#992 just hit 30,000 miles!

[Botbldr45]

OK,
To try and unravel the mismatch previously reported I charged in Standard Mode at 16 amps.
Set charge to begin at 3AM and charging started at 16amps and concluded at 4:15 (didn't drive much yesterday) with the Tattler reporting a 97% charge of 181miles.

At 7:00 when I got into the car the VMS showed 181 miles. No clue what the display said at 4:15 cause I was asleep.................. any help?
CAC=150.16


Oh and the roadster slide switch....... been there done that..............really annoying when I do that!!! Usually only happens when the ship is flying at three sheets to the wind.


Generally when I charge, the Tattler gives me a percentage of charge relative to the charge mode. I play with the KWh average and the ideal and est mile figures because I find that that allows the car the charge closer to a 100% of the Standard Mode's potential........ or gives me a higher ideal milege figure. If I get the speedometer display 5-15 miles above the VMS display the Tattler reports a 100% charge and then I get around 186....... if the mile differential is reversed..... which is normal ..... the Tattler reports a charge of 95% to 98% before the charging cycle cuts off. The reading is then in the low 180's( or even 179 as lowest I remember). Based on previous comments and the work by Tom Saxon and EV America I guess the lower figures are consistent with the CAC/ milage work. Maybe when I reverse the Estimated and Ideal milage figures I fake the PEM out and it gives my high milage..... I don't know.

 

[djp]

Yes, we've seen reports of a correlation between how the car was driven on the last run (coming in over or under Ideal) and the level of the next Standard charge. It seems when the car is driven lightly it charges higher, and after "spirited" driving it charges lower. It's possible that high current draws throw the battery out of balance, resulting in a lower Standard charge until the BMS has a chance to balance again.

From Tom Saxton's study, the relationship between Standard range and CAC is:

Standard range = 1.2034 * CAC - 1.8581

With a 150.16 CAC that puts your predicted Standard range at 179, which is in line with your 181 number. I'm guessing that the higher number you're seeing after lightly driving the car is explained by the battery pack being better balanced than the typical pack in Tom's study.

 

[Botbldr45]

Yes, we've seen reports of a correlation between how the car was driven on the last run (coming in over or under Ideal) and the level of the next Standard charge. It seems when the car is driven lightly it charges higher, and after "spirited" driving it charges lower. It's possible that high current draws throw the battery out of balance, resulting in a lower Standard charge until the BMS has a chance to balance again.

From Tom Saxton's study, the relationship between Standard range and CAC is:

Standard range = 1.2034 * CAC - 1.8581

With a 150.16 CAC that puts your predicted Standard range at 179, which is in line with your 181 number. I'm guessing that the higher number you're seeing after lightly driving the car is explained by the battery pack being better balanced than the typical pack in Tom's study.

:biggrin:
Good ..... Now I don't feel like I'm totally crazy and ignorant of my cars workings
Thanks!
Certainly don't want to get Believers in the study mad at me....... Tom Saxton's various posts have tought me a lot about #992... I respect his work

 

[smorgasbord]

Standard range = 1.2034 * CAC - 1.8581

With a 150.16 CAC that puts your predicted Standard range at 179, which is in line with your 181 number. I'm guessing that the higher number you're seeing after lightly driving the car is explained by the battery pack being better balanced than the typical pack in Tom's study.

Hmm, at 26,815 miles my CAC is 157.10, yet my Standard charge is typically around 184. That says while I have a great battery, it's out of balance. (and so much for using Storage mode over Standard mode to keep the CAC high).

I haven't done a Range charge in ages, but I have a long drive coming up Thanksgiving Day so I will charge in Range mode. Any suggestions for what to do to balance the battery while I'm getting to the Range mode charge?

 

[hcsharp]

Hmm, at 26,815 miles my CAC is 157.10, yet my Standard charge is typically around 184. That says while I have a great battery, it's out of balance. (and so much for using Storage mode over Standard mode to keep the CAC high).

I haven't done a Range charge in ages, but I have a long drive coming up Thanksgiving Day so I will charge in Range mode. Any suggestions for what to do to balance the battery while I'm getting to the Range mode charge?

I would let it sit for an hour after the range charge. That will give it more time to balance. I know, everyone says don't let it sit at high SOC but an hour won't hurt anything and your pack will be below 20C so it really won't hurt anything. Then when you start driving, try to use at least 70% of your capacity before turning the key off. So if you stop along the way to get a bite to eat, do it at a drive-thru so you don't have to turn it off. That will give a much more accurate re-calculation of your true CAC the next time you charge. Happy Thanksgiving!

 

[wiztecy]

Hmm, at 26,815 miles my CAC is 157.10, yet my Standard charge is typically around 184. That says while I have a great battery, it's out of balance. (and so much for using Storage mode over Standard mode to keep the CAC high).

I haven't done a Range charge in ages, but I have a long drive coming up Thanksgiving Day so I will charge in Range mode. Any suggestions for what to do to balance the battery while I'm getting to the Range mode charge?

If you can check your balancing grid and its all 0's the pack is balanced and you need to do the long drive on one key turn & charge to sync things up. From having 3 packs I found out of balanced packs do affect CAC directly which the value will be lower. I also found when I did the 70% draw on one key turn then charged back to std that my ideal miles climbed and synced up with the CAC value. I did't find any great benefit of doing the Range mode charge personally and don't think it buys you all that much time in balancing, I tried it on the 1st replaced pack so I'm one of those guys who like my pack at a lower SOC and limited Range Mode charges I guess

Why would your pack be out of balance in the first place, are you doing partial charges and never letting the Roadster sit to balance after each charge? I've done partial charges, multiple draws on one charge, and I've never had my pack go out of balance. My habit is to let the pack sit for 30min-1hour at least after a std. mode charge and never had balancing issues with any of the packs.

 

[djp]

I found a quick way to balance is to let the car sit in Standard mode for a couple of days, and periodically restart the charge every few hours to top off the battery. The more cycles the better to bleed off the high bricks and top off the low bricks.

This technique would be even more effective in Range mode since the high bricks are bled off faster. Degradation while sitting in Range mode isn't a problem as long as your battery is cold.

 

[smorgasbord]

Why would your pack be out of balance in the first place...

I don't know that it is, except that using the formula based on CAC provided earlier I should be getting 187 standard range miles, not the 183/184 that I am getting. My car almost always sits for hours after being charged, btw.


As for the "drive to 30% after a range charge" thing, that isn't going to happen tomorrow. I need the extra charge to get home, so I better not be below 50% when I reach my destination. Somehow, just putting the car in park and keeping the key in and turned on while I eat doesn't seem like it would do the same thing.

Speaking of the equation, where does the "-1.8581" come from? I mean, we're talking standard miles here so why does it have anything to the right of the decimal point?

 

[djp]

Speaking of the equation, where does the "-1.8581" come from? I mean, we're talking standard miles here so why does it have anything to the right of the decimal point?

It's the y-intercept of a regression line derived from the CAC and Standard Range data from 122 cars. It should be zero - logically zero CAC should also have zero range - but Tom was able to getting a better fit with a slight offset. The variability around the regression line looks to be +/- 5 miles, so your 183/184 is still well within the predicted range compared to other cars.

http://www.pluginamerica.org/surveys/batteries/tesla-roadster/PIA-Roadster-Battery-Study.pdf

 

[Botbldr45]

What do you think of charging in range mode but limiting the charge to 200 ideal miles? If you do this daily you get extra 15 to 20 ideal miles or so cause you want to drive in Standard I would think. Maybe less then that but doesn't battery charge cooler in range at about 15 amps?. Would it help long term battery health to charge at a cooler temp regularly.

 

[wts13]

What do you think of charging in range mode but limiting the charge to 200 ideal miles? If you do this daily you get extra 15 to 20 ideal miles or so cause you want to drive in Standard I would think. Maybe less then that but doesn't battery charge cooler in range at about 15 amps?. Would it help long term battery health to charge at a cooler temp regularly.

30k - quite a milestone! (What's the current record for a Roaster?)

What was your original CAC?

Man I wish we could see the CAC on the Model S. Impossible to know how the battery is really doing when estimated range seems to change with every software update.

 

[TEG]

30k - quite a milestone! (What's the current record for a Roaster?)...

As I recall, there was someone in Germany who practically lived in his Roadster... just driving and charging all the time. I think he went past 100K miles a while back.

 

[samcarney]

As I recall, there was someone in Germany who practically lived in his Roadster... just driving and charging all the time. I think he went past 100K miles a while back.

Not a record I'm sure but I have 37,000 miles on my 2.0 Roadster #635

 

[hcsharp]

As I recall, there was someone in Germany who practically lived in his Roadster... just driving and charging all the time. I think he went past 100K miles a while back.

There are at least 2 Germans who have gone over 120k miles.

 

[Botbldr45]

What was your original CAC?


I wish I knew the original CAC but I found this car on the website in 2011 down in Miami. It was a test drive vehicle and had about 10000 miles on it. I don't know about other people's experiences but during three test drives in DC each car was charged up in range mode and driven in range mode sooooooo.......... Just quessing but with the heat in Miami and the range mode charging I'll bet poor old #992 was beat up pretty badly..

I didn't start looking at the CAC until recently when the guys refining the Tesla Tettler put that in their reports. I tried to get that value from Tesla Service on two occasions but was told that..." it was a meaningless value "...and I didn't need it! ....... Really! Yes I will get the extended battery warranty in the Spring, if it's still available, when I get closer to 36,000.

On that note: will charging in range mode with a limit of 200 miles keep battery cooler than charging on standard with no limit???

- - - Updated - - -

As I recall, there was someone in Germany who practically lived in his Roadster... just driving and charging all the time. I think he went past 100K miles a while back.

I heard that too but he lost a lot of range during that time. From the various statements over numerous threads on TMC he Did not take care of the battery and drove the car pretty hard. He was a true pioneer and thought us a lot about longevity and battery care.

 

[hcsharp]

What do you think of charging in range mode but limiting the charge to 200 ideal miles? If you do this daily you get extra 15 to 20 ideal miles or so cause you want to drive in Standard I would think. Maybe less then that but doesn't battery charge cooler in range at about 15 amps?. Would it help long term battery health to charge at a cooler temp regularly.

Bad idea IMHO. You are essentially charging up to a std charge level but doing it in range mode. This exposes the cells to higher voltage for a few minutes before it stops at 200 mi than it would if you charged in std mode. Also, it only charges at a lower temperature at the end and I don't think that's close enough to the end of a range charge for it to be significantly lower. A std charge already lowers it to 25 C.

 

[jbadger]

Not a record I'm sure but I have 37,000 miles on my 2.0 Roadster #635

Also not a record, but I have about 51,000 miles on my 2.0 Roadster #506. I bought it in January with 43-44k.

 

[strider]

What do you think of charging in range mode but limiting the charge to 200 ideal miles? If you do this daily you get extra 15 to 20 ideal miles or so cause you want to drive in Standard I would think. Maybe less then that but doesn't battery charge cooler in range at about 15 amps?. Would it help long term battery health to charge at a cooler temp regularly.

The potential problem with that plan is that I'm not sure if balancing will occur after it hits the charge cutoff. Though IIRC someone said it will balance at 80% "or higher" so maybe it'll be fine. In my opinion you should either charge at high amps in range mode or low amps in standard. I think range mode and low amps is a diminishing return.

Looking back through my Tattler logs when charging at work at 208/30A or at home at 240/24A the pack never goes over 25C when charging in Standard mode. Not sure about higher current.

 

[Botbldr45]

Thanks very much for your opinions

I was just worried about 80F, which is a little over 25C, being a point where the battery can be negatively impacted. Trying to get a cooler charge.

 

[dhrivnak]

I have been told by two rangers and this backs up some personal observation as well that the pack will balance above 85% and since the standard charge goes to 87% a standard charge will balance the pack but it will be slow and if unbalanced can take weeks. If you charge in range mode then balancing will go faster, but the higher charge is harder on the battery. But we really do not know how hard. The rangers have reiterated that occasional range charging is not a problem. I do it about once a month and my battery has been stable for over 30 months now.