Using Storage Mode every day

[Palpatine]

I am thinking of trying a new strategy on recharging with the goal of being more gentle on the battery pack long term. I wanted to describe my strategy here and get the input of others.

I recall reading that the voltage levels of the cells is as follows:

Maximum for the cells = 4.2 volts
Range Mode when fully charged = 4.15 volts
Standard Mode when fully charged = 4.10 volts

The best long term healthy percentage is about 50% and keeping the Tesla Roadster in Storage Mode.

I typically drive less than 50 miles per day so I rarely get down to 50% on my battery pack. Normally between 75% and 100% for Standard Mode. I am normally operating between 140-192 Ideal Miles.

The past two days after parking in my garage, I have set the car in Storage Mode each time. I no longer bother to recharge until I am below 100 ideal miles.

When I do recharge, I don't take it up to full Standard at 190-192 ideal miles. I will stop around 150 ideal miles. The only time I plan to charge to full Standard is if I know my day will require it. It is easy enough to get that extra 40 miles into the car quickly.

The goal will be to keep the battery pack mostly between 50% to 75% Standard. 90-150 ideal miles. I believe that this is a better long term strategy for maintaining the battery pack.

Any thoughts?

 

[bolosky]

The goal will be to keep the battery pack mostly between 50% to 75% Standard. 90-150 ideal miles. I believe that this is a better long term strategy for maintaining the battery pack.

Any thoughts?

Carl Medlock (Seattle service manager) commented to me once that the Tesla engineers told him that he should charge the cars he has in for service to a full RANGE MODE charge. Carl said that the engineers told him that while it's bad to do it too much, it's also not good never to do it, and they're finding that most people never/rarely use range mode.

That said, he also didn't do that to my car when he had it last week, so who knows.

 

[dwegmull]

I've been thinking of trying the same strategy as my daily driving is right between 30 and 40 miles. I'm just afraid I would forget to switch back to normal on Friday night as I tend to drive more on Saturdays, often as the result of spur of the moment decisions... I'd hate to be forced back to my dino-car because of an oversight!
Keeping the battery around its mid-charge point is the best way to increase its life span. I've been trying to do something similar with my laptop and cell phone but I've had little success as these devices do not have a way to automatically stop the charge at mid-point. I hear some newer laptops allow the user to set the maximum charge to increase the battery life.
Of course this all theoretical as my car is still in the shop following an unplanned encounter with a fence.

 

[dwegmull]

Carl Medlock (Seattle service manager) commented to me once that the Tesla engineers told him that he should charge the cars he has in for service to a full RANGE MODE charge. Carl said that the engineers told him that while it's bad to do it too much, it's also not good never to do it, and they're finding that most people never/rarely use range mode.

That said, he also didn't do that to my car when he had it last week, so who knows.

I wonder if this is to calibrate the charge level monitoring software. On laptops and cell phones, the software keeps track of how much energy is fed into the battery while charging and then monitors how much is consumed (either directly via a "power meter" circuit and a timer or indirectly by knowing how much energy each subsystem consumes). This technique is often called "Coulomb counting". Over time, especially if using the indirect method, the software and the battery get a little bit out of sync and doing a near full discharge followed by a full charge, resets the software. The lack of synchronization comes from imprecisions in the power consumption model and even more so the variations in aging from one battery pack to the next. I'm not sure if this method applies to the Roadster, maybe Tesla could confirm...

Greetings,
David

 

[Palpatine]

I could see the value of occassionally doing a full range charge. But how often? Once every six months? I have only done it three times since July 2009.

With my current strategy, I plan on doing a full Standard charge about once per week. Probably on weekends. Other than that, I will try to stay between 50%-75% (90-150 ideal miles).

I wish Tesla would get us an official recommendation for how often we should do a full Range Mode charge to maximum. Does this chemistry of lithium need a full charge, then a deep discharge occassionally?

 

[dwegmull]

I wish Tesla would get us an official recommendation for how often we should do a full Range Mode charge to maximum. Does this chemistry of lithium need a full charge, then a deep discharge occassionally?

I don't think the battery itself "needs" an occasional complete cycle. At least Li-Ion batteries used in consumer electronics products don't. The only reason for a potential need would be to reset and re-calibrate the "fuel gauge".

An official word from Tesla would settle the discussion and stop rumors...

Greetings,
David

 

[tennis_trs]

Has anyone seen any quantitative estimates from Tesla on differences in battery longevity for the different charging modes?

I would think that they would have some idea of the differences since they bothered programming the various modes, and knowing an estimate would help decide whether it is worthwhile bothering with the various modes. I.e., if there was less than a 10% difference in battery life between standard (or storage) and range mode, then I'd probably just always charging in range mode.

 

[tennis_trs]

I wish Tesla would have the charge mode stay as what you set it instead of reverting back to standard mode. I have had a few days in a row where I've needed range mode charges and I can see that if you needed/decided to charge in range or storage mode (and still drove) for several days in a row that it would get annoying to have to remember each time.

 

[Palpatine]

if there was less than a 10% difference in battery life between standard (or storage) and range mode, then I'd probably just always charging in range mode.

I think it is much worse than that. Always charging to 100% in Range mode, and allowing your Roadster to sit all night with a maximum charge, would be extreme. When operating at the extreme limits, the decline in performance over time will likely be greater. Perhaps 2-3 years instead of 7 years. I cannot say for sure, but I don't think the decline would be steady on a graph. It will likely look like it is going over a cliff.

 

[dwegmull]

Has anyone seen any quantitative estimates from Tesla on differences in battery longevity for the different charging modes?

I would think that they would have some idea of the differences since they bothered programming the various modes, and knowing an estimate would help decide whether it is worthwhile bothering with the various modes. I.e., if there was less than a 10% difference in battery life between standard (or storage) and range mode, then I'd probably just always charging in range mode.

My own knowledge is based, in part, from this article (I have other sources that corroborate it but they are not public):
Lithium-ion battery - Wikipedia, the free encyclopedia

Relevant extract:
At a 100% charge level, a typical Li-ion laptop battery that is full most of the time at 25 °C or 77 °F will irreversibly lose approximately 20% capacity per year. However, a battery in a poorly ventilated laptop may be subject to a prolonged exposure to much higher temperatures, which will significantly shorten its life. Different storage temperatures produce different loss results: 6% loss at 0 °C (32 °F), 20% at 25 °C (77 °F), and 35% at 40 °C (104 °F). When stored at 40%–60% charge level, the capacity loss is reduced to 2%, 4%, 15% at 0, 25 and 40 degrees Celsius respectively

Greetings,
David

 

[stopcrazypp]

I wonder if this is to calibrate the charge level monitoring software.

That's what I was about to say too. In consumer products at least, the only reason to cycle the charge level in li-ion is to calibrate the software. There isn't any memory effects like in NiCd batteries, so there shouldn't be a chemistry related reason to do this cycling.

 

[tennis_trs]

My own knowledge is based, in part, from this article (I have other sources that corroborate it but they are not public):
Lithium-ion battery - Wikipedia, the free encyclopedia

Relevant extract:
At a 100% charge level, a typical Li-ion laptop battery that is full most of the time at 25 °C or 77 °F will irreversibly lose approximately 20% capacity per year. However, a battery in a poorly ventilated laptop may be subject to a prolonged exposure to much higher temperatures, which will significantly shorten its life. Different storage temperatures produce different loss results: 6% loss at 0 °C (32 °F), 20% at 25 °C (77 °F), and 35% at 40 °C (104 °F). When stored at 40%–60% charge level, the capacity loss is reduced to 2%, 4%, 15% at 0, 25 and 40 degrees Celsius respectively

Greetings,
David

Information similar to this and more is the type of information which would be useful from Tesla, based on their testing and estimates, to help owners try to make their batteries last longer and have an idea of how much difference various changes might make.

 

[Palpatine]

In consumer products at least, the only reason to cycle the charge level in li-ion is to calibrate the software. There isn't any memory effects like in NiCd batteries, so there shouldn't be a chemistry related reason to do this cycling.

So it would only be to make your software more accurate. And at the same time we would be damaging our batteries a little bit to make the software more accurate?

I am not going to charge in Range mode just for the software. I think I am likely to use Range mode at least two times per year just in regular use. I can live with it if the software is a bit off in the estimate of remaining miles.

 

[Palpatine]

Relevant extract:

At a 100% charge level, a typical Li-ion laptop battery that is full most of the time at 25 °C or 77 °F will irreversibly lose approximately 20% capacity per year.

When stored at 40%–60% charge level, the capacity loss is reduced to 2%, 4%, 15% at 0, 25 and 40 degrees Celsius respectively

That would appear to confirm the strategy that I am trying to follow.
With temperatures typically less than 25 Celsius, the loss in capacity should be minimal. Especially with all of the extra battery management technology that Tesla has installed.

My battery pack right now is at 140 ideal miles and was in my garage all night, at that charge level, in Storage mode. How many hours per day is your Roadster just sitting in your garage waiting for you? More than 12? More than 18? Not a daily driver and waiting more than 48 hours?

Imagine all of that time spent in your garage fully charged up and wearing down the cells.

For me, I typically know in advance from my calendar if I am going to be driving 100 miles in a day. So there is plenty of time to bring the car up to a higher charge level (190 ideal miles) if I need to.

 

[ChargeIt!]

James:

How many hours per day is your Roadster just sitting in your garage waiting for you? More than 12? More than 18? Not a daily driver and waiting more than 48 hours?

Imagine all of that time spent in your garage fully charged up and wearing down the cells.

Good point ! And I agree.

On another note: There have been discussion elsewhere of what level or pecent S.O.C. the STO mode allows the battery to discharge to naturally (just sitting), and the unofficial estimates (and first- and second-hand info from Tesla) vary widely. And the opposite comes into question too, i.e. once charging is triggered, what % SOC does the BMS charge the battery to? I am curious specifically about the latter. How about "exhausting" your batteries to, for example, the mid-twenties in miles IR, then plug in and reporting the % SOC and miles IR at the end of the charging process ?

 

[bolosky]

Relevant extract:
At a 100% charge level, a typical Li-ion laptop battery that is full most of the time at 25 °C or 77 °F will irreversibly lose approximately 20% capacity per year. However, a battery in a poorly ventilated laptop may be subject to a prolonged exposure to much higher temperatures, which will significantly shorten its life. Different storage temperatures produce different loss results: 6% loss at 0 °C (32 °F), 20% at 25 °C (77 °F), and 35% at 40 °C (104 °F). When stored at 40%–60% charge level, the capacity loss is reduced to 2%, 4%, 15% at 0, 25 and 40 degrees Celsius respectively

The Roadster will never charge the cells to what the battery manufacturers consider to be 100%, which is 4.2V for these cells. Instead, they charge up to 4.15V (which is about 90% of the batteries' charge capacity; charge isn't linear in voltage) when in range mode, and about 90% of that (4.10V) in standard mode. So, a standard mode charge is already only ~80% of the cells' capacity.

This means that we're a little farther down the curve than you'd think from the above quote, and the amount of additional life that you'll get from the storage mode trick will be smaller. It'll probably still help some, though.

 

[donauker]

The Roadster will never charge the cells to what the battery manufacturers consider to be 100%, which is 4.2V for these cells. Instead, they charge up to 4.15V (which is about 90% of the batteries' charge capacity; charge isn't linear in voltage) when in range mode, and about 90% of that (4.10V) in standard mode. So, a standard mode charge is already only ~80% of the cells' capacity.

According to this Tesla Blog entry the 4.15V charge level of Range Mode equals 95% SOC and the 4.10V Standard Mode equals 90% SOC.

1.Avoiding very high and very low states of charge. Voltages over 4.15V/cell (about 95 percent state of charge [SOC]) and voltages below 3.00V/cell (about 2 percent SOC) cause more stress on the insides of the cell (both physical and electrical).

This is a second reason why we have limited our maximum state of charge to 4.15V/cell instead of 4.2V/cell. We also offer the driver the option of charging to only 3.8V/cell (~50 percent) or 4.10V/cell (~90 percent) to further extend calendar life if the full vehicle range is not needed on the next few trips. We advise and encourage a full (4.15V/cell) charge only when it is needed.

Standard Mode will in addition not use the lower 10% of the battery thus using approximately the middle 80% range. 90% SOC to 10% SOC

 

[DrTaras]

Nearly 1.5 years with a Roadster and although I've been out of town before, I never used Storage mode until my recent 2 weeks away. Started with a full SOC & when I returned it said I had only 35 miles. Is that what is supposed to happen?

 

[mpt]

I left with ~25% SOC, put it into Storage mode and on return three weeks later it was about the same. Odd thing was, I switched to Standard and left it to charge, following morning the 'Finish' LED colour was green and I had the regen light on despite regen being ok. Charge level looked to be about 95% of a full range charge and the regen error condition had cleared by the evening return home.

Odd.

 

[vfx]

I'd swear sometimes the regen is less robust (if only fractionally) after Standard charge sometimes. When I leave home it's downhill so I'm in it right away. This does not seem to last for a long time.