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Model s at 40,000 Miles

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No, balancing is actively managed by the BMS. Basically they either bleed off charge from higher voltage cells through a resistor or they use charge shuttling and bleed off charge from higher cells and send it to lower cells. I think with the NCA chemistry the charge slope is steep enough that they could balance anywhere along the charge slope but I think it makes the BMS unnecessarily complex to do so. In the DIY community those who top balance use a BMS that is set to bleed off charge at a specific voltage using specific circuitry for that voltage. Because of the flat middle SOC of LiFePO4 cells there is no point in trying to balance in the middle since two cells at the same voltage can have different SOC. With NCA voltage has a close correlation to SOC through the entire charge curve. My guess is that Tesla felt an occasional balancing near the end of a full charge would be enough since cell drift should not be that significant with good quality closely matched cells.
 
My guess is that Tesla felt an occasional balancing near the end of a full charge would be enough since cell drift should not be that significant with good quality closely matched cells.

I'd buy that. Tesla didn't realize that some Model S owners would be anal about battery degradation, keep their battery below 50% when possible and avoid range charges like the plague. :)

Personally, I rarely let a range charge complete. It's maybe happened only once or twice in the past year.

A completed range charge in my car is yielding 406km currently. I tried giving it 3 range charges over the weekend and they all came up at 406km. Odenator, did you see any initial jump in capacity, or did it take many days before you started to see an improvement?
 
What temperatures are you charging at? I suspect you'll get more range when things heat up again.

I have actually never seen a difference in the numbers right when a charge completes (except over the long term) based on ambient temperatures. I get 215 miles at 90% whether it's 50 F or 0 F in my garage. Will certainly keep an eye on it when spring and the "real" warmer temps come back.
 
I do a standard charge each night, and wake up with about 233-234 miles of range. [ ... ] Is balancing something I'm going to need to do if I'm constantly ridding my battery to its last slivers of juice? Anything I should look out for?

If you drive that much that you nearly empty the battery so often it is better to always do a range charge anyway. Driving a nearly empty battery is the worst thing you can do to a Li battery, way more than just charging it fully and still a lot more even than letting it sit fully charged.

Better to add something to the top so you won't have to drain it so low.
 
Slowly, my rated miles keep increasing (@41,560 miles).

Screen shot 2014-01-25 at 10.41.43 PM.png
 
Wow. How have you been charging your car (90% each day or something different)?

This is what he is doing:

To rebalance the pack, I have kept my battery charged to 100% at all times, plugging at every opportunity even if only a few miles have ticked off my battery gauge. I've been doing this since the the first week of Nov '13 after discussing my range drop with Tesla engineers.

Basically, he's doing exactly what Tesla's told everyone *NOT* to do. He's been range charging every day since November and AFAIK that is going to destroy his battery pack.
 
Except that this is what Tesla *TOLD ME* to do to correct the balancing issue. If I don't get reach 263 rated miles soon, I'll call it good and go back to standard charging.

I'd say you're probably already mostly there. Still getting 260 rated miles after 40,000 miles is amazing. I may have to do the same. I'm down to 243 or so after 15,000 miles.
 
My guess would be that the "miles ragained per day spent at 100%" curve rises most steeply when the batteries are at their greatest imbalance (in the first few days) and then gets a lot shallower while the resulting battery degradation remains the same. So, same absolute degradation per day for less and less gain. What does Tesla care whether your degradation is higher after the warranty expires, they have to take care of a complaining customer NOW.
 
I'm hearing a lot about battery degradation. However, what about the interior wear, driving dynamics. With ICE cars, you have a lot of talk about breaking in periods, maintenance issues. I'm looking for the Car and Driver 40,000 mile report.

im spending bucks and plan on keeping the car for 8-10 years. I'm trading in my 2000 S430, which still drives and looks great.
 
Wanted to update this thread.

My car has been charging to 100% every night since November 2013. Since I have started doing this, I have been able to reclaim 33 rated miles. I am now back to 264 rated miles for a 100% charge with 45,000 miles driven in less than 14 months. Based upon my battery, I have not seen any apparent degradation.

Screen shot 2014-02-24 at 10.11.28 PM.png




View attachment 40813

Everything the other posters have said is true. My wife and I love the car. We fight over who gets to drive it daily (and she never wanted to buy it in the first place). I have had minor issues such as loud panoroof noise at highway speeds, auto-popping door handles, constricting seatbelts, breezy window seals, wiper fluid jets aimed too low...and ALL were fixed by Tesla as warranty. My original 21" Conti tires lasted over 30k miles. The only real issue that I've had (other than be limited to 90kH at superchargers) was a very unbalanced battery when the car passed over 30k.

View attachment 40814

My 100% rated range actually dropped as low as 231 miles. But after keeping my car continuously fully charged, I am getting closer to my previous 263 rated miles. So I am pretty confident that I have not had any battery degradation.

View attachment 40815
 
Wanted to update this thread.

My car has been charging to 100% every night since November 2013. Since I have started doing this, I have been able to reclaim 33 rated miles. I am now back to 264 rated miles for a 100% charge with 45,000 miles driven in less than 14 months. Based upon my battery, I have not seen any apparent degradation.

View attachment 44122

wow - 3 months of charging to 100%!?!??!
 
wow - 3 months of charging to 100%!?!??!
My car is the same way. While I'm not 100% charging every day, I've done about 100 in the 8 months I've owned the car. At 23,000 miles, my 100% range charge is still 207-209 miles (209 was the range when delivered new from factory). I also severely drain my 60kW pack regularly below 10 rated miles and to Charge Now.