Do you know that you must keep your battery charged?

[richkae]

I'm imaging a meeting with a bunch of lawyers, risk analysts and engineers.
The engineers are saying "they should be totally safe, the chance of cascade failure and fire is very small."
The lawyers/risk analysts say: "you want to bet the company on that?"
Engineers: "if we keep the coolant circulating and the monitoring on until the batteries are completely dead that is the very best thing we can do to minimize risk"
Lawyers: "Good - do that."
Engineers: "If someone leaves their car unplugged for too long, they will brick the battery and need a replacement."
Lawyers: "That's bad - dont do that."
Engineers: "You cant have it both ways. Which one do you want?"
Lawyers: "Better a brick than a fire every time."
Engineers: "OK"

 

[strider]

My casual attempt to make the LEAF pack last as long as (I think is) possible involves setting charge timers to only charge to 80% right before I need to leave on my commute, then leave the car all day at ~50% SOC (no at office charging opportunities), then back home at night and on trickle charge to be ready for the next morning.
I think/hope I am doing right by the pack by keeping the average SOC at ~50%, and trying to get it away from the extremes as soon as I can.

Not sure how the LEAF handles this but on a Roadster I believe this behavior would cause the cells to go out of balance over time. As I understand balancing happens after charing is completed. So doing a partial charge and immediately driving would not allow the pack to balance itself. So then the question is, which is worse for pack longevity? A pack left at higher SOC or one that is out of balance?

 

[ElSupreme]

I'm imaging a meeting with a bunch of lawyers, risk analysts and engineers.
The engineers are saying "they should be totally safe, the chance of cascade failure and fire is very small."
The lawyers/risk analysts say: "you want to bet the company on that?"
Engineers: "if we keep the coolant circulating and the monitoring on until the batteries are completely dead that is the very best thing we can do to minimize risk"
Lawyers: "Good - do that."
Engineers: "If someone leaves their car unplugged for too long, they will brick the battery and need a replacement."
Lawyers: "That's bad - dont do that."
Engineers: "You cant have it both ways. Which one do you want?"
Lawyers: "Better a brick than a fire every time."
Engineers: "OK"

A lot of times Engineers have this debate with one another, or with themselves!

 

[TEG]

Not sure how the LEAF handles this but on a Roadster I believe this behavior would cause the cells to go out of balance over time. As I understand balancing happens after charing is completed. So doing a partial charge and immediately driving would not allow the pack to balance itself. So then the question is, which is worse for pack longevity? A pack left at higher SOC or one that is out of balance?

Yes, but "out of balance" (I think) can be corrected on the next full charge cycle that is given enough time.
Once and a while I have to take the LEAF on longer trips, and I will bypass the normal charge timers and let it go to 100%.
I don't do this very often, but it at least a chance to do a "balancing act" occasionally which may be enough.
In any case, my range seems the same as it was when new 10 months and 9,000 miles ago.

 

[markwj]

A laptop can sit, shut off, with no battery management or cooling, without risk. An EV should be able to do the same, and I think now the newer Tesla design allows this to happen instead of managing the cells to death.

A typical laptop battery lasts 1 to 2 years of moderate-to-heavy use, if you're lucky. I don't want an EV that gives me a battery with a similar lifetime. Period.

The difference is that the Tesla batteries are conditioned (coddled, pampered, whatever) and that takes power.

If the ambient temperature is 20 celcius, what you say may be partially correct, so long as there is no issue with the battery (cell going bad, coolant leak, short circuit, etc). But, it is 33 celcius in the shade, for the majority of the year, where I live, and that will cook a battery without conditioning.

From what I can see, the battery management on my Roadster 2.5 works just fine. There is a vampire drain, but it seems acceptable and not at all excessive to me, and simply leaving the car plugged in resolves all concerns and lets the battery management system do what it does best.

 

[TEG]

I'm imaging a meeting ...

Yeah, I had been thinking the same thing - the "active thermal management" could be left on for safety reasons sometimes even if it means running out of charge sooner.
One problem is that the algorithms have no way of knowing how long it will be until the vehicle gets plugged in next time. They probably assume it will be relatively soon as that is by far the most common scenario.

 

[JRP3]

Everyone is sort of missing my point. Laptops are not bursting into flames when abused and neglected. Yes cells last longer if sitting around 50% SOC or lower, but not too low, yes they last longer if not allowed to get too warm. But they won't last if they are "managed" till all their power is drained. As I mentioned previously I have an older GPS with a single 18650 LiCo cell. The cell sat for about three years with no management in my fridge, it has now been in use sitting on my dashboard, for at least two years, sometimes baking in the sun, sometimes unused for 3-4 months, with no active management. Most of the time it is not plugged in. Basically it has been used in ways that would kill a Roadster pack many times over. So what is the difference? No active management. Obviously active management is good if you have the power to supply it, i.e. when plugged in or with a high enough SOC to power itself. I think the early pack management setup that Tesla used was too aggressive, and I think Tesla agreed since they changed it to be less so.

 

[dsm363]

I understand where you are coming from but how should Tesla handle any heat damage once the pack was discharged to the point where thermal management stops? While they may save the battery, any damage might drop the range so low that they would have to replace to battery pack under warranty.

 

[strider]

Everyone is sort of missing my point. Laptops are not bursting into flames when abused and neglected.

Ah, you meant risk of fire, not risk of bricking. My apologies.

 

[markwj]

Everyone is sort of missing my point. Laptops are not bursting into flames when abused and neglected. Yes cells last longer if sitting around 50% SOC or lower, but not too low, yes they last longer if not allowed to get too warm. But they won't last if they are "managed" till all their power is drained.

I get your point. I disagree, but I do understand and appreciate your point of view.

As I mentioned previously I have an older GPS with a single 18650 LiCo cell. The cell sat for about three years with no management in my fridge

Clearly you managed it. You put it in a conditioned environment, to keep the temperature in an good range to extend its lifetime. Sure, electricity from the cell, or neighbouring cells, was not used, but your fridge was plugged into the wall. No practical difference to Tesla's active thermal management. If you had left it at room temperature, or out in the hot sun, would the state of the cell be the same after three years? I doubt it - and so do you (otherwise you wouldn't have stored it in the conditioned environment of the fridge).

, it has now been in use sitting on my dashboard, for at least two years, sometimes baking in the sun, sometimes unused for 3-4 months, with no active management. Most of the time it is not plugged in.

Yep. My GPS has the same cell. It lasted me almost 3 years and then I had to replace it. 3 years. If the same cells in my roadster die after 3 years, I'll be pissed.

I think the early pack management setup that Tesla used was too aggressive, and I think Tesla agreed since they changed it to be less so.

I think they erred on the side of safety and battery longevity. For where they were when the roadster was produced, I think they made the right decision - and the age and condition of the vast majority of roadster batteries (even those dating back to 2008) are showing this. For the Model S, they have taken 4 years of Roadster experience, and engineered some solutions with (presumably) less vampire drains. How much of that is due to engineering changes, and how much to lower power electronics, I doubt we'll ever know.

 

[JRP3]

Fair point about my "fridge management", though there was no charging going on to keep SOC up. Remember, I've never said Tesla should not actively manage the cells, I've just been saying that after some point of very low SOC without being plugged in, management needs to stop to keep the cell from further discharge, which is what Tesla is now doing. Extended time in the heat may damage a cell/pack, extended time at zero SOC will damage it.

 

[dsm363]

Fair point about my "fridge management", though there was no charging going on to keep SOC up. Remember, I've never said Tesla should not actively manage the cells, I've just been saying that after some point of very low SOC without being plugged in, management needs to stop to keep the cell from further discharge, which is what Tesla is now doing. Extended time in the heat may damage a cell/pack, extended time at zero SOC will damage it.

I agree with you but Tesla would have to clearly define when their responsibility under warranty ends though. They shouldn't be responsible for someone who thermally damaged their pack because they didn't plug in for an extended time after a zero SOC.

 

[Norbert]

I think they erred on the side of safety and battery longevity. For where they were when the roadster was produced, I think they made the right decision - and the age and condition of the vast majority of roadster batteries (even those dating back to 2008) are showing this. For the Model S, they have taken 4 years of Roadster experience, and engineered some solutions with (presumably) less vampire drains. How much of that is due to engineering changes, and how much to lower power electronics, I doubt we'll ever know.

And how much is due to chemistry changes. (Or maybe next week they issue a firmware update.) It may simply be that the older batteries didn't do that much better at 1%, 2% or even 4% than at 0%, when sitting around for a longer time especially without thermal management. So you might have a half-damaged pack for 4 weeks instead of a fine one for one week, and they decided a fine one for one week is better since if the owner doesn't come within 11 weeks, he might not come within 15 weeks either, and they might have further thought it to be better to completely save 5 battery packs, than to end up with 10 packs that are half-damaged and most of those then need to be replaced still.

 

[richkae]

Experiences with single cells over the long term are good.
But, suppose that 1 in 100 million cells has a construction flaw that can cause thermal runaway if not managed.
That becomes 1 in 15000 cars.
A single cell failing and getting hot might not be a big deal. A single cell in 6 ( laptop battery ) might also be unlikely to cause a problem. A single cell surrounded by hundreds dramatically increases the chance of one bad cell affecting others.

Tesla has more information than we do. They may have been conservative. I won't doubt their choices without more information.

 

[DrTaras]

Did you have to sign the document at purchase which described the consequences of not plugging in?

Not my 1st one

 

[DrTaras]

That said, the information I provided in the article is accurate, despite how uncomfortable it may make you feel that someone dares to criticize a Jew.

This statement exudes ANTI-SEMITISM and I don't care if you turn out to be Jewish.
Your "facts" still do not corroborate a leap that he's working for the Mossad no more than he is working for the KGB (maybe his grandparents were Russian) or even for the USA under the Patriot act; conjecture, counselor.
Stick to uncovering facts (as you did quite well) and stay out of Fantasyland. Also, sorry for blowing your cover on calling it a class act for leaving his kids out of the fray. My $0.04.

 

[Norbert]

It may simply be that the older batteries didn't do that much better at 1%, 2% or even 4% than at 0%, when sitting around for a longer time especially without thermal management.

Although I meant the above more as a mere possibility, to balance other possibilities, I'd like to back it up a little to show that the letter is not as clear in one direction as some may still think :

On page 2, the letter states:

The fact that your battery pack only deteriorated to 0% in 42 days when parked with a charge level of 21% [...]

One could read this as a mere discharge, but "deteriorate" means "to diminish or impair in quality". This suggests (though perhaps the author was not aware of conveying this meaning) that even above 0%, the quality of the pack may already diminish (and that therefore perhaps it might not be a great thing to make it stay in that state for an even longer time, by changing firmware).

The letter also states on page 2:

With a fully charged battery pack it would last many months before the 4% threshold and subsequent alarms would be reached.

This suggests, again perhaps not by conscious choice of the author, that the "threshold" is not identical with the alarms, but something else, that there is more to it. The alarms are something that happens "subsequently".

So I think if one reads it all carefully and looks at what the letter actually says, it does not easily support specific interpretations about how it works and how it could be improved. The only clear import is that the Roadster's battery lasted for the durations described in the manual, and actually did better than that.

 

[markwj]

Or maybe next week they issue a firmware update.

That, I doubt. I'd bet money against it. Issuing a firmware update to 'fix' this would be tantamount to an admission there was a problem to be fixed, and a liability nightmare.

 

[markwj]

It really would be fascinating to know the real facts for this, and the vehicle logs would show us.

From my reading, the only thing Tesla has clearly said is that the drain behaves differently above 50% SOC than below. Even that is not clear if the difference is battery chemistry or battery management behavior.

Has anyone left their roadster unplugged and not charged for months (ideally starting with SOC more than 50% and ending with less)? Anyone willing to send me/us vehicle logs of this to see what happened to the SOC over time? At 5% a week, we'd need more than 2 months to get a reasonable idea of what is going on.

 

[benji4]

That, I doubt. I'd bet money against it. Issuing a firmware update to 'fix' this would be tantamount to an admission there was a problem to be fixed, and a liability nightmare.

That's a pretty scary thought... if that was the way the world worked nobody would ever fix anything that was broken simply because they'd be afraid of being sued for admitting their error. If fixing the problem gives them legal issues, can you imagine how bad things would be on them if it came out later that the problem was covered up just so they could avoid acknowledging there was a problem in the first place and more cars ended up getting bricked in the meantime? (actually on second thought....sounds like Toyota!)