Charge loss

[westcoast]

AFAIK, the lower end is not detrimental to battery longevity, but it does leave you with very little range left, less battery power (because of lower voltage) and higher risk of under-voltage/bricking. The situation is similar for low temperatures (there is less apparent capacity/power during operation, but no real battery longevity affects).

The reason to minimize the time spent in high SOC is because it promotes oxidation (same with high temperatures), which means quicker degradation of the battery cell. That's why storage mode in the Roadster is 50% SOC.

According to Wikipedia, a laptop cell stored at 100% SOC loses 20% capacity in a year at 25 degrees C. Stored at 40-60%, that reduces five-fold to 4%/year.
Supposedly some chemistries like LiFePO4 are not affected by being stored at high SOC.
Lithium-ion battery - Wikipedia, the free encyclopedia

So what is optimal charging in the case of a lightly used car? I.e. It's used daily but only say 20 miles a day?

A. Keep it plugged in all the time, so it's sitting at full charge almost all the time

B. Charge it fully, but only plug it in when it reaches 20 percent, which might be once every 4 days

C. Or something else? Maybe keep it in storage mode and charge it daily at storage mode?

 

[bonnie]

So what is optimal charging in the case of a lightly used car? I.e. It's used daily but only say 20 miles a day?

A. Keep it plugged in all the time, so it's sitting at full charge almost all the time

B. Charge it fully, but only plug it in when it reaches 20 percent, which might be once every 4 days

C. Or something else? Maybe keep it in storage mode and charge it daily at storage mode?

Leave it plugged in all the time, but have it set so it only charges to 80% SOC.

 

[dsm363]

So what is optimal charging in the case of a lightly used car? I.e. It's used daily but only say 20 miles a day?

A. Keep it plugged in all the time, so it's sitting at full charge almost all the time

B. Charge it fully, but only plug it in when it reaches 20 percent, which might be once every 4 days

C. Or something else? Maybe keep it in storage mode and charge it daily at storage mode?

Charge it in standard mode and keep it plugged in when not at use in your garage is what Tesla recommends. They've put a lot of work into this so while it might be possible to out-think their engineers and come up with a strategy that would be easier on the battery over a 10 year period, I'd bet it's such a small change over that time that it's not worth the effort. Easier to just plug your car in and enjoy it. Of course you can leave it unplugged when you're at work or on vacation (car at the airport with a sufficient charge in reserve). Storage mode really is for storage (you are not supposed to drive in it).

 

[ckessel]

Has it been confirmed if the model S has range/standard modes or did they just have "standard" only so that a full battery isn't really completely full and thus not detrimental to battery life?

 

[Lloyd]

My take on this is: tesla is still deciding on how much 'new stuff' to give to a whole new group of owners. I asked if they had completed their training video for the new owners. I was told that most segments have been completed, but some are still in flux. To me this says that some software changes and features are still being decided on.

Tesla understands that the next group of owners may not be as tech savvy as the Roadster group. I asked if model S owners were going to be able to understand different charging modes vs driving modes.... Ie range, standard, performance as well as storage. The answer was they were trying to simplify, and they were still evaluating the ability of the new owners.

 

[brianman]

@Lloyd - In the software industry, this has typically been addressed with "basic mode with smart defaults" and "advanced mode with lots of knobs to adjust". In the word of consumer electronics, it's "quick start guide" vs. "the owner's manual". As a software-heavy consumer product, they should be able to leverage aspects of both approaches without having to fret much.