CAC value can jump up and down

[dpeilow]

I've seen a further step down in CAC in the past few weeks and so pulled the logs. I'm wondering if I have a problem with brick 18 as until recently it was either 45 or 54 that were the consistent minimum bricks but since the step down, 18 has been the problem and is drastically pulling down the average.

Here's a snippet from the end of the log.

timestamp, brickahmin, brickahave, bricknumber

05/01/2015 19:44:48, 148.62, 151.18, 45
05/02/2015 19:44:49, 148.62, 151.18, 45
05/03/2015 19:44:48, 148.62, 151.18, 45
05/04/2015 19:44:48, 148.62, 151.18, 45
05/05/2015 19:44:48, 148.62, 151.18, 45
05/06/2015 19:44:48, 148.62, 151.18, 45
05/07/2015 19:44:48, 148.62, 151.18, 45
05/08/2015 19:44:48, 148.62, 151.18, 45
05/09/2015 19:44:48, 148.62, 151.18, 45
05/10/2015 19:44:48, 148.62, 151.18, 45
05/11/2015 19:44:48, 148.62, 151.18, 45
05/12/2015 20:03:09, 148.62, 151.18, 45
05/13/2015 23:10:59, 148.62, 151.30, 45
05/14/2015 23:11:00, 148.62, 151.30, 45
05/15/2015 23:10:59, 148.62, 151.30, 45
05/16/2015 23:11:00, 148.62, 151.30, 45
05/17/2015 23:15:14, 148.62, 151.30, 45
05/18/2015 23:15:14, 148.62, 151.30, 45
05/19/2015 23:22:03, 148.62, 151.30, 45
05/20/2015 23:22:03, 148.62, 151.30, 45
05/22/2015 00:54:49, 148.62, 151.30, 45
05/23/2015 00:54:49, 148.62, 151.30, 45
05/24/2015 00:54:49, 148.62, 151.30, 45
05/25/2015 02:04:25, 148.62, 151.30, 45
05/26/2015 02:04:24, 148.84, 151.41, 45
05/27/2015 02:04:24, 148.84, 151.41, 45
05/28/2015 02:04:24, 148.84, 151.41, 45
05/29/2015 02:04:24, 148.84, 151.41, 45
05/30/2015 02:04:24, 148.84, 151.41, 45
05/31/2015 06:25:05, 148.84, 151.41, 45
06/01/2015 06:25:04, 148.84, 151.41, 45
06/02/2015 06:25:05, 148.84, 151.41, 45
06/03/2015 09:53:02, 147.70, 150.04, 45
06/04/2015 09:53:03, 146.45, 149.36, 18
06/05/2015 10:13:48, 146.96, 149.64, 45
06/06/2015 10:13:48, 147.08, 149.70, 45
06/07/2015 10:13:47, 146.68, 149.13, 45
06/08/2015 11:21:13, 144.97, 148.05, 18
06/09/2015 11:21:13, 144.97, 148.05, 18
06/10/2015 11:21:14, 144.97, 148.05, 18
06/11/2015 11:21:13, 144.97, 148.05, 18
06/12/2015 11:21:14, 144.97, 148.05, 18
06/13/2015 11:21:14, 144.97, 148.05, 18
06/14/2015 11:21:14, 144.97, 148.05, 18
06/15/2015 11:21:14, 144.97, 148.05, 18
06/16/2015 11:21:14, 144.97, 148.05, 18
06/17/2015 11:21:14, 144.97, 148.05, 18
06/18/2015 11:21:14, 144.97, 148.05, 18
06/19/2015 11:21:15, 144.97, 148.05, 18
06/20/2015 11:21:14, 144.97, 148.05, 18
06/21/2015 11:21:15, 144.97, 148.05, 18
06/22/2015 11:21:14, 144.97, 148.05, 18
06/23/2015 11:21:15, 144.97, 148.05, 18
06/24/2015 11:21:14, 144.97, 148.05, 18
06/25/2015 11:21:14, 144.97, 148.05, 18
06/26/2015 11:21:14, 144.97, 148.05, 18
06/27/2015 11:21:13, 144.97, 148.05, 18
06/28/2015 11:21:14, 144.97, 148.05, 18
06/29/2015 11:21:14, 144.97, 148.05, 18
06/30/2015 11:21:14, 144.97, 148.05, 18
07/01/2015 12:35:26, 145.25, 148.27, 18
07/02/2015 12:35:26, 145.54, 148.56, 18

 

[dhrivnak]

Not sure it is of much comfort, but I see something very similar and have been told this is "normal"

 

[m0rph]

Exactly 1 month ago, we finally had our 230V 32A charge station up and running at the office. Before I had to charge 230V 13A using the normal outlet. It was charging all day long after my 110km commute. Now it only needs 3 hours to charge and then it can "rest" for like 5 hours before heading back home.
Since that day, my CAC just shoots up. Almost every day it's higher. Started at 144 and now at 149.8. Champagne sits cold for when I reach 150 again. Basically it's back to where it was 30000km ago. I wonder how much influence the new charger has on this.

 

[m0rph]

Champagne sits cold for when I reach 150 again.

One month and another 5000km further, I am back in the 150's!
Today 86000 km (~54000 Mls) and CAC is 150.14

When I check the Roadster Survey, I get the impression that my battery is the best of the whole pack.
Based on this calculation: 86000km / (CAC New (160) - CAC Current (150.14)) = 8722 km (~5450 Mls) per lost "CAC point".

 

[Marius]

Prepare your self for a sudden drop some point in time.
I have now 250.000 km of which 210000 done with the current pack. My CAC is 134, so 26 CAC points down makes 8000 km per CAC point. But I am coming from 129 and still climbing.
The battery is a chemical process and rates can vary.
Nevertheless the pack is performing well and with the JdeMo solution for DC charging you can postpone replacement more years.
But look into another thread. I have noticed that also the pack gets "tired". The maximum power can not be delivered anymore when your CAC goes under 140.

 

[m0rph]

Good to hear yours is still piling up the mileage with already 210000km on it. If you're still able to have an average of ~8000 km per CAC point, I don't expect a sudden drop from my pack. The lowest CAC I have seen is 144, but that was 20000 km ago. Then my average was only ~4000km/1 CAC.
I've seen the other thread and maximum power is the last of my worries, as I'm on the highway at legal speed for 90% of the time.

 

[wiztecy]

My ESS came back from a drop and recovered. I may have dropped down to 147/148CAC where my ideal std miles were around 174 coming from 152/153cac @ 181 ideal std miles. The drop occurred over a few months, then it climbed back up. I'm now at 152.50 CAC. Interesting enough, I had my ideal miles get recalculated. Before when I was at 152 and higher, my ideal miles charged up to 183/184 tops. That was even when my CAC peaked at 160, when it was at 152 last time, the ideal miles were at 181. Currently at this 152 benchmark, I'm seeing 184/185 ideal miles consistently. Note that when I take my cac/ideal mile readings its after a std. mode charge, pack is fully balanced. Even when balanced I wait a minimum of 1hr. so the battery can settle in.

Drops can occur at any given time, but we know they're induced also by a pack's that's stressed where the weakest brick takes the rest down. As our Roadster's age we need be mindful in order to wring out as much life out of these packs (orig. chemistry) as possible. As for how and why the CAC climbs back up, that's still a mystery as we all have our theories. But best practice is to follow good practice and care for your pack.

I have about 40k miles on the current refurb'd ESS, Roadster has 56k total and I typically charge with 220v@32amps.

 

[Carl W]

My ESS came back from a drop and recovered. I may have dropped down to 147/148CAC where my ideal std miles were around 174 coming from 152/153cac @ 181 ideal std miles. The drop occurred over a few months, then it climbed back up. I'm now at 152.50 CAC. Interesting enough, I had my ideal miles get recalculated. Before when I was at 152 and higher, my ideal miles charged up to 183/184 tops. That was even when my CAC peaked at 160, when it was at 152 last time, the ideal miles were at 181. Currently at this 152 benchmark, I'm seeing 184/185 ideal miles consistently. Note that when I take my cac/ideal mile readings its after a std. mode charge, pack is fully balanced. Even when balanced I wait a minimum of 1hr. so the battery can settle in.

Drops can occur at any given time, but we know they're induced also by a pack's that's stressed where the weakest brick takes the rest down. As our Roadster's age we need be mindful in order to wring out as much life out of these packs (orig. chemistry) as possible. As for how and why the CAC climbs back up, that's still a mystery as we all have our theories. But best practice is to follow good practice and care for your pack.

I have about 40k miles on the current refurb'd ESS, Roadster has 56k total and I typically charge with 220v@32amps.

Can somebody help me to get my CAC data? When I plug in a USB drive into my car, it doesn't work. Can you give specific instructions such as whether the car should be turned on or not? I know the size of the USB must be small, and the one I'm using apparently came with the car originally. Thanks!

Also, after I load the drive, then do I just put in my computer and it will read the file? Is it okay to use a MAC?

 

[AEdennis]

@Carl W sometimes I have to replace the USB drive with a newly formatted 2GB drive to get the logs to load...

Two years ago, I thought I was having some problems with my wife's CAC and have some blog posts (and TMC posts that I need to find and link to this post...)

 

[sethr]

Can somebody help me to get my CAC data? When I plug in a USB drive into my car, it doesn't work. Can you give specific instructions such as whether the car should be turned on or not?

The key should be inserted, but not turned, and the Roadster should be unplugged.

 

[AEdennis]

@Carl W sometimes I have to replace the USB drive with a newly formatted 2GB drive to get the logs to load...

Two years ago, I thought I was having some problems with my wife's CAC and have some blog posts (and TMC posts that I need to find and link to this post...)

Here are some links to the CAC challenges that we had with #40 and what steps I took back then...

Rebalancing the Roadster Pack.

Here's the thread I started back then here (on TMC).

Update on CAC testing, etc.

Roadster road test and CAC recovery...

Here's a good English response to a conversation I had on CAC with Talkredius that he posted on TFF (the German Language Tesla Forum...). He has hundreds of thousands of miles on his Roadster and a good guy.

Bottom line for us, we try to drive the car down to below 40 miles of range, then charge the car up on Standard Model. She used to plug in every day after a 60 mile commute and the CAC value dropped by a lot when we used to do that fothe first year of our CPO ownership.

 

[gregd]

The key should be inserted, but not turned, and the Roadster should be unplugged.

No key needed, actually. The car can even be plugged in, but it cannot be "on" or actively charging. I use a 4gb stick, with a directory named VehicleLogs (believe to be CaseSensitive) at the top level. The stick's access LED should begin blinking a few seconds after being inserted, and the VDS will beep an alert to you not to remove the stick until it's done blinking (several minutes).

 

[Carl W]

Here are some links to the CAC challenges that we had with #40 and what steps I took back then...

Rebalancing the Roadster Pack.

Here's the thread I started back then here (on TMC).

Update on CAC testing, etc.

Roadster road test and CAC recovery...

Here's a good English response to a conversation I had on CAC with Talkredius that he posted on TFF (the German Language Tesla Forum...). He has hundreds of thousands of miles on his Roadster and a good guy.

Bottom line for us, we try to drive the car down to below 40 miles of range, then charge the car up on Standard Model. She used to plug in every day after a 60 mile commute and the CAC value dropped by a lot when we used to do that fothe first year of our CPO ownership.

Thanks for the good info, Dennis. I've been typically plugging in whenever it's down to around 100 to 120 ideal miles, although I've driven it down to 20 miles remaining on a couple of round trip drives to san diego. Plugging in at night is so easy and I thought it was best for the pack to keep it charged to standard mode. I have wondered what's best for the car and I'll try driving it down to lower miles and see how it does. 6 months ago when I bought it, a standard charge gave about 166 to 170 miles but now it's more like 157 to 159. I do find that at 63 to 65mph (with AC off), I can usually get the exact miles that are estimated. Noticeably less at 70mph or higher.

 

[AEdennis]

Thanks for the good info, Dennis. I've been typically plugging in whenever it's down to around 100 to 120 ideal miles, although I've driven it down to 20 miles remaining on a couple of round trip drives to san diego. Plugging in at night is so easy and I thought it was best for the pack to keep it charged to standard mode. I have wondered what's best for the car and I'll try driving it down to lower miles and see how it does. 6 months ago when I bought it, a standard charge gave about 166 to 170 miles but now it's more like 157 to 159. I do find that at 63 to 65mph (with AC off), I can usually get the exact miles that are estimated. Noticeably less at 70mph or higher.

Glad I can help Carl. Ideal miles definitely is not rated for anyone with any weight in their accelerator foot.

 

[Carl W]

Glad I can help Carl. Ideal miles definitely is not rated for anyone with any weight in their accelerator foot.

At what state of discharge should you no longer "floor it"? I know that max acceleration causes a voltage drop and isn't good for the batteries when they are below some point of charge, but not sure when that is. I've been assuming don't floor it when it's below about 50% charge, but I assume that's conservative. Thoughts? This is the only problem that I have with regularly letting the car go down to 40 miles or so. It's not really me, but my wife has a lead foot....

 

[Carl W]

I've now tried three different memory sticks:

1GB "tesla" stick (already has the VehicleLogs folder). FYI, the VehicleLogs folder is empty so perhaps no previous owner ever downloaded the info before.
1GB stick that I added the folder VehicleLogs
2GB stick that I added the folder VehicleLogs

All three sticks light up when inserted (2 of the 3 blink) and then after about 20 seconds my display says "memory stick transfer failure. reinsert stick and try again" or something like that. Reinserting gives the same message. Any advice?

 

[gregd]

All three sticks light up when inserted (2 of the 3 blink) and then after about 20 seconds my display says "memory stick transfer failure. reinsert stick and try again" or something like that. Reinserting gives the same message. Any advice?

I think I got that once when the car was on (or I turned it on) while trying to grab the logs. Safest is to have the key out and not plugged in, or if the car is plugged in, do it when the car is not scheduled to start charging within the next 15 or so minutes. Failing that, perhaps the system needs to be rebooted, as some process appears to be stuck.

 

[supersnoop]

I think I got that once when the car was on (or I turned it on) while trying to grab the logs. Safest is to have the key out and not plugged in, or if the car is plugged in, do it when the car is not scheduled to start charging within the next 15 or so minutes. Failing that, perhaps the system needs to be rebooted, as some process appears to be stuck.

Sounds like you need to reboot the VMS. I believe that's the blue plug in the passenger footwell. Search here for better instructions.

 

[Nvbob]

"memory stick transfer failure. reinsert stick and try again" or something like that.

I also had this occur yesterday when doing my monthly log backup. Today, the stick did not even light up. After checking the flash drive to make sure it's not full or corrupted and has the correct VehicleLogs folder, I reinserted it but the car will not recognize the stick. I have been using this stick since we got our car six years ago. I then tried another similarly configured stick with the same result. Since our car still has it's ESA and we have an upcoming service, I will mention it to the SC to see what they say.

 

[dhrivnak]

At what state of discharge should you no longer "floor it"? I know that max acceleration causes a voltage drop and isn't good for the batteries when they are below some point of charge, but not sure when that is. I've been assuming don't floor it when it's below about 50% charge, but I assume that's conservative. Thoughts? This is the only problem that I have with regularly letting the car go down to 40 miles or so. It's not really me, but my wife has a lead foot....

The car should take care of this automatically. When my range drops below about 40 miles (including the range mode buffer) the car drops into range mode and power is cut in half. Still safe but 0-60 drops to about 6 seconds. This is the same behavior as driving in range mode.