we thought it would take two days, so I brought it in on Thursday morning, to pick up Friday afternoon. So I didn't bring my charging cord. However, it took longer and they had to keep the car over the weekend, when they don't work. So they finished this morning - total of 4 24 hour days without a charge. The car was kept in their garage, with typical night time temps in the low 60's. I went from 198 to 135 in the four days, without the car being driven. They did use some power to test the sensors, but I think it was nominal. Anyway, it looks like a loss of 16 miles per 24 hour day. I checked remotely every night and the loss looked pretty linear. I have a standard MS85 pretty well loaded.

I noticed this morning via the app that my car dropped from 235 to 165 overnight. The car is at the Rockville service center, and I can see that the doors, hatch, and frunk are all open, as is the charge port. It is very cool to know that the car is actively being worked on. They must have driven a bunch of test miles to kill off that many miles since last night.

New function for the app: odometer reading

And/or current current use! The "teenager surveillance function".

The quick-and-dirty estimate I've been using: 0.5 mph loss while parked. Goes up and down with temperature, but I think that evens out when battery warms up after starting.

Wow, dont have all the inter-day details , just went on a quick trip and left her outside unplugged in the DC area Fri morning to Tues morning . Roughly 45 to 25 degrees F daily. Ideal went 261 to 195 . It is worse than I saw in the fall so cold does have an add'l effect. V4.2.

Probably, it's partly because the car doesn't know when you're going to want it again, and keeps the battery from dropping all the way to ambient outdoor temperature. When timing is available, you can let it drop all the way down; cold itself is not harmful, and will not reduce range. Charging and driving when cold is harmful, though, so allow enough time to pre-warm (preferably on "shore power") after a long "cold soak".

Actually, after any length of "cold soak" it should be pre-warmed if possible. Starting out immediately when cold will cause the car to dump huge current into the battery heating system for a while.

@Nick - Excellent post, thank you! I live in the same area and experienced the same issues these past 2 weeks with the temperature drops, losing as much as 14 miles a night (7 PM to 7 AM) when the temperatures reached the low 50s. I was also concerned and wondering about the losses, which definitely distort what Tesla promotes in terms of idle discharge rates, monetary savings and the general range of the car (when taking into account separate short trips over a period of weeks rather than a single long trip). I hope they come out with the next firmware version soon, and that it addresses the sleep mode and any other charge loss issues. I would certainly suggest to enable smart sleep modes, in which they allow most components to go into sleep mode but perhaps the vital ones necessary for a fast start-and-go to remain more "alert" for needs. Also a programmable timer on sleep mode would most probably take care of 90% of the problems, as most of us can easily predict 90% or more of our cars' idle times.

At the Tesla Oslo event last night Elon said Tesla currently expects cars to lose 2-3% battery capacity each night (seems too optimistic based on our experience), and this will drop to 0.2% when they re-enable sleep mode.

At the Oslo event, Elon said sleep would return before shipments to Europe began in July.

@Nick: Very excellent and timely post. I'll be parking my car for 7 1/2 days at Orlando Airport next week and this was exactly the real world data I came looking for today. Thanks.

If I read it correctly, your car lost 58 miles in 6.5 days. That means 8.9miles/day => battery would be empty (from full 265 to 0) in 29 days. That is parasitic load of 3.36% per day. More than Elon stated in Oslo (2-3%), but not that much more :-)

However I agree, sleep mode is needed.

@Jolinar - I wonder how long that same drop would continue, and whether it would go down to zero. At some point the car goes into battery save mode. But I don't know when that would happen.

98% of the time I plug my car in at night. On the few occasions I left it unplugged overnight, it lost about 10 miles of range in 30 F temps. I'm in Ohio. I have noticed on really cold days 12 F while parked at work I would get home with 150ish miles of range out of the 230 I had in the morning. That is a 42 mile round trip. 50% highway. So some was warming the battery after i started driving and some was loss while sitting. The android app wasn't released until after our cold snap so I wasn't able to pre warm the car. In the really cold temps my wh/mi were around 550 and in 45 F or greater I use about 300 to 350 wh/mi... depending on how heavy my foot is on the highway :) Usually drive 80. I have found that 45 F seems to be the tipping point for using more energy to warm the battery... at least that is when I notice the wh/mi going up.

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