Lithium Ion batteries may last much longer than we're lead to believe

I end up charging in the morning before I leave to warm the battery so it ends up sitting overnight quite often hovering somewhere around 40-70%. The phone app is a nice way to control the charging.

yobigd20 said:

If that is all really true, I would like to to see an option in my Model S to have a "max battery charge" capacity were I can set it to 60-70% instead of the "standard charge" that is 90%. I don't need 241 miles daily. I only need about 100 miles max for daily usage. I'd rather have my daily drive go from 70%-30% than 90% to 50% if that maximizes battery life.

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100% on the dash isn't 100% of the cell. I would imagine that a standard charge of the Tesla battery is pretty close to ~80% of the full cell capacity. And at least in the 'healthy' range of charge level for those cells.

I think fast charging degradation is mostly due to heat build up also. So active cooling will probably help a lot.

100thMonkey said:

I end up charging in the morning before I leave to warm the battery so it ends up sitting overnight quite often hovering somewhere around 40-70%. The phone app is a nice way to control the charging.

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I do something similar- I schedule the charge so it just finishes replenishing the range used on the previous day's commute about the time I usually leave for work in the morning.

I've heard roadster owners talk about a "storage mode" that keeps the battery at a lower state of charge than a standard charge. I have no idea if they didn't include this in the Model S because it didn't really help that much or if they were worried about confusing owners with too many charging options.

It would also nice to have an option to have the active cooling keep the battery nice and cool whenever the car is plugged in, not just when it is actively charging. I'd be willing to pay a little more on my electric bill to improve battery life!

wraithnot said:

...I've heard roadster owners talk about a "storage mode" that keeps the battery at a lower state of charge than a standard charge. I have no idea if they didn't include this in the Model S because it didn't really help that much or if they were worried about confusing owners with too many charging options....

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my guess is that the bad press from the few bricking incidences with the Roadster had them rethink the BMS interface. they probably figured it was safer to just get rid of the storage mode so that it was crystal clear that it was never recommended to leave the car for long periods unplugged.

I do wish there was a 50% default option, this way I could come home, have it automatically top up to 50% and then rely on the charging timer or phone app top up by the time I needed to leave the next day to whatever level I needed for that day's driving to have me back at the stables with no less than 20% and more often closer to 50%. There would be days where a 50% charge with no topping up would be plenty. perhaps something like a 60% default would be even better, always having a little extra. I'm one of those folks who both wants to take advantage of the cold ambient storage effect as well as have the battery warmed right before use, all with the hopes of still using the same batteries 15 years from now.

ElSupreme said:

100% on the dash isn't 100% of the cell. I would imagine that a standard charge of the Tesla battery is pretty close to ~80% of the full cell capacity. And at least in the 'healthy' range of charge level for those cells.

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It would be nice to know just what standard and range charge is.

4.2 volts per Li cell seems to be the industry standard maximum. The Nissan LEAF has two charge settings. 100% charge is 4.1 volts per cell, and their recommended 80% charge is a bit over 4 volts per cell. Wonder why Tesla will not tell us what voltage they really charge to. We can't do anything about it, but I'd like to know.

As to heat being detrimental, LEAF owners in AZ and TX can attest to that - the LEAF has no battery temperature management system.

Doug_G said:

Yeah, this was the first winter where I actually let my Roadster drop to 20% in Storage Mode. Previously I've had it out a few times during the winter and never had it all the way down. I was definitely a little nervous about it sitting at 20% and topping a little each night. That might very well provide optimum battery preservation, but what happens if there is an extended power outage? Maybe Tesla figured the extra complexity wasn't worth the risk - also perhaps with the different chemistry the charge level is less important than other parameters such as temperature.

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I believe Tesla was claiming that Model S could be left sitting for half a year unplugged without risk of bricking... But that was IIRC moths before they actually started production.

Zzzz... said:

I believe Tesla was claiming that Model S could be left sitting for half a year unplugged without risk of bricking... But that was IIRC months before they actually started production.

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September 2012:

ms_owners_guide.pdf said:

Discharging the Battery to 0% may permanently damage the Battery. To
protect against a complete discharge, the Model S enters a low-power
consumption mode when the charge level drops to 5%. In this mode, the
Battery stops supporting the onboard electronics to slow the discharge rate
to approximately 4% per month. Once this low-power consumption mode
is active, it’s important to plug in the Model S within two months to avoid
Battery damage.

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brianman said:

September 2012:

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Yeah, they lowered it

I was reffiring to this claim:

"For example, a Model S battery parked with 50 percent charge would approach full discharge only after about 12 months."

It is from Feb 24, 2012. Not even a year passed.

At night and during other times when I'm not using my LEAF, I try to park it with around 30-40% SOC. I use a charge timer to bring it up to 60-70% right before I leave the house in the morning, basically by setting an 80% timer and unplugging early. Once the Model S supports charging timers, I imagine it would be a good idea to do something similar in order to maximize battery life. If/when I eventually purchase a used Model S at a discount, I expect I will try to keep the SOC in the 25-50% range most of the time, which should be more than adequate for typical daily driving.

I just left the Rav4 EV gen II sitting for 3 weeks unplugged at about 50% SOC. I left the 12 volt battery on a trickle charger, as they tend to die quite quickly in both the Rav4 and the LEAF.

I had originally left the daily climate control timer on, but while I was in Europe, I was able to deactivate it with the EnTunes app on my iPhone. The range had dropped several miles daily until I remembered to turn this off, then stayed the same for the next two weeks (at 61 miles).

It doesn't appear to have the same vampire loads as Model S.

> this was the first winter where I actually let my Roadster drop to 20% in Storage Mode. Previously I've had it out a few times during the winter and never had it all the way down. I was definitely a little nervous about it sitting at 20% and topping a little each night. That might very well provide optimum battery preservation, but what happens if there is an extended power outage? [Doug_G]

2.0 Roadster here just keeps on tickin' during winter conditions:

Last Charge (Std) was on 2013-March 04.
Made a few short trips during this 7 week period.
2013-April 25: 81 miles/88 miles on screens. 13.4vdc.

Does this qualify as an 'extended power outage'??
--

That 'max charging' value would be also good for medium-to-long-term storage + charging. Simply set it to 50% and plug in via fast or slow (110v) charging. It will only charge to 50% then stop, yet vampire charging wouldn't kill it and pack cooling/heating would still be engaged.

The alternative is to go away for many weeks and either sticking at 90% the entire time, or disconnect and risk some sort of other discharge related issue.

I vote strongly for a simple 'percent charge' setting alongside the 'delayed charge' setting...

Zzzz... said:

Yeah, they lowered it

I was reffiring to this claim:

"For example, a Model S battery parked with 50 percent charge would approach full discharge only after about 12 months."

It is from Feb 24, 2012. Not even a year passed.

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They are talking about different conditions. One, where the Model S is left unplugged at 50% SOC, it could sit for about 12 months. The other, when the car is left at 5% SOC it can sit for two months.

I was looking for this thread the other day and couldn't find it. Glad it got bumped.

Additional recent public statement of interest:

Except in the cases of a collision, opening of the battery pack by non-Tesla personnel or intentional abuse (lighting the pack on fire with a blowtorch is not covered!), all damage is covered by warranty, including improper maintenance or unintentionally leaving the pack at a low state of charge for years on end.

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Creating the World's Best Service and Warranty Program | Blog | Tesla Motors

Perhaps I'm misreading but when I hear "years" I think "at least 24 months".

brianman said:

I was looking for this thread the other day and couldn't find it. Glad it got bumped.

Additional recent public statement of interest:

Creating the World's Best Service and Warranty Program | Blog | Tesla Motors

Perhaps I'm misreading but when I hear "years" I think "at least 24 months".

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Yes, that was my reading. Clearly seemed to be addressing the "bricking" controversy, and I believe that Jalopnik mentioned something to that effect in their writeup (in a positive way, I might add). The only caveat in the statement is the word "unintentionally." So saying you planned to leave it unplugged for years at a time might be a bad idea.

It is my understanding that the bad way to age the battery quickly is to overheat it near 100% state of charge.
So DC quick charging to 100% on a really hot day is probably not a good practice.
This is likely true for vehicles like the Nissan LEAF as well.

I charge to 80% every night (on a timer to finish right before I leave), then I drive to work bringing it down to 50% where it sits all day before I head home.
I feel good about leaving it at 50% SoC during the heat of the mid-day, rather than trying to top it back up with at work charging.