I am a new 85D owner. I have had my car a little over a month and am enjoying it. I have 14-50 outlets at home and work, and they are only 14 miles apart. The car is plugged in more than 20 hours a day, during the week. I took one trip to DE so far from the NYC area. On a daily basis I only charge to about 55%, the car sits overnight at about 50%, then after my drive to work it sits at 40-45% until it charges back up to the 55-60% right before I leave. Weekends I will charge it up to 80%, and I go away to school every other weekend where it sits outside for 2 days, unplugged. The battery has never been below 20% and I have only charged it to 90% once, never above. I always get 137 miles at the 50% mark. When does the out of balance condition occur? I have 1800 miles on the car.
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What should my ideal charge percentage be?
- Thread starter Al Sherman
- Start date
Here's what I would suggest. You should balance now to establish a baseline balanced battery. Let it run down below 10% and do a full 100% charge. It takes a while so let it finish. Make note of the rated range at 100%. The next time you charge to your normal level (I think you said that number is 55%) make note of your Rated Range miles at that point. That will be your daily baseline. When you see it start slipping a couple miles from that point it's time to start thinking about another rebalancing exercise (down below 10% then full 100% charge).
FlatSix911
Porsche 918 Hybrid
I charge to 50% every day on my HPWC. The range shows 118 miles at 50% ... roughly 236 at 100% vs. 240 EPA rating. 
gzerninplatz
Member
I haven't read every post in this thread, so I apologize if this has been covered...
How can you possibly tell, when your range at a given charge drops a couple of miles (a fraction of a percent!), whether you are seeing an actual drop (the dreaded "unbalancing" that some speak of) or simply a loss of calibration accuracy? Every laptop and phone manufacturer's advice is to do the discharge/charge thing also - but just to reset the calibration, not actually to affect the capacity in any way...plus, of course, every firmware update could change the calibration algorithm...
How can you possibly tell, when your range at a given charge drops a couple of miles (a fraction of a percent!), whether you are seeing an actual drop (the dreaded "unbalancing" that some speak of) or simply a loss of calibration accuracy? Every laptop and phone manufacturer's advice is to do the discharge/charge thing also - but just to reset the calibration, not actually to affect the capacity in any way...plus, of course, every firmware update could change the calibration algorithm...
There is no way to tell that doesn't do more harm than good.
travwill
Active Member
I charge to 50% every day on my HPWC. The range shows 118 miles at 50% ... roughly 236 at 100% vs. 240 EPA rating.
Exact same range numbers here at 50%, and 100%. Your 90% probably shows 212 also I'd assume. Good to know I'm common, but expected lower since in colder climate. Expect mine to go up a bit here now that its warming up even.
FlatSix911
Porsche 918 Hybrid
Good to hear that you are maintaining 98% of the rated battery capacity.
I should also mention that I currently have 9,000 miles on my Model S.
Ken Fenske
Member
With a 90d you can get 145 miles range at 50% charge which is a lot for most my needs and this would best best for the battery. It makes me wonder what the battery life is on a Nissan Leaf with 80 miles range cause if I owned that I'd always want 100% charge just for the 80 miles.
It's supposedly better for the battery to drive in the over 50% range because the battery heats up less to give the same power (there is some speculation here based on battery information sites). It's not a speculation that charging that low over a period of time will unbalance the battery making it appear to be degrading when it's not.
It appears from the numbers posted the best results happen when charging at the full daily limit on most days. I used to charge at 80% but the battery became unbalanced. It's now back up to where is should be. (Note: To engage the balancing circuitry a charge to 93% is needed, but it shouldn't sit at that for long. Once the circuitry is engaged, then it will continue to balance the pack for quite some time (days). Based on information from TMC member WK57.)
It's mostly a myth that the Model S loses range due to imbalance. Partially charging does not bring the battery out of balance. I have been monitoring my battery voltages for some time now in all kinds of situations and never is there a difference that would cause any range loss. The differences in voltage between highest and lowest are at 0.1%. What causes a pack to get out of balance is not partial charging, it is differences (per cell or cluster) in charging and discharging and temperature between cells. Tesla has done an outstanding job in designing the battery pack so that all cells are charged, discharged and cooled/warmed very much the same. Watching the temperature and voltages of the individual modules shows that in every situation.
What does cause 'range loss' when charging partially is that it becomes impossible to measure the exact total capacity when the battery is always kept in the middle range. The battery management has to rely on a mathematical model to keep track of capacity and it's just limited in how accurate it can be. Tesla said that in an email. The closer you charge/discharge a full cycle the more accurately can the capacity be determined. Doing a full cycle can reveal previously hidden range, but it's not balancing, it's a recalibration of the battery gauge. Again, Tesla mentioned that 'recalibration' in an email.
Yes according to Jason, balancing only starts to kick in once you charge 93% or higher. But it doesn't say anything about how much the modules drift apart. As mentioned I have monitored the voltage differences over time and they hardly drift apart even if you don't charge over 90% for some time.
But yes, one way or another, it is a good thing to fully charge the battery maybe once a month or so to recalibrate the battery gage and initiate balancing.
Please share the email you are referring to. Feel free to redact any names if you need to. Me and others have received contradictory information from Tesla on this topic. Thank you.
valkeriefire
Member
Here's my battery management strategy. I wanted to run it by you all for feedback. Basically I charge my S to 90%, but only when I get below 80-100 rated miles of range (27-33%). I start changing at 3am and I get to 90% around 9am just before I'd need to drive the car. The keep my state of charge ranging from 27-90% as I don't change every night. The car is never stored at 90% and only stays at 90% for a few hours a most. This should keep the battery from developing a bad memory and its convenient since I only need to change 2x a week.
What do you all think?
What do you all think?
Sounds good. The only thing I'd add since I also have the 90D is an occasional (monthly) balancing which to me means running it down below 10-20% and then charging overnight to 100%. I know @David99 calls that recalibration but it doesn't matter what you call it just that you do it.
I have read most of the posts on this and other forums and I have watched the video by professor Dahn. The philosophies seem to fall in three camps:
1. Charge to 90% daily and forget about it. This is Tesla's simple strategy, yet seems to be contradicted by the "slider" that showed up a few years ago.
2. The "hug the middle" crowd, that seems to advocate staying around 50% so if you use 30% of your charge daily to charge to 65% so you end at 35% before the next charge. In other words, try and keep it as close to the middle as possible and avoid high and low states of charge.
3. The Dahn school, which seems to advocate minimizing states of charge at all times, but is somewhat unclear about really low states of charge. That said, at least 20% seems to be safe and maybe even a little less. All seem to say keep it above 5% and that is common sense if you don't want to risk getting stuck.
The 3rd school makes the most sense to me, and it is backed up by a PhD. that knows more than just about anyone else in battery technology. Just keep the charge at a level where you don't risk getting stuck.
1. Charge to 90% daily and forget about it. This is Tesla's simple strategy, yet seems to be contradicted by the "slider" that showed up a few years ago.
2. The "hug the middle" crowd, that seems to advocate staying around 50% so if you use 30% of your charge daily to charge to 65% so you end at 35% before the next charge. In other words, try and keep it as close to the middle as possible and avoid high and low states of charge.
3. The Dahn school, which seems to advocate minimizing states of charge at all times, but is somewhat unclear about really low states of charge. That said, at least 20% seems to be safe and maybe even a little less. All seem to say keep it above 5% and that is common sense if you don't want to risk getting stuck.
The 3rd school makes the most sense to me, and it is backed up by a PhD. that knows more than just about anyone else in battery technology. Just keep the charge at a level where you don't risk getting stuck.
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I think your treating yourself, not the battery. All you need to do is set it to 80-90% and leave it there except charge to 100% when you need to for a trip, and plug the car in every night as Tesla says. There is no such thing as the battery developing a bad memory. Have you read the manual? The part where it says to keep it plugged in when you can? In bold print?
"Remember, a connected Model S is a happy model S."
My advice-- chill out, enjoy your car, and let the battery management system manage the battery.
Good summary! Probably #3 (plus combined with slightly cooler temperature, say 40-60 F) will allow the battery to last for decades. However, only using the battery between 10-30% means a daily range of LESS than a Leaf.
Sure that's great for storage, but who buys a Tesla to store?
nikielizabeth
Member
This is great information. New 85 (CPO) owner here and had been wondering what works best. Thank you.
Ok battery gurus: I have a brand new 90D, charged only once so far to 90% after running the initial delivery charge down to about 20%. My commute uses about 80 rated miles.
I'm leaving for the weekend, and it's going to be 110-120 degrees here in AZ. I was thinking about charging to 50-60% tonight and then driving one more commute and leaving the car at around 30-35% over the weekend. I might need to drive some Monday PM when I get back so I don't want to go too low (and daytime charging is $$$ on TOU plan), but from what I am learning here if I'm leaving the car to sit in extreme heat keeping SOC as low as practicably feasible is best?
I'm leaving for the weekend, and it's going to be 110-120 degrees here in AZ. I was thinking about charging to 50-60% tonight and then driving one more commute and leaving the car at around 30-35% over the weekend. I might need to drive some Monday PM when I get back so I don't want to go too low (and daytime charging is $$$ on TOU plan), but from what I am learning here if I'm leaving the car to sit in extreme heat keeping SOC as low as practicably feasible is best?
Please just charge the car to 90% Your battery will use thermal management (cooling) while u are away and it is sitting in 120 F heart.
Best to have extra juice on hand especially if u won't be plugged in while u are way. If you are not gg to be plugged in, u def want more than 35% in the battery so the cooling can do its thing.
The battery management system controls the battery temperature. Much of the generic stuff you read about batteries doesn't apply here. Don't worry about it unless you're going to be gone for weeks. Keep your car plugged in and don't fiddle with your range setting-- keep it 80-90% unless you're going on a trip, then charge to 100% if you need to.
If your commute uses 80 miles your charge should have never gotten down to 20%. This is because you should plug in the car every night when you can. Have you read the manual? It says so twice. In bold print.
"Remember, a connected model S is a happy Model S."
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