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What's your 90%?

Pete90D

Fan of Red Lights
Jul 25, 2015
478
4
Bay Area, CA
Great to hear! Planning a few trips later in the year and trying to see where I can get to safely. Thanks for the info. So weird, still, to pass gas stations and think, "Meh."

I haven't had time to gather more data points, but here's a drive I did to get a ballpark estimate of what could be done if I needed to watch my Wh/mi. 208mi using ~80% charge

P90D Range Data
 

AmpedRealtor

Well-Known Member
Jun 30, 2013
6,453
4,225
Phoenix, AZ
the more I think about it, the less I think it has anything to do with balancing. It's all about voltage mapping and how the charge curve is non-linear, thus making extrapolation from lower SOC more difficult. By keeping your pack at > 90% for longer periods you are simply training the range estimate to better recognize this non-linearity and more closely match the true SOC. This is evident when you charge to 100% and the car reaches "100%", but the cell voltages are still substantially lower than 4.2 V and the car continues to charge at 40 amps. Thus, the car anticipated 100% prematurely.

I think you're right. For a couple of weeks, I charged only to 70%. After those two weeks, charging to 90% resulted in a loss of 5 miles of range. Charging to 100% showed the same 5 mile loss (253 down to 248). On a whim I decided to charge to 100% three days in a row when I had errands to run. First day it charged to 248 miles. Second day it went to 250 miles. Third day I'm back to 253. In this example, I did not need to drive the car down to single digits to recalibrate, it did so all by itself simply by charging to 100% a few times in a row regardless of how many miles I actually drove.
 

Ugliest1

S85: "Sparky"
Supporting Member
Aug 19, 2013
1,401
1,661
Victoria BC Canada
Hopefully someone will read this and provide an answer. There are so many threads about range I don't know where to start.
I have driven my P85D for about 6 weeks now. I drive 53.5 miles each way to and from work so I already have 3500 miles on it. I have the Tesla wall charger 240/40 and at 90%, it's always 225-227 rated range when I get in the car in the morning. It's been in insane mode since day one until today when I shifted to sport mode. I take the same route to work. For about the first 4 weeks I'd always be a 172-174 rated range when I'd arrive at work. It's almost all highway driving but there is a lot of road construction on the route. The last three days my rated range upon arriving at the office is in the very low 160s (161 this morning after starting at 227).

It's getting colder out but not cold enough that I set the temperature above 66 on the driver's side. Is this 10 mile swing for a 54 mile trip common? Thanks.
I'll go one step further and mention my overall "strategic" plan. Based on the odd 100% charge, if memory serves my 21-month-old S85 shows about 250-255 miles, so about 4-5% degradation. If I assume the absolute worst, like, after 15 years a 20% degradation, that still gives me 210+ miles of range (though, Roadster experience after 8 years I believe nearly all of them are still at or above 90% -- haven't checked the threads lately). Couple that with the increased supercharger routing over the same time (can anyone say "Trans-Canada"?????), it should meet my range requirements very nicely even on long trips. So I no longer obsess about the numbers (especially since, all we can trust is that calibrated-or-not range estimate -- high precision low accuracy).

I post this for those who don't really want to worry about the battery life. And, if 210+ miles isn't enough, I (will) have the option to purchase a new battery for about the same as a motor-and-transmission job in an ICE (using my special ballpark estimation analysis). So for me it's a wash. Well, except for the FAR MORE ENJOYMENT I get driving the S than I would any ICE. :)
 
I had charged to between 70% and 80% for about the first 11,000 miles and was seeing about a 6% rated range degradation. For the last couple of weeks I started charging to 90% and have seen the rated range go from 228 to 332 which now represents a 2.4% rated range degradation. It does appear that the BMS looses track of the rated range the further you keep it from 90% despite the fact that the battery will probably last longer in the long run. I'm going to back my charging back down to 85% (I only use about 50 rated miles a day) and will give it another 10,000 miles.
 
My "new" 90D (an inventory car with 800 miles range when I got it last weekend), with Range Mode enabled, is getting 257 so far.

My new 90D - 90% charge varies between 257 and 261 miles. This morning it is at 258 miles. Range mode is off. I have never turned it on.

90 Percent Rated Range.png
 

liuping

Active Member
Jul 23, 2013
2,243
927
San Diego
My new 90D - 90% charge varies between 257 and 261 miles. This morning it is at 258 miles. Range mode is off. I have never turned it on.
Have you done a 100% charge yet? I did this weekend and it was 283. Not quite the 286 it would have ideally, but I don't know how it was charged during the 800 miles it was used as a demo car.

IMG_1977.jpg


(Nice color BTW :))
 
My 60 is down to 173 on a 90%. 25k miles on it. I am starting to get concerned. My wife's 60 is holding strong at 188 at 90%, with 35k miles on it.

I am right there with you. I am at 172, I have been as low as 168 @ 90%. I lost a few miles in chunks after driving from 90% down to 15-20% or so on a couple of day trips. It consistently works its way back up to 172/173..but 100% is only 191 - 194 :( I have tried all the tricks to regain miles but this has not worked.

When new it was 191 at 90%, I have about 32,000 miles on my car.
 

mknox

Well-Known Member
Aug 7, 2012
10,104
1,900
Toronto, ON
I think you're right. For a couple of weeks, I charged only to 70%. After those two weeks, charging to 90% resulted in a loss of 5 miles of range. Charging to 100% showed the same 5 mile loss (253 down to 248). On a whim I decided to charge to 100% three days in a row when I had errands to run. First day it charged to 248 miles. Second day it went to 250 miles. Third day I'm back to 253. In this example, I did not need to drive the car down to single digits to recalibrate, it did so all by itself simply by charging to 100% a few times in a row regardless of how many miles I actually drove.

My big drop came after a summer of charging to 70% and ending the day around 30%. I noticed it when I had to charge up to 90 or 100 for a trip. Those miles seem to have been lost to me forever. No amount of deep discharge / fully charging or any of the other "tricks" mentioned here did anything more than a mile or two for me. I have heard that these batteries will show degradation more quickly at the beginning, then it will taper off quite a bit. I've been at around 220 @ 90% (245 @ 100%) for about a year now.
 
My big drop came after a summer of charging to 70% and ending the day around 30%. I noticed it when I had to charge up to 90 or 100 for a trip. Those miles seem to have been lost to me forever. No amount of deep discharge / fully charging or any of the other "tricks" mentioned here did anything more than a mile or two for me. I have heard that these batteries will show degradation more quickly at the beginning, then it will taper off quite a bit. I've been at around 220 @ 90% (245 @ 100%) for about a year now.

Yup, same boat as you. I charged to a lower % for a while since I never needed the full range during regular driving. Then when I needed 90% it wouldn't hit the same number. Nothing has changed with repeated 90% and occasional 100% charges, I remain at 219-221 for 90% charges.
 

AmpedRealtor

Well-Known Member
Jun 30, 2013
6,453
4,225
Phoenix, AZ
My big drop came after a summer of charging to 70% and ending the day around 30%. I noticed it when I had to charge up to 90 or 100 for a trip. Those miles seem to have been lost to me forever. No amount of deep discharge / fully charging or any of the other "tricks" mentioned here did anything more than a mile or two for me. I have heard that these batteries will show degradation more quickly at the beginning, then it will taper off quite a bit. I've been at around 220 @ 90% (245 @ 100%) for about a year now.

Yup, same boat as you. I charged to a lower % for a while since I never needed the full range during regular driving. Then when I needed 90% it wouldn't hit the same number. Nothing has changed with repeated 90% and occasional 100% charges, I remain at 219-221 for 90% charges.

Try charging to 100% 3-5 times in a row, I think you'll see your estimate rise.
 
This thread has scared me into setting my S85 at 90% and not worrying about it. It seems like people that set it and forget it have the least amount of degradation then those who like me try and baby the batteries. I'm going to go with a 2:00am charge at 36A (dropped the amperage on my UMC so it does not melt) to 90% and not worry about it anymore.
 
My big drop came after a summer of charging to 70% and ending the day around 30%. I noticed it when I had to charge up to 90 or 100 for a trip. Those miles seem to have been lost to me forever...

Yup, same boat as you. I charged to a lower % for a while since I never needed the full range during regular driving. Then when I needed 90% it wouldn't hit the same number. Nothing has changed with repeated 90% and occasional 100% charges, I remain at 219-221 for 90% charges.



This is unnerving to me as I'm seeing range loss while following similar charging habits, but it was my understanding that the range would be restored after repeated 90% charges. It wasn't reassuring to me that I didn't regain miles after my road trip this past weekend which included a couple 100% charges.

Who wants to be the guinea pig here? I have an idea to restore your range:

1. Access fuse box in frunk.
2. Pull yellow touchscreen fuse.
3. Pull BMS green fuse.
4. Wait 5-10 min.
5. Insert fuses in reverse order.
 

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