Question concerning timing the end of my first 100% charge

I am going to charge my P85D to 100% for the first time early tomorrow morning. I'd like to time the charge so that it ends just before I plan to leave, as the less time I leave my pack at 100% SOC the better. I'm sure a lot of you will feel the need to come and post to tell me that a few hours more or less at 100% SOC isn't going to make a lick of difference in the big picture. I'll save you the trouble and tell you I understand that. I'm still interested in timing things as optimally as I can.

So, that being the case...

I have read that people believe the pack management software may do some interesting things at the end of a 100% charge that it doesn't ordinarily get to do when charging to a lower SOC, and that these things take time. I know there is debate about whether it is pack balancing or not, etc., and I'm not trying to open that can of worms. All I am trying to find out is how much additional time I should factor in for whatever it is the pack management software might like to do this first time I am charging to 100%. I'll have about 8000 miles on the car at the time. We ordinarily charge with pretty deep cycles, and charge to 90% almost every day. A typical day has seen anywhere from 100-190 range miles being driven, depending on the weather and the day.

My plan is to charge to 90% before I go to bed, and then set a timed charge for the last 10%. I'll be charging at 56 amps, and that last 10% or approximately 30 miles would ordinarily take approximately 45 minutes or so. I want the car ready to go when I need to leave in the morning. How much more time, over and above the 45 minutes it would normally take, should I allow for whatever it is the pack management software will want to do?

Again, if you are inclined to tell me to just set it to 100% tonight, and not worry about it, please don't. I fully understand that I could do that. I'd just prefer not to.

Thanks!

Zextraterrestrial said:

truth is that it really depends on the imbalance of your pack. (and balancing possibly changed in some firmware versions a while ago)
what is your 90% charge in rated?

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Thanks.

Recently my 90% charge has been 226 in rated miles, with range mode off. When I turn range mode on that kicks up to 228 or 229.

Zextraterrestrial said:

my 90% is 228 currently but was 226 before my 100% (P85 though so #'s will be different a little)

I'd expect at least 15 min at 99 or 100%

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Thanks.

I know there is some benefit to whatever it is the pack management software is going to do, so the last thing I want to do is have to leave before it finishes, since my charging to 100% is likely to be such a rare occurrence. I'll certainly leave extra time. I'm just trying to get an idea. 15 minutes is very different than an extra couple of hours, so thanks!

Edit: I had typed the above before seeing this:

deonb said:

One data point:

My last range charge was about a month ago, and it took 4 hours after it reached 255 to tick onward to 257. I left it overnight from that point on, and it stayed at 257.

The car has always charged to 257 max on range (since day 1).

So the 'balancing act' - whatever that is, can take at least 4 hours.

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That changes things quite a bit.

Now I'm thinking I might just need to let it go, and have it possibly sit at a high SOC for hours.

Edit number two--By the way, deonb, did the charge not actually complete after you left it those four hours, and then overnight? I mean, did you never get the "Charge Complete" status message?

wraithnot said:

At least with my car, it generally takes something like 30 to 45 minutes to top off the battery if I haven't done a 100% charge in a while. It takes less time if I've done a 100% charge more recently.

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Thanks!

Since this is my first one, your experience is another argument for starting it early.

Cottonwood said:

I've see the time at the end take from 15 minutes to a couple of hours. Because you have not done a 100% charge before, I would add at least 1 to 2 hours to your expected time to complete to give you a 99% chance of completing the charge.

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Thanks. I definitely want to make sure the charge finishes, but I also don't want the car sitting at 100% SOC much longer than it needs to. Decisions, decisions.

Great Dane said:

you Could also charge to 95 percent .
have it finish at 5 am and when you get up,
on your smart phone, slide her the rest of the way
While you get ready in the morning eating breakfast
so will the car.
Btw
will be in Brooktondale NY in 3 weeks
15 miles east of Ithaca

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Thanks.

The difference between the 90 and 95% is irrelevant, though, since I can predict exactly how long that 5% should take. What I can't predict is how long the car will take to go from the time it should have reached 100% charge to actually completing the charge, and that doesn't change whether I start at 90%, 95%, or 50%.

What will be bringing you to Brooktondale?

So I started the max charge at 11:00 PM, and had expected to go to bed before it finished and wake up to a fully charged car. But I wound up staying up later than I expected to, and then since I was getting close to the time Visible Tesla was showing that the charge would be completing, I decided to watch to see what would happen.

Over the last thirty minutes or so the rated miles inched up to 251.6, and the % inched up to 100%. The amps have been decreasing during this time, and are now down to 12. For quite a while the time remaining was decreasing more slowly than what it was promising, and it stuck at 4:00 for quite a while, but it did recently move to 0 minutes remaining. The car is still charging though, currently taking 10 amps. Since it may continue on this way for quite a while, and I'm getting up fairly early, I am going to finally go to bed, and trust that it will complete charging some time in the next six hours or so.

Just wanted to report back. I'll follow up again with how it turned out, but probably not first thing in the morning.

Andyw2100 said:

Just wanted to report back. I'll follow up again with how it turned out, but probably not first thing in the morning.

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So Cottonwood wins the prize for best prediction. The charge completed fifteen minutes after I posted the message above, at 1:35 in the morning, 2:35 after I had started it. I was only adding about 90 miles, so that would ordinarily have taken about two hours. Had I allowed for an extra two hours, I would easily have been fine.

VT showed 251.6 as the rated range when the charge finished, as per the email it sent me. When I got in the car this morning, the rated range showed as 253 miles.I thought that discrepancy was odd, so I exported the VT data, and found something really odd. Check this out:

(Many lines removed. Lines around significant lines included.)

At 5:55 this morning the rated miles increased by almost 2 miles, with nothing else going on!

Anyone have an explanation for this? Note that this has nothing to do with range mode being on or off. When I got in the car (at around 7:45 AM) and turned range mode on the car then displayed rated range as 255 instead of 253.

Also, I expect the answer to this is "No", but is the car supposed to do anything funky, like shut itself down after a range charge, to save vampire loss until the drive starts? I say I expect the answer is "No", because I've never read about anything like that, and I've read a lot. I ask because when I entered the car this morning, my 17" display was off. Stepping on the brake resulted in the message pictured.



I then waited a while, as instructed, and the message never cleared. I tried a scroll wheel reset, and almost simultaneously stepped on the brake again, and one of those two things got everything straightened out.

Thoughts?

gzerninplatz said:

Maybe the system re-calibrated itself, as range charging is supposed to bring about?

By the way, thanks for doing this....I'll be going on a long, somewhat non-supercharger trip soon (Oregon desert), and really want to understand the nuances of what range charging is all about....

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Yes, I guess that could be what happened. I just would have expected it to happen immediately upon the completion of the charge, not several hours later.