CAC value can jump up and down

[wiztecy]

If you can't get the USB stick to be recognized and you placed in the correct directory name the VMS needs to be rebooted as supersnoop mentioned. There's a link I posted in the forum I contributed to that gives the details on how to do it. You can take it into Tesla and they'll do it for free, but you might have to make an appointment.

 

[Roadster]

@Carl W, here's the thread @wiztecy's was referring to:

How and where to pull plug / power to the VMS?

I tried this technique myself a few weeks ago and it worked exactly as expected. Do heed @markwj's warning though and be nice to the black and blue connectors when disconnecting them from the VMS unit.

 

[hcsharp]

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....

You've discovered one of the problems with AEdennis's theory of best charging practice. While it worked for him, it doesn't work for everybody. Tesla recommends plugging in every night because Li batteries last longer when charged for shallower but more frequent sessions. There are several reasons for this. One of them is the fact that your pack runs cooler at higher states of charge. Heat is your biggest enemy. Another reason has to do with a phenomenon called microcracking in the cathode.

To answer your question about what state of charge to begin driving more gently, it depends on a lot of factors but I generally lighten up about 50% SOC like you are doing. I think that's conservative.

 

[Carl W]

@Carl W, here's the thread @wiztecy's was referring to:

How and where to pull plug / power to the VMS?

I tried this technique myself a few weeks ago and it worked exactly as expected. Do heed @markwj's warning though and be nice to the black and blue connectors when disconnecting them from the VMS unit.

I read through the reboot procedure and because this is slightly scary to me, I want to confirm before I proceed.

Firstly, unplugging the VMS plugs can be done without first doing anything else, right? Leave the key out of the ignition and just unplug per the procedure?

Secondly, did you just lay down face up in the passenger floor area with a flashlight to do this? In other words, the VMS is visible without removing any panels? Thanks!

 

[Carl W]

You've discovered one of the problems with AEdennis's theory of best charging practice. While it worked for him, it doesn't work for everybody. Tesla recommends plugging in every night because Li batteries last longer when charged for shallower but more frequent sessions. There are several reasons for this. One of them is the fact that your pack runs cooler at higher states of charge. Heat is your biggest enemy. Another reason has to do with a phenomenon called microcracking in the cathode.

To answer your question about what state of charge to begin driving more gently, it depends on a lot of factors but I generally lighten up about 50% SOC like you are doing. I think that's conservative.

I am more concerned with battery health than with estimated miles accuracy. That being said, it's starting to bug me that my standard charge miles screen estimate keeps dropping (from high 160's 6 months ago to 154 today after 3500 miles) and so I wish there was a way to occasionally "reset" the estimation, even if that involved running the charge down very low (and gently). I ran it down to 22 miles (standard mode, so 45 in range mode) a few days ago before recharging, but it didn't help from what I can see. I welcome thoughts on all this.

 

[ML Auto]

Charging at 12 amps with the 120 volt cable will slowly bring the CAC and range up.

 

[dhrivnak]

Charging at 12 amps with the 120 volt cable will slowly bring the CAC and range up.

While true I am not sure the effect is real. Remember this is an indicator and not an actual hard value. And I have been told for the CAC to be properly reset one needs to a long range drive from 100% to below 10% something that is not easy to do.

 

[supersnoop]

I am more concerned with battery health than with estimated miles accuracy. That being said, it's starting to bug me that my standard charge miles screen estimate keeps dropping (from high 160's 6 months ago to 154 today after 3500 miles) and so I wish there was a way to occasionally "reset" the estimation, even if that involved running the charge down very low (and gently). I ran it down to 22 miles (standard mode, so 45 in range mode) a few days ago before recharging, but it didn't help from what I can see. I welcome thoughts on all this.

The estimation isn't arbitrary. There's nothing to "reset." The ideal miles are based on the car's calculation of the battery's capacity.

There are some thing you can do in an effort to provide better data to the car. Range charge it, then drive the car, in a single trip (single key-turn) down below 10%, and then charge it up again. Exercising the battery's capacity is the only way the car can learn the true capacity of the battery.

 

[ML Auto]

Nothing you do will actually add life and range to your battery. All of the numbers are just estimates. Some change by the way you drive, some by how you have driven, and some by how you charge. I've seen my CAC vary up and down by 5 points and the car still goes the same distance when driven over the same route. The CAC changes after every completed charge. My car has lost about 1 mile of range per 3K miles driven. Its best just to reset the trip odometer each charge and track it that way if you must.

 

[wiztecy]

Nothing you do will actually add life and range to your battery.

Keeping your battery balanced in a sense adds range to your battery compared to most people who never keep them balanced. Charge off of 110v and not let it sit to balance typically throws it off. Talking to Tesla Techs they are surprised when they do see a Roadster come in that is fully balanced. A fully balanced pack == more capacity == more power && more range compared to one that's not balanced.

As for adding life to your battery, you're not going to add life. You can maximize what you have. You can however follow good practices of a Lithium Ion battery to help extend its life and range. Stay away from things it doesn't like such as 100% charge while its 100+F out and such, punching the accelerator when you have 10% SOC, etc... That just stresses it out and getting stressed out isn't good for anyone or anything.

 

[Marius]

My battery is now 5 years old and has done 265.000 km. Still this week I experienced a CAC of 123 and 2 days later jumping up to 127. A battery is a chemical component and to my opinion we have to accept some movement in CAC as well in range that is directly connected with the CAC value. Like stated above keep it out of the 10% zone and out of the 90% zone.
Degradation is time past and distance driven, cannot be prevented. I will have to renew my battery within a couple of years since power coming from battery is reducing as well due to voltage lowering quicker when drawing power compared with the strenght of a new battery.

 

[wiztecy]

My battery is now 5 years old and has done 265.000 km. Still this week I experienced a CAC of 123 and 2 days later jumping up to 127. A battery is a chemical component and to my opinion we have to accept some movement in CAC as well in range that is directly connected with the CAC value..

Curious, what are your standard and range mode charge values at that CAC?

 

[Carl W]

Nothing you do will actually add life and range to your battery. All of the numbers are just estimates. Some change by the way you drive, some by how you have driven, and some by how you charge. I've seen my CAC vary up and down by 5 points and the car still goes the same distance when driven over the same route. The CAC changes after every completed charge. My car has lost about 1 mile of range per 3K miles driven. Its best just to reset the trip odometer each charge and track it that way if you must.

Losing 1 mile per 3k driven is something I'd be happy with. What are your typical charging habits? Also, do you know what the original standard charge miles shown were on a new roadster when the CAC was max?

What I gather overall from this thread is that it's best for the battery to avoid very high (100% and very low charge states), and that I should not worry about what the estimated miles are after standard charging. If that is true does it mean that I should charge to standard charge even when I've only driven 20 or 30 miles?

 

[ML Auto]

Losing 1 mile per 3k driven is something I'd be happy with. What are your typical charging habits? Also, do you know what the original standard charge miles shown were on a new roadster when the CAC was max?

What I gather overall from this thread is that it's best for the battery to avoid very high (100% and very low charge states), and that I should not worry about what the estimated miles are after standard charging. If that is true does it mean that I should charge to standard charge even when I've only driven 20 or 30 miles?

If you are only going to drive 30 miles at a time, I would only charge after every third drive. There is no need to keep it at the standard 80% charge. I would be more concerned with all the contactors that operate every time you plug in. I know their expected life is well beyond that of the battery, but since they are inside the PEM and ESS, they get very expensive and will leave you stranded if they stop working. After seeing all the electrical components with "Made in China " written on them inside both the PEM and the ESS, I try to keep unnecessary operation of those components to a minimum.

My track car has 1500 miles on it, with a CAC of 154 and charges on 15A 110V to 183 Miles.

 

[Marius]

Curious, what are your standard and range mode charge values at that CAC?

you van find my statistics in plugin america.
Standard range about 240 km, maximum range about 310 km

 

[wiztecy]

you van find my statistics in plugin america.
Standard range about 240 km, maximum range about 310 km

Doing to the online calculations that comes to:
240km = 149 miles
310km = 192 miles

I was expecting to see lower range than you reported just from previous Roadster CAC reports around that your metric.

That's great still, keep on driving it!

And I also agree 100% with MAUTO about being considerate with the charges as well as full turn key start states. This does add to contractor wear over time. Although its a beefy contactor, contactors do wear which leads resistance of the part over use and time.