You might consider charging slower

[scaesare]

Clearly there is much debate about balancing, charge/discharge activity suggestions, etc...

One thing that seems to be universally agreed upon however, is that the two thing Lithium ION cells like are:

-Being at a SOC that's not at one extreme or the other (especially for extended periods)

-Staying cool

My question is: what's "cool"? My garage can get to be 100-110+ in the summer during the day... and even at night when I'm charging can stay 100+. What's the range for a LiON cell to be happiest?

 

[AmpedRealtor]

My question is: what's "cool"? My garage can get to be 100-110+ in the summer during the day... and even at night when I'm charging can stay 100+. What's the range for a LiON cell to be happiest?

This is why you are supposed to keep the Model S plugged-in whenever possible. When the car is plugged-in, the battery's temperature is properly maintained regardless of ambient air temperatures. The same happens when you pre-condition the car using the remote app.

 

[scaesare]

This is why you are supposed to keep the Model S plugged-in whenever possible. When the car is plugged-in, the battery's temperature is properly maintained regardless of ambient air temperatures. The same happens when you pre-condition the car using the remote app.

I've also seen some discussion that simply being connected to shore power doesn't necessarily enable the pack temp management systems... or it may be that there's not solid evidence it's been triggered that anybody has posted.

I know I haven't ever heard my my car automatically spin up the systems to start managing temp even in an awfully hot garage when plugged in. It's ostensibly the same compressor as used for cabin HVAC, so it should certainly be audible...

In any case... I'd be interested in what the "happy" temp range is is surmised to be...

 

[mknox]

I've also seen some discussion that simply being connected to shore power doesn't necessarily enable the pack temp management systems... or it may be that there's not solid evidence it's been triggered that anybody has posted.

I've left mine plugged in for extended periods and have a dedicated meter on my EV circuit. I've only ever seen power drawn to top up vampire losses (5 kWh every other day). Never any evidence of anything other than that.

 

[wraithnot]

Clearly there is much debate about balancing, charge/discharge activity suggestions, etc...

One thing that seems to be universally agreed upon however, is that the two thing Lithium ION cells like are:

-Being at a SOC that's not at one extreme or the other (especially for extended periods)

-Staying cool

My question is: what's "cool"? My garage can get to be 100-110+ in the summer during the day... and even at night when I'm charging can stay 100+. What's the range for a LiON cell to be happiest?

This paper has some relevant info: http://www.nrel.gov/docs/fy12osti/53817.pdf

Check out the bottom panel of figure 1

 

[montgom626]

Batteries are like people

-Staying cool

My question is: what's "cool"? My garage can get to be 100-110+ in the summer during the day... and even at night when I'm charging can stay 100+. What's the range for a LiON cell to be happiest?

Batteries are like people. If you are comfortable, the battery is comfortable. Best temp is around 70 degrees. Too cold or too hot and the battery, just like you, is not comfortable.

 

[jerry33]

This is why you are supposed to keep the Model S plugged-in whenever possible. When the car is plugged-in, the battery's temperature is properly maintained regardless of ambient air temperatures. The same happens when you pre-condition the car using the remote app.

So far there is no evidence that this happens except when charging. I'd be thrilled to learn otherwise.

 

[djp]

2. Why obsess over this issue? The battery you try so hard to 'save' may not be yours for long. Mine was replaced @8000 miles due to circuitry issues.

Four reasons:

1. Battery degradation isn't covered by the warranty.

2. Battery packs cost $40,000 to replace.

3. It's not hard to dial down the charge slider to a level that covers what you normally do in a day, and dial it back up for long trips.

4. The first question asked when a used Roadster comes up for sale in this forum is "What's the condition of the battery pack?"

6. I occasionally arrive home with 20 miles showing, at which point the 'battery limited' warning pops up. So this would border on stressing the battery. Thus my interest on being sure the battery is not out of balance or otherwise limited.

In a case like this, balancing might actually hurt you. Battery packs can be either top-end balanced or bottom-end balanced. Think of it like lining up a bundle of sticks all with different lengths. Tesla does top-end balancing, which guarantees the bottom end will be out of balance. Running your battery down to a low SOC will put greater stress on those cells which are already lower than others at the bottom end.

 

[AmpedRealtor]

So far there is no evidence that this happens except when charging. I'd be thrilled to learn otherwise.

The evidence is on the card that was provided at purchase and which is attached to every service receipt. You have at least one of these as well. My source is Tesla itself. Good enough for me.

 

[yobigd20]

Clearly there is much debate about balancing, charge/discharge activity suggestions, etc...

One thing that seems to be universally agreed upon however, is that the two thing Lithium ION cells like are:

-Being at a SOC that's not at one extreme or the other (especially for extended periods)

-Staying cool

My question is: what's "cool"? My garage can get to be 100-110+ in the summer during the day... and even at night when I'm charging can stay 100+. What's the range for a LiON cell to be happiest?

Batteries are like people. If you are comfortable, the battery is comfortable. Best temp is around 70 degrees. Too cold or too hot and the battery, just like you, is not comfortable.

Agreed, however *unlike* the Nissan Leaf which clearly shows degradation problems in hot climates

Tesla cooling and battery management system is far superior in the roadster.

And that was first gen. The Model S is 2nd gen tech, leaps ahead of everyone else in the game (if you even consider anyone else in the ballpark, lol) and being 2nd gen tech I would expect it to be even more sophisticated and refined.

My take on that roadster study is that Tesla's perfected the battery thermal management system to keep battery temps in an ideal range in all climates such that it doesn't matter if you live in Alaska or Texas, outside temperature really has no effect on battery life in a Tesla. Great for us.

 

[TommyBoy]

I picture the real Tesla battery engineers reading these threads and laughing. I know because I work in the high-tech industry and there are many forums about one of our products and the engineers make a point of having beers in the office on Friday night and reading the thoughts of "experts". It's all over my head as a sales guy but they seem to get quite a kick out of it.

 

[yobigd20]

I picture the real Tesla battery engineers reading these threads and laughing. I know because I work in the high-tech industry and there are many forums about one of our products and the engineers make a point of having beers in the office on Friday night and reading the thoughts of "experts". It's all over my head as a sales guy but they seem to get quite a kick out of it.

I actually spent a lot of time today reading a lot of their patents and learn more on a detailed technical level so I can speak more accurately about the subject. I'm quite impressed. They're systems and methods are very sophisticated. They've got to be leap years ahead of competition. Even when (if?) the competition "catches up", Tesla's got quite the collection of patented IP regarding charging and battery management. That puts everyone else at a major disadvantage unless they can somehow "out-think" Tesla's engineers. Even while they (competition) keeps trying to catch up, Tesla's already filing patents for the next-gen technology (their metal air + lithium ion hybrid battery systems sound very cool, I'm guessing that's for Gen III).

Anywho, after reading a lot of these patents, it's quite clear to me that they have completely control over charging and the battery pack systems. I don't think that charging at 110v wall outlet vs NEMA 14-50 vs HPWC vs supercharging makes much of any difference as long as you're keeping the SOC between 10-90%. Their thermal heating/cooling system keeps the battery temps at an ideal temp pretty much at all times so I can't see how any of us can really do our battery much harm unless you range charge it to max and keep it like that for an extended period of time or vise versa - deplete the battery and keep it like that. Their advice to just "keep it plugged in" couldn't really be more true and any simpler. They have a method of calculated an estimated "rated range", but really that's it in a nutshell - it's an algorithmic estimate that tries to be as accurate as possible but in fact it is technically impossible to do so. The only way to accurately calculate a lithium-ion batteries capacity has to be to deplete it fully (bad for battery) and then to range charge it fully (also bad for battery). So basically they are left to do some mathematical tricks to "best guess" rated range based on a number of factors. It seems to be "more or less accurate". So when I read posts of people saying "hey my rated range is down 5 miles, down 8 miles, and then say *oh no I have battery range loss* , I chuckle. It's not really range loss at all. It's the weighted estimated guess. And then they come out after doing a long trip and now they see higher rated range. These estimate is going to fluctuate a good 5,10,15 miles. I wouldn't worry about any of this. Everyone should just plug their cars in at night and go to bed and sleep well knowing that Tesla knows what the hell they are doing & they are damn good at it. Make's me feel kind bad for the "other guys" trying to catch up to them lol I particularly liked how Toyota said today "there's no place in hte market for EVs" and then Tesla's stock shot straight up again! LOL! Toyota has no clue really and has to buy the tech from Tesla for the Rav4 EV bc Toyota doesn't have the in-house tech or the know how to do it themselves haha

You can read these patents yourselves. They are all published publicly.

 

[brianman]

The evidence is on the card that was provided at purchase and which is attached to every service receipt. You have at least one of these as well. My source is Tesla itself. Good enough for me.

Not every purchase included this card. Mine didn't, for example. I picked up one while I was at Fremont service (not for my car, they didn't have any room for appointments) during my Teslive trip.

Don't always believe everything Tesla prints as "fact" though. For example, the red HPWC on the back of that card was never made available to customers -- though it does exist, as there is one of them at the Fremont service center.

Somewhat random tangent, perhaps.

 

[brianman]

Warning: Keep an eye on your vehicle when trying out low charging rates

I lost track of which thread was covering the "charge at 240/6A for a few days to allow rebalancing" so if this is the wrong one, feel free to move this post.

My fuzzy recollection of my new data point is this...

A few weeks ago I had my 12V battery replaced as part of what seemed to be a general push to replace the "original" or "early" 12V batteries with the new "red" ones. My original 12V never exhibited problems. My new 12V hadn't exhibited problems -- until today.

I planned on a "hibernate at home" weekend with little driving activity, so it made for a good break from "daily driver" role to try out the slower charging rate balancing theory a bit. On Friday night, I dropped the max amperage (in car) to 5A. The car didn't seem to want to settle on a duration for a few minutes so I bumped it up to 20A and it quickly converged on a reasonable ETA. A few hours later I dropped it to 10A, and then a bit after that I dropped it to 5A and went to bed. All seemed well. I left it at 5A for all of Saturday and Sunday. No surprises, no drama.

Tonite (Monday) when I got home I plugged in with 170+mi. (maybe 180+, I forget) rated remaining. I didn't do anything special. Something reminded me to check my logs (instinct anytime I "change something in the matrix") and I noticed that charging_state wasn't "Completed" but instead read "Stopped" and that battery_level was 80. (I have the default limit of 90 set.) Well that's curious.

So I load my test app and invoke charge_start. Nothing happens. It stays at charging_state = Stopped.

I walk outside and notice my instrument cluster is lit up. Note that this is before I'm in range with the key fob so the car hasn't "been alerted to my presence" yet. Even more curious.

The instrument cluster reads "Car Needs Service" and as I get closer I see it's complaining about the 12V being low. Lovely.

Assuming it's related to the low amperage max setting, I tap the button the HPWC cable so that it goes into "plug unplugged, and replugged -- let's renegotiate" mode. Immediately I bump the amperage up to 20A. After a bit, the car is now at 83 battery_level and remains in charging_state Charging.

So it seems like -- from a charging perspective -- it's underway.


But I now have a new reason to be nervous about the 12V. With the main battery at SOC of 80% why would the 12V trickle-charging be impacted by the wall charging rate? Very odd. Makes me suspicious that something is "troubled" regarding the 12V generally.

I already had a reason to chat with the service center in the near future (second set of TPMS, for the 19s) but now I have a another topic to discuss.


Moral of the story: Keep an eye on things if you drop your charging rate to "very low" (240V/5A), just in case.

car_version = 1.33.61

 

[scaesare]

So far there is no evidence that this happens except when charging. I'd be thrilled to learn otherwise.

Indeed... your comment here seems to agree with mine that we've not seen any evidence (at least that I can recall) that the temp mgm't systems have kicked in when the car is at rest and not actively charging (plugged in or not).

Now maybe we could argue that the batteries really aren't affected much by "typical ambient temps" in the areas we live in, but the PDF that wraithnot proved a URL to (thanks!) indicates that there some noticeable effect on LiON cells with just a 10 degree spread between 20 and 30 degrees. My garage can easily exceed 45 deg. C... thus my earlier questions.

 

[Merrill]

Keeping the car plugged in at all times does not work if it does draw shore power even if not charging and you are on a TOU electric rate. I do not want to pay the electric company the higher rate, so start charging after midnight. Can someone verify that you would be using power even if you are not actually charging. There has been lots of posts on this but they all leave me confused.

 

[ZBB]

Keeping the car plugged in at all times does not work if it does draw shore power even if not charging and you are on a TOU electric rate. I do not want to pay the electric company the higher rate, so start charging after midnight. Can someone verify that you would be using power even if you are not actually charging. There has been lots of posts on this but they all leave me confused.

My experience is that the car will not draw power after charging completes. There are 2 exceptions to this:
1) If its left parked and plugged in -- at which point it will start charging every 2 days to top off. I believe it uses the scheduled charging start time to do so (this will top off for vampire loss).
2) If you remotely start cooling/heating the car, or open a door while its still plugged in. It will then draw shore power for the AC use.

When we were on vacation this summer, #1 is the behavior I noticed -- and all top-off charges happened over night (I have my scheduled charging set for 2am, so I didn't stay up to check to see if it started charging at 2am every other day...).

 

[Merrill]

Thanks ZZB, I normally charge when needed. I plug in normally when I get down to 60 to 80, otherwise it is not plugged in. I still get confused with all the different options that this forum talks about. I hear that keeping the car at a high SOC all the time is not good, so does this not happen if you keep it plugged in and it charges everyday based on your charge schedule. If you do not drive the car, then it stays at the top end of the SOC.

 

[montgom626]

Moral of the story: Keep an eye on things if you drop your charging rate to "very low" (240V/5A), just in case.

car_version = 1.33.61

No need to worry. I ran 120v at 15 amps x 4 months until I got my 240v 50 amp NEMA 14-50 installed. I run the 14-50 at 5 amp x 240v when I only need 10 kW. Never had any problems with either setup.

 

[mknox]

Keeping the car plugged in at all times does not work if it does draw shore power even if not charging and you are on a TOU electric rate. I do not want to pay the electric company the higher rate, so start charging after midnight. Can someone verify that you would be using power even if you are not actually charging. There has been lots of posts on this but they all leave me confused.

Consider it verified. I set the charge timer to 10:00 PM and left it for two weeks on vacation. I have a sub-meter on my EV outlet. The car charged every other day to the tune of exactly 5 kWh starting at 10:00 PM. It did not draw power at any other time.

Now this was summer. I'll be doing the same in mid-December so I'll be watching to see how it fares in the colder weather.