New/Refurbished Battery CAC

[bonnie]

I just had my three-year annual service completed & the CAC came back at 159 -- but it is a refurbished battery. Not complaining, just reporting.

It was replaced with a refurbished battery Sept 2012, approx 10k miles ago.

 

[dsm363]

I didn't know how to find the value until recently with the OVMS but mine is at 151 after 3 years and 15,000 miles.

 

[bart513]

Bonnie do you recall if it was at 160 for the first few months or did it climbing over time?

 

[wiztecy]

Bonnie do you recall if it was at 160 for the first few months or did it climbing over time?

I don't believe bonnie has OVMS or access to her CAC and gets it from Tesla whenever she's in for a service. Its of little value anyways, each pack is unique in the way the CAC goes up and down. Unless you see your CAC diving drastically your pack is healthy. Even if you don't have a warranty on the Roadster if the pack was replaced I believe they back if up for at least a year anyways.

 

[jbadger]

I just found out that my CAC is 142 for a 4.5 year old battery with 52k miles. I get about 166 ideal miles on a standard charge.

 

[wiztecy]

I just found out that my CAC is 142 for a 4.5 year old battery with 52k miles. I get about 166 ideal miles on a standard charge.

And its stayed pretty close there, has dropped and risen since 2012 from the logs I viewed of Jesse's Roadster. So that's the point, if it hold steady and even rises thats good. It can stay steady for many many years. That's what your looking for, you don't want to see a staggering down trend within a a period of time. I think you need to look at your CAC over 2-3 years to derive a conclusion that cell / sheet failure is occurring and not the pack going through its natural cycle of equalizing and pulling up the week cells/bricks.

 

[bart513]

Thanks Wiztecy. I'll stop obsessing!

 

[bonnie]

I don't believe bonnie has OVMS or access to her CAC and gets it from Tesla whenever she's in for a service. Its of little value anyways, each pack is unique in the way the CAC goes up and down. Unless you see your CAC diving drastically your pack is healthy. Even if you don't have a warranty on the Roadster if the pack was replaced I believe they back if up for at least a year anyways.

Correct. I don't have OVMS, so I check whenever I have the car in at Tesla.

My warranty will be up in a few weeks -sad face- , but I'm not going to get the extended warranty. I purchased the battery replacement option, that's the biggest dollar hit that I could face, so the extended warranty just doesn't seem worth it overall.

 

[Doug_G]

Correct. I don't have OVMS, so I check whenever I have the car in at Tesla.

Just FYI, all you need is a memory stick and my Tesla Graphical Log Parser (or one of the other log parsers that is available).

 

[bonnie]

Also true.

 

[augkuo]

I just found out that my CAC is 142 for a 4.5 year old battery with 52k miles. I get about 166 ideal miles on a standard charge.

My CAC of #783 was around 150 for a 4 year old battery with 50k miles - #970 is currently at ~152 with 32k miles. When I first got 783, I'd get about 187, at 50k it was
at 178. We'll see how long #970 stays around a CAC of 150

 

[asgard]

Correct. I don't have OVMS, so I check whenever I have the car in at Tesla.

My warranty will be up in a few weeks -sad face- , but I'm not going to get the extended warranty. I purchased the battery replacement option, that's the biggest dollar hit that I could face, so the extended warranty just doesn't seem worth it overall.

How much are they asking for the extended warranty?
The switchpack alone would have cost me $4000 to replace. I'm glad I have a warranty.

 

[bart513]

$7K for the battery

 

[smorgasbord]

I'm not going to get the extended warranty. I purchased the battery replacement option, that's the biggest dollar hit that I could face, so the extended warranty just doesn't seem worth it overall.

Interesting. I'm of the exact opposite thinking. As you know a PEM replacement is easily twice the cost of the warranty, and I know of one v1.5 Roadster that needed a new motor for about the same money (luckily under warranty). I haven't heard anything about sheet replacements in the last year, so I'm thinking that if your battery has gone 3 years/36K miles then it'll probably be just fine moving forward. And the battery warranty doesn't include degradation, only failure. Maybe on a v1.5 I'd consider it, as the 12 volt draw on it appears to cause some issues for some people, but on a V2.5 my current thoughts (I have until May this year) is to get the extended warranty, not the battery warranty. $5K is only 33 hours of Tesla labor, not to mention parts.

 

[bonnie]

To clarify ... I didn't purchase the battery warranty. I originally purchased the battery replacement option when I purchased my Roadster, which includes degradation.

 

[tomsax]

This discussion inspired me to look at how frequency of range mode charging correlates with battery pack capacity.

Looking at the data from the survey (which agrees pretty well with the OVMS data), I have a function that predicts standard mode capacity based on miles driven. For each vehicle in the survey that has at least 20,000 miles on the odometer and has not had a battery pack swap, I calculated how much above or below the expected standard mode capacity they are, then grouped those by how often they report range mode charging.

Points above zero have higher than expected standard mode capacity, points below zero are below average.

This chart seems to be saying that vehicles that are charged in range mode frequently are more likely to report a higher capacity.

There are two caveats to this conclusion: 1) there aren't a lot of data points for frequent range mode charging, and 2) in my experience, the car underreports battery capacity when it's been a while since the last low-to-full range mode charge, so the low values may not reflect actual battery pack capacity.

 

[jaanton]

This is almost identical to my reasoning for getting the extended warranty but not the battery one. I would add that there are so many items covered, that there is a good chance of something going wrong which the service cost would approach the cost of the warranty. Let's see... Motor, PEM, TPMS, Compressor, DC-DC switch pack, heater, seat heaters, I'm sure the list will go on.

Interesting. I'm of the exact opposite thinking. As you know a PEM replacement is easily twice the cost of the warranty, and I know of one v1.5 Roadster that needed a new motor for about the same money (luckily under warranty). I haven't heard anything about sheet replacements in the last year, so I'm thinking that if your battery has gone 3 years/36K miles then it'll probably be just fine moving forward. And the battery warranty doesn't include degradation, only failure. Maybe on a v1.5 I'd consider it, as the 12 volt draw on it appears to cause some issues for some people, but on a V2.5 my current thoughts (I have until May this year) is to get the extended warranty, not the battery warranty. $5K is only 33 hours of Tesla labor, not to mention parts.

- - - Updated - - -

I'm getting really doubtful regarding the CAC number and the range calculation. Monday my CAC was 151.07 (from the OVMS) and I had a long trip which got me home with just 16 standard mode miles at around 11p.m. I set the timer to start charging at midnight. Just before it started charging I noticed that the miles had dropped to 9. After a full standard charge my CAC was down to 149.40.

I'm thinking that if CAC is calculated if the car is typically driven around the top 30% of charge, it's not measuring behavior at the low end. As the battery gets worn, it's loosing low end charge capacity not so much high end capacity. It's one thing to say there is 170 miles of charge when they are not really there if you need them.

 

[dsm363]

I haven't range charged in a long time and mostly charge on 120V outlet but CAC down to 147 after 16,000 miles and 4 years.

 

[dsm363]

I've been charging mostly on 120V outlet and CAC down to 146. Could the pack simply be out of balance?

 

[spaceballs]

I've been charging mostly on 120V outlet and CAC down to 146. Could the pack simply be out of balance?

Use memory stick grab logs and look at each brick of cells via Excel spreadsheet.