Storage Mode

[Doug_G]

Okay, my car seems to be maintaining itself at approximately 50 km ideal (ignoring range reserve). Looks like it might be topping up nightly, just a little bit. That might perhaps not be the most efficient way to do things, since if it's cold it would have to warm the pack first.

This is the first time I've had my Roadster parked for the whole winter. In previous years I've had it out occasionally for one reason or another, so it never really bottomed out in Storage mode.

 

[wiztecy]

Whenever I put my Roadster in Storage mode I ensure it stays at 90-110 Miles or 50%-60% Capacity. Lithium Packs are best at 50% SOC. If I'm away and seeing the pack dropping any lower I'll initiate a charge to bring it back up to that range. I'm curious why the Roadster's Charge management would allow the pack to drop so low...

Even when I'm not in Storage Mode and in my daily/weekly use I try to target that number as well after my end of the day use.

 

[djp]

Whenever I put my Roadster in Storage mode I ensure it stays at 90-110 Miles or 50%-60% Capacity. Lithium Packs are best at 50% SOC. If I'm away and seeing the pack dropping any lower I'll initiate a charge to bring it back up to that range. I'm curious why the Roadster's Charge management would allow the pack to drop so low....

Long term storage at close to zero SOC is better for battery life than storage at 50-60%, as this graph from the Long Term Battery Care thread shows. I think the rule of thumb to store at 50% SOC is to allow for self-discharge if the battery is sitting on a shelf for a couple of years. With the Roadster BMS maintaining the SOC there's no risk of over-discharge so it can hold the SOC at a lower level for longer life.

In general, keeping the battery in a cool place at a low SOC is the best way to extend its life.

Long Term Battery Care and Charging Habits - Page 6

 

[Doug_G]

Per djp, Tesla knows best about what to do in Storage mode.

As for daily usage, I don't agree about keeping it at 50%. It may be less stressful in storage, but driving at lower SOC is more stressful on the pack because it has to draw more current to achieve the same power.

 

[djp]

As for daily usage, I don't agree about keeping it at 50%. It may be less stressful in storage, but driving at lower SOC is more stressful on the pack because it has to draw more current to achieve the same power.

I'm running a long term experiment to find out. :smile: I agree punching it to 200kW isn't good at low SOC, but standard city driving should be fine. I'm wagering that the long term effects of high SOC will outweigh the stress of current draw in the 30-50% SOC range. I generally keep the SOC between 30-50% for daily use and top up to a Standard charge on weekends when I'm more likely to have fun with the car.

There's a US Army study that has some supporting data. They found cycling between 0-50% SOC maintained higher battery capacity than cycling 25-75% or 50-100%. They also found that degradation from heat happened faster at higher SOC than lower SOC. In the summer it's better to be at lower SOC.

My three year old Roadster still charges to 300km in Standard Mode - so far so good.

http://www.cerdec.army.mil/directorates/docs/cpi/Cycled_Aged_LiIon_Cells.pdf

During analysis of the data a series of trends stood out. The first being, whenever the cell was held at an elevated temperature both the capacity and power capability of the cell decreased significantly (Figures 3-5). The one notable exception is when the cell was maintained at 0% to 50% state-of-charge (Figure 6).

The second is when the cell was maintained at a high state of charge (Figures 3 and 4). The capacity of these cells faded at an increased rate. This is especially true for the cells maintained at a state-of-charge of 50% to 100%.

View attachment 17564View attachment 17565

 

[Doug_G]

My three year old Roadster still charges to 300km in Standard Mode - so far so good.
View attachment 17564View attachment 17565

Well, okay then, that's pretty good - my three year old Roadster is down 2%. I've got 32,000 km. How much mileage does yours have?

 

[djp]

My mileage is about half of yours. I use it mostly around the city, which is another reason low SOC works for me. Calendar life is a bigger factor than mileage if the car is lightly used. I'd keep it at a higher SOC if I was doing more long range drives or unexpected trips.

 

[Doug_G]

I checked in on my Roadster this morning, and it was saying 38 km (I guess that would be about 76 km in Range mode - about 20% charge). Normally I try to plug in as soon as possible when it's that low!

I have to peek in beside the charge port, since it's inside the car cover. But I think I'll start checking it every day, just to see what it is doing...

 

[Doug_G]

Okay, I figured out what it's doing. Every night it powers up and adds 1 km. It charges up to 38 km. The next day it drains to 37 km. Lather, rinse, repeat.

 

[wycolo]

> Lather, rinse, repeat.

You have the 120 volt charge cord connected all the time and in STORAGE MODE, right?
--

 

[Doug_G]

No, I have the HPC connected and it is in storage mode.

Yesterday it topped to 40 km (plus the hidden ~38 km "range mode" reserve). Seems to be maintaining a 20% charge, topping up nightly.

 

[Pantera Dude]

Storage Mode Question

I want to put my car into storage mode. My "timer" controlled charger only works intermittently. Will putting the car in storage mode run the battery down to a low charge by itself or will it allow the battery to discharge normally until it gets to where it needs to be charged? I don't want to put it in storage mode if it's immediately going to run the battery down, since I can't depend on the timer. At what ideal miles should the charger start up in storage mode?

 

[ViperDoc]

Storage

I want to put my car into storage mode. My "timer" controlled charger only works intermittently. Will putting the car in storage mode run the battery down to a low charge by itself or will it allow the battery to discharge normally until it gets to where it needs to be charged? I don't want to put it in storage mode if it's immediately going to run the battery down, since I can't depend on the timer. At what ideal miles should the charger start up in storage mode?

My understanding is it will allow car to discharge at its own pace and then kick in to keep it at a safe low level. My own recent experience was that I left my car in storage mode at 190 miles and 8 days later it was at about 140 miles of charge—so I think it was still mostly discharging at its own rate.

 

[Doug_G]

It will run down, very gradually, to a very low charge level, and then charge periodically to maintain at least that level. If I recall correctly it was 30 km ideal km (on top of the Range mode reserve). (That's about 20 miles.)

The discharge is due to the processors that have to run to monitor the battery pack.

 

[shrink]

I'm new here and don't even own a Roadster yet, but I've been researching this in anticipation of buying a CPO that I'm not going to drive very much the first few months.

From the Owner's Manual page 5-2:

"Keep in mind that when the vehicle is left unplugged with a full Battery, the initial rate of decline can be significant. When fully charged, the Battery’s charge level can drop as much as 7% a day and 50% within the first week. When the Battery’s charge level falls below 50%, the rate of decline slows down toapproximately 5% per week."

and Page 5-3:

"When you charge the vehicle using the Storage charge setting, the vehicle is automatically kept at a reduced charge level to optimize the life of the individual cells within the Battery."

Does that mean in Storage mode and plugged in, it will discharge to around 50% within about a week and then maintain about a 50% charge?

I'm not sure how well that would work with an intermittently working charging timer.

 

[Smop]

I'm new here and don't even own a Roadster yet, but I've been researching this in anticipation of buying a CPO that I'm not going to drive very much the first few months.

From the Owner's Manual page 5-2:

"Keep in mind that when the vehicle is left unplugged with a full Battery, the initial rate of decline can be significant. When fully charged, the Battery’s charge level can drop as much as 7% a day and 50% within the first week. When the Battery’s charge level falls below 50%, the rate of decline slows down toapproximately 5% per week."

and Page 5-3:

"When you charge the vehicle using the Storage charge setting, the vehicle is automatically kept at a reduced charge level to optimize the life of the individual cells within the Battery."

Does that mean in Storage mode and plugged in, it will discharge to around 50% within about a week and then maintain about a 50% charge?

I'm not sure how well that would work with an intermittently working charging timer.

If the battery needs a charge desperately it will override the onboard charging timer. If not it will wait till the timer parameters are met and charge at this point. I have seen some Roadster's actually bleed more miles in storage mode vs being left unplugged over the same duration of time.

 

[Doug_G]

It goes down to less than 20%. Personally I don't really like that it goes that low. I would prefer a bigger safety margin when the car is likely to be unattended for a long time.

I like the Model S method - there is no official storage mode, but you can lower the slider to 50%.

 

[Pantera Dude]

If the battery needs a charge desperately it will override the onboard charging timer. If not it will wait till the timer parameters are met and charge at this point. I have seen some Roadster's actually bleed more miles in storage mode vs being left unplugged over the same duration of time.

Will it then start charging at about the same time, (within 24 hours), as it would if the timer was working? If so, that is a very cool and smart feature!

Thanks

 

[djp]

Will it then start charging at about the same time, (within 24 hours), as it would if the timer was working? If so, that is a very cool and smart feature!

Thanks

Yes, it always kicks off a charge cycle every 24 hours but doesn't bother to continue charging if it's >20%.

 

[Pantera Dude]

Yes, it always kicks off a charge cycle every 24 hours but doesn't bother to continue charging if it's >20%.

Please don't anybody bite my head off for asking what is probably a redundant question. It sounds like I have nothing to worry about even if my charge timer doesn't work at all? If it is plugged in, I don't have anything to worry about? I just don't want to make a 40 thousand dollar mistake.

Thanks