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#21
Mitrovic said:
My primary concern is the battery pack now.
As it is now, my 3,5 years old battery pack had a better range reading then the "brand new" battery pack I got now.....
If I think about it, I start thinking how Panasonic has stopped making those cells for a while now. So how old is my "Brand new" battery pack in reality? How was it stored?
Click to expand...

I had the same thing happen to me when I got a new battery. The problem was that the new battery was out of balance because it had been sitting unused for a very long time. The service manager told me to range charge it and let sit plugged in with a full range charge for a long time (it took a week). This resulted in the battery charging up to a much more reasonable number. It's been three years and 40K miles since then, and it's still charging up to a higher level than when I first got it.

And yes, you're not supposed to range charge it regularly, but this is an exceptional case and it's not going to hurt your battery to do it one time (even letting it sit full for a week won't hurt it). It's only if you do it all the time that it's a problem. The battery will balance with a full standard mode charge, but it will do so very slowly. I wouldn't be surprised if it took months to balance if you do that.

FYI, I've now got 60K on my car (well, more like 48K on the battery, since it was replaced with one that was newer than the car), and I've lost 7% of the overall battery capacity. So, it's doing really well overall.
 
#30
Does Tesla even have any "new" ones? I thought they stopped making those individual cells couple of years ago. Meaning whatever they have left anywhere, were/are subject to natural time degredation.

Mitrovic said:
The newest from Tesla information is that if you get a battery swap under guarantee ( even if you had to pay for the guarantee ) you get a refurbished battery. If you pay for the battery then you get a new one....
Click to expand...
 
#31
Mitrovic said:
The newest from Tesla information is that if you get a battery swap under guarantee ( even if you had to pay for the guarantee ) you get a refurbished battery. If you pay for the battery then you get a new one....
Click to expand...

Makes sense. That's what they do with the Roadsters; they replace the pack with one in similar condition. Unless one isn't available, in which case you luck out and get a brand-spanking-new one.
 
#34
The CAC isn't all that helpful if the battery is out of balance, it won't tell you the potential capacity if the battery were properly balanced, which is the number we're really interested in.

Tom Saxton's study showed that the Standard mode miles, Range mode miles and CAC are all direct multiplies of each other. If you know one then you also know the other two. The advantage of the CAC is that it takes some of the noise out of the measurement since it doesn't change with SOC. However if the battery is out of balance then the CAC will be lower, and if it's in balance the CAC will be higher, so as a measure of potential capacity it's no better than ideal miles after a Standard charge.
 
#35
djp said:
The CAC isn't all that helpful if the battery is out of balance, it won't tell you the potential capacity if the battery were properly balanced, which is the number we're really interested in.

Tom Saxton's study showed that the Standard mode miles, Range mode miles and CAC are all direct multiplies of each other. If you know one then you also know the other two. The advantage of the CAC is that it takes some of the noise out of the measurement since it doesn't change with SOC. However if the battery is out of balance then the CAC will be lower, and if it's in balance the CAC will be higher, so as a measure of potential capacity it's no better than ideal miles after a Standard charge.
Click to expand...

Tesla does know the CAC of the pack before it was pulled, that's how they know it was a healthy pack... typically they're replacing sheets/bricks in these. Its usually the case its 2 sheets that go bad and the whole pack does not need to be replaced... hence the refurbished name. Then, if executed right the low sheets/bricks bricks are replaced with sheets/bricks that match the aH (or CAC) of the rest of the pack and they get the refurbished pack that's healthy... As long as there's no issues with the BMB... and I don't know if they use the BMB that was originally in your Roadster or the BMB that was attached with the original pack, things *should* go well. Its most likely they don't want to tell you the CAC of the new pack... Thats where you have to keep record of your original CAC. Again, dump your logs or learn how so you get this data.
 
#36
djp said:
The CAC isn't all that helpful if the battery is out of balance, it won't tell you the potential capacity if the battery were properly balanced, which is the number we're really interested in.
Click to expand...
I'm only loosely following this thread, but want to double-check my understanding.

Assumption:
After "proper balancing" the CAC number will always be the same or higher than prior to balancing.
Click to expand...
Is this correct?

Scenario:
1. Shopper has a minimum CAC (A) in mind.
2. Tesla reports a non-balanced CAC (B).
3. Shopper buys vehicle (implies B >= A)
4. Shopper balances pack.
5. Shopper measures balanced CAC (C).

Can we safely assume that C >= B >= A, and thus C >= A?

Thanks.
 
#37
brianman said:
I'm only loosely following this thread, but want to double-check my understanding.

Assumption:

Is this correct?

Scenario:
1. Shopper has a minimum CAC (A) in mind.
2. Tesla reports a non-balanced CAC (B).
3. Shopper buys vehicle (implies B >= A)
4. Shopper balances pack.
5. Shopper measures balanced CAC (C).

Can we safely assume that C >= B >= A, and thus C >= A?

Thanks.
Click to expand...


First, even after the pack is balanced... the CAC can still grow. There's some things that can force a recalibration but my pack has been balanced for over a month now, but my CAC is still climbing each day. So there's no relationship that couples balancing with CAC... however before a CAC can be recalibrated correctly the pack has to be balanced first.

Second, Tesla doesn't care what the CAC is when the pack is unbalanced... it has no meaning.

"Can we safely assume that C >= B >= A, and thus C >= A?"

You may not get "B"... that's under Tesla's discretion. However this should be true: C >= A. Where "A" is a real number that can be proved/documented from the Roadster logs.
 
#38
wiztecy said:
You may not get "B"... that's under Tesla's discretion. However this should be true: C >= A. Where "A" is a real number that can be proved/documented from the Roadster logs.
Click to expand...
You've confused me somewhat by redefining A.

In the 2nd sentence, "C >= A", are you referring to my A (shopper's target minimum CAC) or your A (from your 3rd sentence)?
 
#39
brianman said:
You've confused me somewhat by redefining A.

In the 2nd sentence, "C >= A", are you referring to my A (shopper's target minimum CAC) or your A (from your 3rd sentence)?
Click to expand...

My "A" is the original pack's CAC, the one that was replaced.
My "C" is the CAC of the (Refurbished Tesla) pack that was 1st balanced and given 1-2 months to properly adjust and recalibrate the CAC.

"A" can't be a wishful value the shopper wants, it has to be a real known documented value that the Roadster logged.

Hope this clears things up.
 
#40
wiztecy said:
My "A" is the original pack's CAC, the one that was replaced.
My "C" is the CAC of the (Refurbished Tesla) pack that was 1st balanced and given 1-2 months to properly adjust and recalibrate the CAC.

"A" can't be a wishful value the shopper wants, it has to be a real known documented value that the Roadster logged.

Hope this clears things up.
Click to expand...
It clears up what you're saying but you've gone way away from my example.



I'll try again:

Shopper (no "original pack" involved) of a used Roadster has a minimum CAC (D) value in mind. Tesla reports that the potential purchase vehicle has a CAC value of E. If the shopper decides to buy (E >= D), triggers a pack rebalance, and finds a new CAC value (F). Is it guaranteed that F >= E >= D? Or might the post-rebalancing CAC (F) be less than the Tesla reported value (E) and possibly even less than the targeted value (D)?

In simpler terms, will rebalancing ever produce a value lower than Tesla reports to a prospective buyer.
 
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