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90% to 100% Charge Time - 240V

bancroftc

Member
Sep 21, 2015
179
10
Austin, TX
I'm about to take my first road trip. I have only ever charged to 90% and will plan on charging to 100% prior to leaving on this trip.

My question is, does it take any longer than normal to charge from 90% to 100% on 240V? I can charge up to 40A at home, but I have it dialed down to 32A and I always get 24mi/hr charging at that level. Could I expect the same rate of charge for the top 10%?

Reason I ask is that I don't want to leave my car at 100% for an extended period of time. I'll probably charge to 90% when I get home the night before and I'll leave the next day on my trip several hours later than normal (late morning). If I max out the charge limit to 100% sometime that morning so I can leave right when I get to 100%, how much time should I give myself? One hour at 32A? More?

I understand superchargers tail off dramatically at the higher SOC's. Is that similar with 240V or would it not even be an issue since the charge rate is already relatively slow?
 

FlasherZ

Sig Model S + Sig Model X + Model 3 Resv
Jun 21, 2012
7,024
1,013
No, although at the end of the 100% charge the car will sit and do some cell rebalancing. You'll see the car show its full range but it'll still show "charging" with a very low current as it tries to top and balance the pack.

It's about the same, roughly speaking, as the rest of the charging. So for 240V / 32A, figure just about 1 hr 15 mins for 90-100%. The car will likely show "charging" for another 30 minutes, but you can unplug and drive away if you'd like.

Note that I would just set it earlier and not worry about how long it sits at 100%. I have gone 2 days before at 100%; my car still charges to 266 miles in the summer (263 in winter). My data shows my car has been at 96-100% SOC roughly 8% of its life.
 

svp6

Member
Sep 6, 2014
731
771
MN
Count on 1 hour or so - and what you cannot get in 1 hour it will not make a significant impact(you may miss the last few miles to "full"). You can set the charge from the phone, just don't forget to set charging back to 90% when you no longer need it.
 

bancroftc

Member
Sep 21, 2015
179
10
Austin, TX
No, although at the end of the 100% charge the car will sit and do some cell rebalancing. You'll see the car show its full range but it'll still show "charging" with a very low current as it tries to top and balance the pack.

It's about the same, roughly speaking, as the rest of the charging. So for 240V / 32A, figure just about 1 hr 15 mins for 90-100%. The car will likely show "charging" for another 30 minutes, but you can unplug and drive away if you'd like.

Note that I would just set it earlier and not worry about how long it sits at 100%. I have gone 2 days before at 100%; my car still charges to 266 miles in the summer (263 in winter). My data shows my car has been at 96-100% SOC roughly 8% of its life.

Excellent, thanks for the feedback! So a few extra hours at 100% won't really make any difference? So basically I might as well just do my trip charge when I plug in at night and not worry about it?
 

mknox

Well-Known Member
Aug 7, 2012
10,103
1,866
Toronto, ON
My last 90 to 100% took over two hours, with most of that time at or near 100%. It was worrisome to see 30 amps going into an apparently full battery for so long, but it eventually tapered off and finished.
 

efusco

Moderator - Model S & X forums
Mar 29, 2009
5,421
666
Nixa, Missouri, United States
So, 90-98% is probably close to normal charge rate, but that last couple of percentages can take a long time sometimes as the pack balances. You'll see the amperage tapper off dramatically. I would, if you've never charged to 100%, allow at least 2 hours as mknox points out so that the pack can fully balance and complete charging. If you have to leave before that is done, then you likely won't hurt anything, but it is good for the pack to fully charge/balance every once in a while and this seems a good opportunity for you to allow it to do so. If it sits fully charged for an hour or so, you won't really be doing any harm.
 

bancroftc

Member
Sep 21, 2015
179
10
Austin, TX
So, 90-98% is probably close to normal charge rate, but that last couple of percentages can take a long time sometimes as the pack balances. You'll see the amperage tapper off dramatically. I would, if you've never charged to 100%, allow at least 2 hours as mknox points out so that the pack can fully balance and complete charging. If you have to leave before that is done, then you likely won't hurt anything, but it is good for the pack to fully charge/balance every once in a while and this seems a good opportunity for you to allow it to do so. If it sits fully charged for an hour or so, you won't really be doing any harm.


Great feedback, thanks everyone.
 

Kalud

Active Member
May 7, 2013
1,058
285
Montreal, QC
90% to 100% (until completed) at 80A

90 to 100%.png


90 to 100% table.png
 
Last edited:

efusco

Moderator - Model S & X forums
Mar 29, 2009
5,421
666
Nixa, Missouri, United States

Great data! So to specifically address the OPs questions... you hit "100%" (235 miles rated range) SOC 36 minutes after hitting 90% SOC, but it was a total of 88 minutes before charging completed (241 miles rated)... Pretty consistent with my 'gut' timer on those things.
 

FlatSix911

Porsche 918 Hybrid
Jun 15, 2015
6,513
5,918
Silicon Valley
No, although at the end of the 100% charge the car will sit and do some cell rebalancing. You'll see the car show its full range but it'll still show "charging" with a very low current as it tries to top and balance the pack.

It's about the same, roughly speaking, as the rest of the charging. So for 240V / 32A, figure just about 1 hr 15 mins for 90-100%. The car will likely show "charging" for another 30 minutes, but you can unplug and drive away if you'd like.

Note that I would just set it earlier and not worry about how long it sits at 100%. I have gone 2 days before at 100%; my car still charges to 266 miles in the summer (263 in winter). My data shows my car has been at 96-100% SOC roughly 8% of its life.

Good information ... how often is charging to 100% recommended for rebalancing the cells?

Interesting article https://en.wikipedia.org/wiki/Battery_balancing
 
Last edited:

Cottonwood

Roadster#433, Model S#S37
Feb 27, 2009
5,088
166
Colorado
Good information ... how often is charging to 100% recommended for rebalancing the cells?

Interesting article https://en.wikipedia.org/wiki/Battery_balancing

I agree with the several posters above. I set the timed charge to start 2 hours before departure on an 80 Amp HPEC. On 40 Amps, a little longer. I usually end up leaving a little later than planned and the charging finishes 98% of the time with a 2 hour buffer.

I do a 100% charge whenever I am off on a long, multi-charge trip. Anything else extra in the battery saves some time at the first stop (perhaps only minutes). As others have said, as long as you don't leave the battery at 100%, very little, if any, degradation happens.
 

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