Roadster Owner Based Study of Battery Pack Capacity Over Time

[jfischer]

Interesting when you chart the CAC and the decline. Whats most interesting to me... unfortunately not in a GOOD WAY, is the decline of my refurbished battery!

I got the refurbished pack on 11/15 and its down from 150 to about 134 as of today....

Total History doesn't look as bad from 2010 - 2019.

Hopefully its going to stop dropping or I'm going to need another battery at this declination rate in 6 months.

 

[Story]

Thanks X.l.r.8 and tomsax -- I'll go about uploading that. And yes, AFAIK, this is the original pack.

One more question: How do I determine my serial number? The VIN decoders don't seem to produce what I'd expect.

 

[X.l.r.8]

You can go to the door shut/ windscreen or display screen, one of them (I forget which) has the display for build date and vin. It’s the last 4 numbers

 

[tomsax]

The model info and service info screens have your VIN number. The VIN sequence number is at the end, typically three or four digits depending on how early your vehicle was produced in its group.

The sample photo on the Roadster survey page shows the VIN for sequence number 217 in the US production sequence.

 

[DeedWest]

Interesting when you chart the CAC and the decline. Whats most interesting to me... unfortunately not in a GOOD WAY, is the decline of my refurbished battery!

View attachment 416314

I got the refurbished pack on 11/15 and its down from 150 to about 134 as of today....

Total History doesn't look as bad from 2010 - 2019.

View attachment 416315

Hopefully its going to stop dropping or I'm going to need another battery at this declination rate in 6 months.

This is interesting. I also had a refurb ESS put into my 2.5 Sport in November 2018. Mine had a CAC of 138 and has since dropped to 132. I've only driven about 3,800 miles on it.

 

[jfischer]

This is interesting. I also had a refurb ESS put into my 2.5 Sport in November 2018. Mine had a CAC of 138 and has since dropped to 132. I've only driven about 3,800 miles on it.

That's about when I got mine 11/2018 from Houston North SC

I started with CAC of 156 which I was amazed as that's a new pack CAC....

It dropped to 150 and hovered there for a while... now its consistently dropping as shown in previous graph...

I drove it hard this weekend as I took it to Bastrop, TX about 120 miles each way.. I range changed both ways so charge was 200 miles at least.

I'll pull the logs tonight and see where it stands my guess is it lowered it even more. 100 degree heat plus driving for 4 plus hours hard...

I'm SURE wasn't very KIND to the battery/PEM system....

 

[DeedWest]

That's about when I got mine 11/2018 from Houston North SC

I started with CAC of 156 which I was amazed as that's a new pack CAC....

It dropped to 150 and hovered there for a while... now its consistently dropping as shown in previous graph...

I drove it hard this weekend as I took it to Bastrop, TX about 120 miles each way.. I range changed both ways so charge was 200 miles at least.

I'll pull the logs tonight and see where it stands my guess is it lowered it even more. 100 degree heat plus driving for 4 plus hours hard...

I'm SURE wasn't very KIND to the battery/PEM system....

That shouldn't have had any negative impact on the battery, as Range Mode is only detrimental to the pack depending on the time it spends in a high SOC - not so much the act of Range charging in general. I've taken my Roadsters on road trips frequently - 900+ miles, and did not lose any CAC. I just made an effort to start driving as soon as the Range charge was close to being complete. I also did not let it fully complete (usually stopping it around 93% or so).

My personal suspicion is that Tesla's refurb pack quality has tanked. Rumor has it, that you & I received two of the last packs they've produced in awhile.

 

[jfischer]

Yea, I got mine to 95% and then took off. Same on trip home so see if it affected anything over the weekend.

On the pack quality question....since I got a 4 year / 50K mile warranty on mine its going to be interesting when yours or mine fails in the next 6 - 40 months... I wonder how they can recover from that if no packs are available. fingers crossed that pack doesn't fail!

 

[bolosky]

I wonder if when they install a refurbished pack that they just reset the CAC to new, and the algorithm learns the value over time. That would explain the steep drops shortly after installation, followed by a slower but still pretty big decline.

 

[im4uttx]

OK, followed the instructions, but only had a 16Gb stick (I've ordered 4Gb stick), and it appears the log was cutoff (screen reported a communication error, so I assume this is the failure for >4Gb disks.

The end of the data that was captured reported:
Approximate CAC: 155.74 Ah

Probably doesn't make sense to send this file until I get it all correctly...hopefully by the end of the week.

It reports a standard charge of 138 miles. Range charge I had up to 172 miles, but it had not finished when I had to stop it...

Mark.

 

[jfischer]

@im4uttx whats your "IDEAL" range with that CAC? Should be the default range on the VDS screen in the middle.

That would confirm that outstanding CAC you noted.

For a 150 CAC you should be looking at 175-180ish for Standard Range Ideal and 225-230ish Range Mode Ideal.

 

[im4uttx]

@im4uttx whats your "IDEAL" range with that CAC? Should be the default range on the VDS screen in the middle.

That would confirm that outstanding CAC you noted.

For a 150 CAC you should be looking at 175-180ish for Standard Range Ideal and 225-230ish Range Mode Ideal.

IDEAL range reported is 186. IDEAL in range mode is 211. So I guess that is good...and bad?

 

[jfischer]

OK, followed the instructions, but only had a 16Gb stick (I've ordered 4Gb stick), and it appears the log was cutoff (screen reported a communication error, so I assume this is the failure for >4Gb disks.

The end of the data that was captured reported:
Approximate CAC: 155.74 Ah

Probably doesn't make sense to send this file until I get it all correctly...hopefully by the end of the week.

It reports a standard charge of 138 miles. Range charge I had up to 172 miles, but it had not finished when I had to stop it...

Mark.

just FYI.

While its running you should see a progress screen showing percent in HEX (00-64). When it counts up to 64 it should be finished.

if your running vmsparser.exe when you get the file run from a command prompt

vmsparser -b *.tar

in the directory where exe and tar files are stored and it will show you all the battery data for every day its has in memory.

Mine has it since its inception... sometimes when a car goes in for service, it gets overwritten so I like to pull the logs every month or so just to have it just in case...

 

[jfischer]

IDEAL range reported is 186. IDEAL in range mode is 211. So I guess that is good...and bad?

Yes that would be about where a 155 CAC should be for "ideal" range based on survey numbers.

I figure about 45 miles more for "RANGE MODE IDEAL"

Again this is IDEAL conditions and you never get that range unless your driving downhill....lol