3.0 Battery Longevity

[ion_1]

Just to reiterate what dhrivnak mentioned, NMC is widely used in the market today. Known* users are i3, 400e, soul EV, forttwo eV, focus ev, and the vast majority of the PHEV cars (BME/Porsche/Merc/Volt/Hyundai/Ford). Although we don't know the exact type of NMC (composition, which changes and continues to change) or electrolytes used, it is a well known robust positive electrode. Just thought this would be worthwhile to mention so all those who purchased a 3.0 don't freak. Powersource has a concern as no one else has used NMC in small format cells (18650) for ev, I don't know anything about that, could be.

PowerSource makes a case for a discussion relative to the original LCO cells for lifetime. These were quite good/amazing and were a very well known and tested chemistry before introduction. The only thing that catches ones eye on the new HG2 cells is the use of small amounts of Si(O) in the negative. Others are doing this now to increase energy so it is not totally uncommon. I am not sure if LG uses it in the new ford. Regardless, we need to move forward and vast amounts of testing has been done, but there does not exist the depth of "real" calendar life as with the panasonic lco cells as these are relatively new, and it is difficult to be fully convinced. There are ways to accelerate the testing and LG/Tesla has likely examined the data carefully.

I personally like 18650 vs pouch for EV for many reasons. The Tesla 21700 cell is a newbie, certainly interesting to see the performance of these cells, but very glad they are not pouch.

Regardless of all discussions, very pleased that Tesla is supporting the roadster community.

Personally:

1) I would be happy as part of the roadsters to purchase replacement batts with new chemistries and assist Tesla with data (with a good warranty on the batt..)

2) It would be great if we could get a "lifetime" mode for the charge cycle for the higher capacity batteries that have excess miles that are not needed in normal commute.

3) Most ideal (and unrealistic): offer two battery packs, one super robust but lower capacity with much longer warranty, and one that is optimized for capacity/miles. I'm not talking two sized batteries as the lower capacity one would just be stressed more, but with respect to chemistry. It's like choosing different ICEs when buying a car (except for the warranty part).



* Journal of The Electrochemical Society, 164 (1) A5019-A5025 (2017)

 

[PowerSource]

Unfortunately that is very unlikely as the GF has moved to a different cell format that is a little larger. So they will not fit unless the battery is totally redesigned which I do not have much hope they will do.

Tesla will likely make re-manufactured (current production) Model S/X packs at the GF, so this gives hope that the 18650 form factor will still live on for some time and might translate over to the Roadster packs.

 

[BTO84]

I got my 3.0 upgrade in early October, so it's been about 4 months. In that time, I've put roughly 6K miles on the battery.

When I first got it, I did a couple of range charges both to see what it was showing and also because I had to do a long drive (and then back). The best that I saw was 344 ideal miles with a CAC of 215.04.

Since then, I hadn't needed to do a long drive, so I didn't range charge it. I noticed that the ideal miles in a standard mode charge declined somewhat, from maybe 225 to 217 or so. I looked for the first time in a long while, and the CAC had declined to 201.45, a little more than a 6% loss.

I thought that maybe the problem was that the battery couldn't balance properly with the roughly 75% SOC in ideal mode, so I range charged it, let it sit plugged in for a long time to balance, topped off, and repeated a few times.

The result of this is that the CAC improved to 202.24 (total capacity at full charge 74.36 kWh as opposed to 77.26 kWh new) and the standard range charge is back to 221. However, the best range mode charge I saw was 326, a full 18 miles less than when the battery was new (again, 4 months and 6K miles ago, so not very long ago).

I figure that one of several things may be going on, rated from best to worst in their implications:
1) The 3.0 battery has cells that have a quick initial dropoff in capacity, but then level out for a long while. I know that some of the Model S cells are like this (and I think in that case that Tesla just sells them as if they're at the plateau level). So, I should expect to stay near this capacity for a very long time, and the R80 is really more of an R74.
2) There's something wrong with my particular battery, and Tesla will just replace it for me since it's a dud.
3) The 3.0 batteries lose 30 ideal miles/10k of range (as opposed to ~3.7 in Tom Saxton's study for the 2.0 battery). So at 33K miles a 3.0 battery will have the same capacity as a new 2.0, and quickly descend after that. That is, the 3.0 batteries don't work and I spent $30K making my car be useless earlier than if I'd have kept the 2.0 battery.

I really hope that Tesla didn't screw up in cell selection and it's not #3. Or that if it is that they'll suck it up and fix all of our quickly decaying batteries.

Have any of the other 3.0 owners seen a decrease like this? How much mileage do you have on your new battery?

 

[eljf]

Hi guys,

any conclusions on the 3.0? Sounds strange to sell a product that degrades to a lower baseline spec.

Admittedly I'm so un-technical that I can't figure out how to upload a profile pic to TMC. But was DC charging or ChaDeMo really out of this planet as an upgrade? I bet some of you techcy wiz folks would have found a way.

ian m

 

[thefortunes]

There is a CHAdeMO aftermarket product for the Roadster CHAdeMo charging for Tesla Roadster

 

[eljf]

Awesome. Thanks 'thefortunes'. I was going to look this up.

Still keen to hear updated views on 3.0 upgrade.

The original Tesla post Roadster 3.0 claimed a new aero-kit + wheel system. I haven't heard anyone comment on this?

ian m

 

[hcsharp]

The original Tesla post Roadster 3.0 claimed a new aero-kit + wheel system. I haven't heard anyone comment on this?

It's kind of a sore subject. Tesla promised an aero kit, wheel bearings, tires, and brake caliper mods. They even tested them on a trip of just under 400 mi.Then they dropped the ball. They never promised a completion date so maybe they'll still release the other improvements.

 

[eljf]

I feel like a part of the Technical community now: the Henry Sharp has replied to my post

I bought your CanJR, and then ur CanSR came out, so I got that too. Expensive way to do things, but must be your good karma helping us all out (was just messaging Mark Sanders UK saying discussing this).

Another one to the list of sores suffered by Roadster owners Most will know what I mean. Still loving the car itself thou.

Still keen to hear updated views on 3.0 upgrade.

 

[bolosky]

I suspect that what's happening is none of the three options in my post that started the thread.

I while back I decided to range charge the car every day for a week, thinking that maybe it just couldn't balance properly with the new, lower standard charge. So, I did that, but it seemed to quit balancing pretty quickly, unlike when I'd gotten a new original battery years ago. However, what I saw was that the CAC steadily went up every day in the week from roughly 201 to 205.

Since then, it's gone back down on a steady decline, kind of like what it was doing when I first looked at it.

I suspect that what's wrong is that the CAC determining algorithm can't deal with the lower standard charge limit, and it (greatly) overestimates the rate of battery degradation. So, the car is confused, but the cells themselves are (probably) fine.

I guess the right thing to do it to watch it for another six months or so and see what happens.

 

[gregd]

Can you post an updated graph of the CAC trend? This may be a significant revelation.

I've been wondering about the lower standard charge SoC limit, and what that might do to balancing and so forth. In theory, keeping the battery at the lower SoC should be good for it, so the possibility of an actual deterioration was very disturbing and caused me to back off the ""buy" button. My original battery is otherwise in good shape, but I may go for the upgrade now.

 

[bolosky]

Here is the graph showing what happened to the CAC when I range charged it every day for a week, then went back to normal. When it was range charging it didn't balance all that much, so I don't think that that was the problem, which is why I suspect that it's just doing a really bad job of computing the CAC when the battery just doesn't charge full. It's telling that the slope after the range charge is pretty much the same as before it. It didn't drop faster to get back onto the same line.

I'm not sure what the end game of this is. It seems like after a year or two the CAC will be so far off the actual battery that the car will have a completely wrong idea about how much charge it has. I wonder what will happen then (maybe Tesla will just fix the software).

(BTW, this graph is a little different from the previous ones Dave and I posted, because it's a scatter graph with the odometer on the X axis rather than date. This probably doesn't make much difference for this graph, but since battery capacity seems to go with miles driven more than calendar time it seems like right thing to do.)

 

[bolosky]

Oh, and IIRC the little bump at 115,500 miles was also a range charge.

 

[ecarfan]

@bolosky thanks for posting that graph. Very interesting. I don't have any CAC numbers for 3.0 battery, but can say that for the first 6-8 months of ownership (got it June 2016) on a standard charge it would display about 236 miles of Ideal range, if I recall correctly. Then over the past 3 months I've noticed that number declining steadily and it is now at 225-226.

I range charge only occasionally. I have not tried range charging for multiple days in a row, as I've never been convinced that accomplishes anything lasting. When my 3.0 battery was new it range charged to the mid 350's like others have posted about (if I recall correctly). The last time I range charged was about a month ago and it stopped at 346. I expect some battery degradation over time, of course, and am willing to accept a 2-3% drop in the first year, but don't want more than that! After the first year I expect maybe 1% decline. I hope.

Your theory that the software is incorrectly calculating the CAC of the 3.0 battery is intriguing.

 

[bolosky]

I don't have any CAC numbers for 3.0 battery...

If you send me your log file, I'll be happy to make a graph like that for you. PM me and we'll figure out how to transfer the file if you're interested.

Your charge numbers are much higher than mine. My highest charge was in the 340s (344 or 346 IIRC), and standard charge started at 225 and then declined to maybe 218-219 after ~7.5K miles.

It would be interesting to see if you have the same or a different slope of CAC decline from me and Dave.

 

[ion_1]

View attachment 220673
Here is the graph showing what happened to the CAC when I range charged it every day for a week, then went back to normal. When it was range charging it didn't balance all that much, so I don't think that that was the problem, which is why I suspect that it's just doing a really bad job of computing the CAC when the battery just doesn't charge full. It's telling that the slope after the range charge is pretty much the same as before it. It didn't drop faster to get back onto the same line.

I'm not sure what the end game of this is. It seems like after a year or two the CAC will be so far off the actual battery that the car will have a completely wrong idea about how much charge it has. I wonder what will happen then (maybe Tesla will just fix the software).

(BTW, this graph is a little different from the previous ones Dave and I posted, because it's a scatter graph with the odometer on the X axis rather than date. This probably doesn't make much difference for this graph, but since battery capacity seems to go with miles driven more than calendar time it seems like right thing to do.)

Interesting, many thanks showing plot.The next 10% or so of fade will be telling. Similar chemistries show a decent fade upfront but then are rock solid (but as discussed, this one is slightly different beyond NMC). I assume you have done a long drive between charges bringing it down to low SOC. Then the CAC should correct itself unless there is something seriously wrong with the algorithm. Obviously at that point there is very little calculation as actual Ah and V that has passed through the system can be measured directly. Probably many eyes are on this thread (or should be). I'm certain Tesla will be feeding in and watching the 3.0 data carefully as it will factor into chemistry decisions moving forward. Maybe a sticky with semi-frequent CAC updates by 3.0 members?

 

[bolosky]

If you send me your log file, I'll be happy to make a graph like that for you. PM me and we'll figure out how to transfer the file if you're interested.

BTW, this offer is open to anyone. It might be interesting to do a big graph with lots of CAC vs. mileage curves for the original and 3.0 batteries, both.

 

[ion_1]

BTW, this offer is open to anyone. It might be interesting to do a big graph with lots of CAC vs. mileage curves for the original and 3.0 batteries, both.

That is a good idea and would be really useful to the entire community, even if just for 3.0.
CAC as a function of time would be good as a contrast. With the two then we can can extract whether charge/discharge (which somewhat scales with mileage) or calendar life is more of an issue with 3.0 chem or cell construction.

The trends are most important, so plots are really useful to extract the best info.

 

[gregd]

So, I have my 2.0 (original battery) in the shop right now for it's yearly de-leafing, and have printed out @bolosky's graph in order to have a chat with the techs when I pick it up tomorrow. Staring at it, I realized that the CAC at 115,500 and 118,500 are about the same. If the reduction in CAC were real, then why would the battery have the same CAC after 3k miles have been added to it?

The slope of the decline after the range charging is maybe slightly higher than before. Perhaps it will take a bit longer than 1.5k miles to settle down to the original trend line, but that little tail at the end suggests otherwise. So, the overall conclusion is that what we are seeing is a drift in the CAC estimate. Then again, the ambient temps are starting to increase (presumption... Where are you located?), which usually causes CAC to drift a bit higher. Hard to know which we are seeing...

 

[bolosky]

I'm in Seattle, and it's been a cool spring. I saw a piece on TV saying that we've set the record for the latest first 60 degree day (which usually happens Feb 27 and hasn't happened yet).

I only know of two reasons for the CAC to go up: better balancing the battery (which is why I started range charging it) and the CAC algorithm making adjustments.

One thing that really stood out to me is the big jump up at 111,000 miles. The car takes one measurement every day, so you can tell that I drove a long way before that happened, since that dot is far to the right of the previous one. If it's what I think, then I both range charged it and drove it nearly to empty. This should give the CAC algorithm much better data to work with. The same thing happened around 116,500 miles with the same result. All of that makes me think that Tesla just screwed up the algorithm and that the car has no realistic idea of how much battery capacity it has.

And that make me feel much better, since it's not nearly the problem that actual battery capacity declining at that rate would be.

Plus, maybe it's an excuse to drive the car on some longer trips, which is always a lot of fun.

 

[DaveD]

Plus, maybe it's an excuse to drive the car on some longer trips, which is always a lot of fun.

It's not nearly as much fun to drive long trips in a Roadster when it's cold and rainy. Spring/Summer here in the PNW can't come quick enough for me!