Self Discharge of EV Batteries - Your Experiences?

[wolverine86]

I have long wondered what the real life self discharge rate of EV batteries is. I realize that it probably varies due to outside temperature and maybe even outside humidity, but what are your real life experiences? How much range do you lose if your vehicle is just sitting around without being charged, not being driven for a week or even a month? Or to put it another way, say you go on a trip for work or pleasure and drive your EV to the airport and leave it in the parking lot for a couple of weeks and you have 150 miles of range when you park it. What would it be after the couple of weeks? 140 miles, 120 miles, or what?

Note that I'm not asking about how much lifespan you have of your EV batteries before they need to be replaced, just how long do they hold a charge assuming that they are in good condition and how much does an EV's range get reduced over time by sitting around doing nothing.

I have no experience whatsoever owning an electric vehicle (not even an E-bike or a golf cart!), so hence the questions! I have only owned ICE vehicles and human powered vehicles (i.e., bicycles!). I do have experience with Li-ion battery powered tools, and these definitely do lose charge noticeably over a month or more. But auto EV batteries typically have much higher voltage and current capacity than those.

 

[alarmguy]

I like your question and I wonder the same thing if we ever got an electric vehicle as a second car because sometimes that second car sits around for a week or two without being used

 

[Cujet]

For those who don't know, the battery drain is setting dependent. Video cameras, recording, data transmission and so on do drain the power. Turning "Sentry Mode" off on a Tesla will help immensely. As it uses between 7% and 14% of the batteries capacity PER DAY.

There is a very well known series of items that need to be turned off if parking for a long time. Although it is good to know that the software will shut down these things at 20% battery capacity.

It is also good to know that these batteries do not significantly "self discharge". The Vampire is hard at work, eating electrons....

 

[OVERKILL]

This is an interesting thread:
Battery Drain while parked | Tesla Motors Club

 

[andrew_j]

A friend left his BMW EV in Montreal QC six weeks and charge dropped 4% this past December

 

[atikovi]

Bought a Bolt 2 months ago. Still haven't picked it up because of a title problem. Took a look at it last week and the range said about 147 miles. When I bought it, the gauge was at 190 something. It does have a replacement battery.

 

[andrew_j]

Bought a Bolt 2 months ago. Still haven't picked it up because of a title problem. Took a look at it last week and the range said about 147 miles. When I bought it, the gauge was at 190 something. It does have a replacement battery.

I wonder if temp at time has something to do with it.

 

[Ws6]

Ive left my ev6 GT for 2 weeks before. It lost maybe 1% or so, but that could also be temp dependant.

 

[Torrid]

I wonder if temp at time has something to do with it.

Temp will accelerate it if the car is set to maintain battery temperature. The cold alone won’t drain the battery, but the related systems will. If it’s really cold then power and regen will be limited while the battery heats, but it would be drivable. I would not recommend leaving it to maintain battery temperature for long periods of time off of some form of power supply.

 

[Kiwi_ME]

... what are your real life experiences? How much range do you lose if your vehicle is just sitting around without being charged, not being driven for a week or even a month?

I rarely drive, perhaps 3,000 km a year and see very little depletion while my Kona EV sits over a week or two unused, about 1%.

The vast majority of that energy is undoubtably used to power the car's electronics during each 20-minute 12V charge process, about 200 watts. The schedule of six charges a day for the first 56 hours calculates out to 0.4 kWh a day. After that it's just once a day, using only 0.07 kWh per day.

In this particular EV, parked in our mild ambient temps there are no other automatic processes taking place.

 

[y_p_w]

There’s a difference between self discharge and parasitic drain. It’s just like any car these days where there are these little things powered off the 12V battery. Only there’s this huge battery and a tendency to run a lot more stuff on the basis having a battery with over 1000 times the capacity of an average 12V car battery.

It’s always running communications, there might be security recording, and emergency heat settings. I’m also sure that being parked in the Mojave Desert in summer means that there’s a combination of increased self discharge coupled with active cooling to protect the battery.

I don’t know how much this really proves, but I remember checking in on my parents’ Tesla Model 3 while it was in a body shop for about a week. It was obviously moved around, but I can’t imagine they drove it much. It was left there at about 87% charge and returned with under 50%. I suspect they left the A/C on several times and never charged it, although I’m thinking they probably had a charger somewhere just in case (they did a lot of work for Tesla).

 

[alarmguy]

Im surprised there arent many responses to the OP. I guess not too many people in here have their EVs sit a long time without a charge or being connected.
Its a good question, lets say you leave your car in long term parking at the airport with 65% charge. What will it be when you return to your car two weeks later?

 

[RhondaHonda]

If I leave sentry mode on I think it uses a few percent a day if parked at the airport, likely because a car drives by in the garage every minute or so so it’s always recording. Without sentry mode on, my experience is that it goes down minimally over a week or so. I’ve never parked it any longer away from home. If parked at home it’s plugged in if I’m going to be away for a bit.

 

[Kiwi_ME]

Since the traction battery is isolated from any loads when parked by relays on both + and - terminals you’re only suffering internal losses while those remain open, and by all accounts that is surprisingly low.

But all EVs that I’m aware of charge the 12V (or Tesla’s 16V) auxiliary battery on a schedule and in Tesla’s case also when the tiny LFE-technology auxiliary batteries internal BMS requests a charge. That option by the way is a major reason why they took that route.

So, you’re subject to at minimum the overhead losses of 12/16V charging in all cases plus any energy the auxiliary battery actually needs, plus whatever you use specifically in a Tesla with the parking camera system.

In the latter case my understanding is that the traction battery is online full time during operation due to the significant power draw.

 

[Ws6]

Im surprised there arent many responses to the OP. I guess not too many people in here have their EVs sit a long time without a charge or being connected.
Its a good question, lets say you leave your car in long term parking at the airport with 65% charge. What will it be when you return to your car two weeks later?

65% probably. I let my GT sit for 3 weeks at 80%. It was 81% when I next drove it, as the weather had warmed.

 

[Torrid]

Im surprised there arent many responses to the OP. I guess not too many people in here have their EVs sit a long time without a charge or being connected.
Its a good question, lets say you leave your car in long term parking at the airport with 65% charge. What will it be when you return to your car two weeks later?

I don’t think ours has went a day without being driven. It’s the default short trip choice and probably why I’ve never had an opportunity to check extended drain. The GTI sat for a week while I was on vacation, but I drove the Tesla daily.