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What should my ideal charge percentage be?

Merrill

Merrill
Jan 23, 2013
3,762
1,292
Sonoma, California
Can someone help me understand the best soc. Tesla says keep the car plugged in, yet I have read that keeping a high soc is not good for the battery life. I have a 60 and usually plug in when the mileage gets down to 80 or 90 miles left then standard charge to around 188. Is there a better way?
 

bollar

Disgruntled Member
May 1, 2013
2,667
878
Southlake, TX
The short answer is plug it in every night and if you have 4.5, set to 80-90%. Musk says 85-90% is best for most people.

The long answer is that is may be possible to squeeze additional life out of the battery by setting a lower SOC.
 

dsm363

Roadster + Sig Model S
May 17, 2009
18,278
151
Nevada
Can someone help me understand the best soc. Tesla says keep the car plugged in, yet I have read that keeping a high soc is not good for the battery life. I have a 60 and usually plug in when the mileage gets down to 80 or 90 miles left then standard charge to around 188. Is there a better way?

I agree with bollar. Probably best to just plug in each night or at least that's the easiest thing to do. If you want to dial back the SOC to 80% once you get v4.5 that'd be fine but once of the advantages of driving an EV is that you leave each morning with your full potential range (or most of it).
 

hans

P631
Sep 27, 2012
1,132
13
Menlo Park
I agree with bollar. Probably best to just plug in each night or at least that's the easiest thing to do. If you want to dial back the SOC to 80% once you get v4.5 that'd be fine but once of the advantages of driving an EV is that you leave each morning with your full potential range (or most of it).

I second that @dsm363. I plug my S60 in every night, and dial back the SOC to 80% unless I know that I need the extra range the next day. Even if I need more than 80% I try and top up in the morning right before I leave so the time spent at >80% is minimized.
 

brianman

Burrito Founder
Nov 10, 2011
17,526
2,994
Can someone help me understand the best soc. Tesla says keep the car plugged in, yet I have read that keeping a high soc is not good for the battery life. I have a 60 and usually plug in when the mileage gets down to 80 or 90 miles left then standard charge to around 188. Is there a better way?
Algorithm for those that like it simple:
Leave it at the default (90%) and plug it in every night. If you miss a night, no big deal - unlike my cell phone that kicks in to battery saver when I miss a night.

Algorithm for those that like it kind of simple but are paranoid about degradation ...
Nightly routine:
1. When you get home, make note of your remaining range
2. Plug it in
Weekly routine:
3. Evaluate the maximum remaining range for the week
4. Evaluate the minimum remaining range for the week
5. If step 3 yields > 40%, decrease your charge limit by 5%
6. If step 4 yields < 20%, increase your charge limit by 10%
7. If step 6 puts your charge limit above 90%, set it to 90%

Underlined numbers give a rough algorithm. Salt to taste, tip your waitress, all rights reversed, caveat emptor, long live the king, God save the queen, patent pending.
 

djp

Model 3 Performance
Aug 28, 2011
1,120
59
Toronto, Canada
Algorithm for those that like it kind of simple but are paranoid about degradation ...

Easier way to say that is 15% + your regular daily use. If you have a short commute and few unexpected trips then set it to 50%. If you have a longer commute or unpredictable longer trips then set it to 80-90%.
 

bob_p

Active Member
Apr 5, 2012
3,664
2,790
I'm exchanging messages with Ownership on the new variable charging feature - and continue to press that they amend the recommended charging practice in the Owners manual to explain how and why to use the new variable charge feature.

The current rules are to charge to standard almost all of the time, leaving the car plugged in whenever possible - and to only use max range charges infrequently. This is pretty simple.

If the new variable charge feature is intended to help when plugged into more expensive public chargers and cut off charging when less than a full "standard" charge is needed, then the feature is something that won't affect the overnight charging practices - and would be useful to help save $$$ when charging in the wild (i.e. not at home or on a supercharger).

BUT, if this feature was implemented to encourage owners to charge lower than 90% overnight (such as with the 7 step process listed above), then the recommended charging practice will be more complicated than the original simple rules.

So far, the feedback from Tesla Ownership is that the Model S batteries are never charged to 100% of charge (as defined by the battery manufacturer), even with a max range charge. Decreasing the overnight charging to under 90% of capacity (which could be more than the 90% we see in the car, because the reported 100% charge in the car, isn't 100% of the capacity of the batteries) helps to extend battery life - and that further decreasing the charge level will have a much smaller benefit. One of the statements in the last message was "the difference between a vehicle always charged to 90% vs. a vehicle always charged to 80% should be negligible".

Tesla should update the owners manual and the 4.5 release notes to provide more clarity on this new feature - and how it should be used.

Based on the information I've received from Tesla so far, it appears charging overnight to 90% is still the recommended practice - and the ability charge to lower levels won't have any significant benefit on the battery life.

And if this is NOT the case, then Tesla should make this clearer - and soon...
 

GaryD

Member
Apr 17, 2013
11
0
San Diego, CA
I have firmware 4.5 but my charge slider does not show a percentage like the screenshot in this thread shows???? I wish it did. Does anyone else have a slider without a percentage number?
 

bollar

Disgruntled Member
May 1, 2013
2,667
878
Southlake, TX
I have firmware 4.5 but my charge slider does not show a percentage like the screenshot in this thread shows???? I wish it did. Does anyone else have a slider without a percentage number?
Newer builds of 4.5 don't have the percentages anymore. But you still have the slider, no?
 

dtich

#P708
May 31, 2012
427
2
Los Angeles
It appears that 50% is the minimum charge you can set.

yes, 50% is the minimum charge level, it's hard-coded as a variable:

charge_limit_soc: 52,
charge_limit_soc_std: 90,
charge_limit_soc_min: 50,
charge_limit_soc_max: 100

in the examples above my current charge limit is set to 52%. this is the only variable available to users and is set by the slider. the other three are limits set by the firmware per tm. i would imagine that pulling the slider in the far left section of the charge bar simply results in setting the charge level to the minimum allowed. 50%.

(i know, 'hard-coded variable' sounds oxymoron-ish, but... you know what i mean..)
 

4SUPER9

Active Member
Jun 6, 2013
2,477
1,489
California
Just read through the whole thread. Very useful information and a good education too. Thank you all, especially those here who are exceptionally good a math.

Here is my scenario:
On workdays, I typically commute only about 10 miles/day. I also make occasional weekend trips driving about 150-200 miles or so. For the weekend trips, I will do a standard charge beforehand. Easy. I also have opportunities to charge while away.

For the weekdays, while I understand that it is recommended that I charge nightly, is it really necessary? What if I charge to 90% only once a week and just allow my range to slowly dwindle down? Again, assuming that I only drive 10 miles a day. What could I expect from this including vampire losses? How long do you think before I hit 50%? Would this put an unnecessary strain on my battery? I can't imagine any worse than someone who drives 50 miles a day and needs to charge more often.

Just call me lazy for not wanting to uncoil my cord every night (don't have a HPWC). That, and I have access to a free EV charger at work (but only once a week) where I can easily get a standard charge (my electric rate at home is absurdly high).
 
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djp

Model 3 Performance
Aug 28, 2011
1,120
59
Toronto, Canada
What if I charge to 90% only once a week and just allow my range to slowly dwindle down? Again, assuming that I only drive 10 miles a day.

Charging once a week is fine for the amount you drive the car, and you could even get away with less than 90%. I drive similar distances as you on weekdays and weekends. On Sundays I charge to 50% and by Friday the charge is down to 35% (granted there's almost no vampire drain in the Roadster). If I'm using the car on the weekend I'll charge up to Standard mode on Friday night or Saturday morning, otherwise just top back up to 50% on Sunday.

Give it a try one week at 90% and see how it goes.
 
OK all. This is a very involved thread with a lot of data that all seems to potentially be moot unless every person posting here is never going to battery swap, or if all Tesla owners agree to do what we are discussing and stick to it so the batteries are similar when we swap. I am going to go ahead an assume that neither of these scenarios are likely to be all that true.

I guess what I'm saying is that there are all these ways to extend your battery life by small percentages, and then as soon as you battery swap one time that work was all pointless.

Am I missing something here? Of course we all want all the batteries to be healthy, but there will be no way for Tesla swapping stations to certify a battery as being monitored as well aas you did your prior battery prior to getting it. So I guess either all the people on this thread are either never swapping or like the theoretical discussion.

School me if I'm wrong.

Cheers all
 

stopcrazypp

Well-Known Member
Dec 8, 2007
10,008
4,923
Am I missing something here? Of course we all want all the batteries to be healthy, but there will be no way for Tesla swapping stations to certify a battery as being monitored as well aas you did your prior battery prior to getting it. So I guess either all the people on this thread are either never swapping or like the theoretical discussion.
Tesla's battery swap station's default option is to have you pick up your original pack when you come back on the return trip (or you can have it shipped to your home).

And even if you opt to keep the station's pack, you pay the difference between the condition of your original pack and the pack you are getting.

So keeping your pack in good condition still matters.
 

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