Devil's Advocate - Charge it to 100%

[seantay00]

Common wisdom by Tesla owners is not to charge all the way "because its bad for battery longevity". While I don't doubt it may be better for the battery to partial charge, I'm curious if it really matters.

We purchased high performing cars, why not charge them the all the way and enjoy the vehicle to its maximum performance. I was looking at the performance curves below. If you charge your M3 to say 80 to 90% like most, then you'll spend alot of your time in the 50% to 70% SOC range, which essentially lowers performance by around 25 to 35HP. Even more in cold weather regions.

If you actually charged to 100%, you'd spend most of your driving in the 70% to 90% range... essentially maximizing the vehicles performance at all times.

So the question is what is the opportunity cost of really charging to 100% all the time over say 10 years.

• Battery degrades by an extra 5%? (Does one care if you're only using 80% of the battery anyways...)
• Vehicle resale drops by an extra $500? (Unlikely trade-in will offer any difference. A small price to pay for 100% performance?)
• Efficiency hit charging from 80% to 100% (Maybe a consideration point if not nominal)

Other considerations:

• Full charge savings (If I charge at work or mall for free that gives me 62 free miles every charge, savings ~$2 of home charging each time x 100 charges year x 10 years = $2K charge savings)
• Future battery advances (10 years a new battery replacement might cost $5K and have tech that runs 600 miles... in which regardless one might swap)
• Future battery repairs (It's reasonable to think someone will go into the business of battery refurb. So if charging to 100% caused a couple hundred battery failures, they might be able to be replaced at a nominal price of a couple hundred bucks anyways = cheap price for fun)
• Depreciation of unused asset (assume battery is around $20K of what we paid, charging to 80% means not using around $4K of what you paid for... in 10 years that $4K will depreciate by around 75% even if not used... wasting $3K of today's spent cash. Penny wise pound foolish?)

Curious to your thoughts. What's the actual quantified justification to not getting everything out of our M3 today, opposed to be stingy of savings a couple miles out of the battery in the long run.


https://i0.wp.com/www.mountainpassp...8/08/Tesla-Model-3-SOC-Dyno-Results.jpg?ssl=1

 

[DrSmile]

Perhaps I'm reading the graph wrong? It looks to me like the torque and acceleration is pretty much the same no matter what the charge until you exceed 60mph.

 

[ronm2948]

Perhaps I'm reading the graph wrong? It looks to me like the torque and acceleration is pretty much the same no matter what the charge until you exceed 60mph.

The graph is metric, so the speed is 60km/h or about 36mph.

 

[eprosenx]

When charging to 100% you won’t have revenue until SOC falls low enough.

I personally really like regen. The feel of the car with it is great. Having to brake is lame.

Also, you will replace brakes a lot more often without regen.

 

[ewoodrick]

Most people don't use 100% of their car all the time. You can't even do 0 to 60 at every stop, and you have the chance of being pulled over.
Are you expecting to only discharge to 90% to keep the performance high?

If you are going to drive that hard, then go for it.

But that's not for me.

 

[cypho]

Does charging to 100% every day void the warranty? If not, then even if charging to 100% does eventually destroy the battery, the replacement cost would be on Tesla, not you.

And you could potentially end up better off. If you abuse the battery and end up with a warranty replacement in year 7, your car could end up in much better condition at year 10 than it would have been if you had babyed it for 10 years.

And if it takes longer than 8 years for the full charges to cause a problem, then it is pretty hard to say that it was the full charges that caused the problem. A dead battery at year 10 is probably more about the battery being old than it is about how you charged it.

 

[zhu-]

Perhaps I'm reading the graph wrong? It looks to me like the torque and acceleration is pretty much the same no matter what the charge until you exceed 60mph.

That makes it seem like the initial power is software limited then. Maybe a safety decision by Tesla to limit power until it's consistent in all scenarios?

Does charging to 100% every day void the warranty? If not, then even if charging to 100% does eventually destroy the battery, the replacement cost would be on Tesla, not you.

And you could potentially end up better off. If you abuse the battery and end up with a warranty replacement in year 7, your car could end up in much better condition at year 10 than it would have been if you had babyed it for 10 years.

And if it takes longer than 8 years for the full charges to cause a problem, then it is pretty hard to say that it was the full charges that caused the problem. A dead battery at year 10 is probably more about the battery being old than it is about how you charged it.

Charging to 100% daily doesn't void your warranty, but I don't believe the 8-year warranty applies to wear and tear. You would get a new battery if there was a defect, but not because it only holds a 70% charge now because it was heavily used. Even after 10 years of charging to 100% you'd probably still have more range than a new Leaf.

 

[seantay00]

Does charging to 100% every day void the warranty? If not, then even if charging to 100% does eventually destroy the battery, the replacement cost would be on Tesla, not you.

And you could potentially end up better off. If you abuse the battery and end up with a warranty replacement in year 7, your car could end up in much better condition at year 10 than it would have been if you had babyed it for 10 years.

And if it takes longer than 8 years for the full charges to cause a problem, then it is pretty hard to say that it was the full charges that caused the problem. A dead battery at year 10 is probably more about the battery being old than it is about how you charged it.

This is an outstanding point I didn't even think about!

 

[seantay00]

Most people don't use 100% of their car all the time. You can't even do 0 to 60 at every stop, and you have the chance of being pulled over.
Are you expecting to only discharge to 90% to keep the performance high?

If you are going to drive that hard, then go for it.

But that's not for me.

Nobody uses "100%" of their cars capabilities all the time, but most drive over 35MPH on a daily basis. In fact most passing is done above 35MPH, and performance is notably lower on passing as SOC is lower. For many this is fine, but we paid $58K for our cars, not utilizing (or enjoying) their performance to maybe save a couple miles of battery charge in 9 years seems strange.

Right now I've been following the current guidelines to 90%, but I'm strongly considering just letting it go up to 100% from now on when I charge. I was merging onto the highway the other day after a full charge and noticed acceleration I had never felt out of the car from about 35 to 55 MPH range. A shame for most to never experience.

 

[DB-Cooper]

I don't lose too much sleep about where my SOC is at any given time. A few comments though:

1. I don't think 100% provides necessarily better performance than 90%, so charging full for better performance isn't a sound reason to do it.

2. I mostly charge at the Airport, the grocery store we frequent or my wife's work. As such, I home charge mostly for top offs or to maintain charge if we're out of town for a while. I have mine set to 90% based on Tesla guidance. I don't plug it in everyday at home because honestly plugging in and unplugging daily adds quite a bit of hassle to driving a car. I love never needing gas, but I don't drive enough to justify it, so I'm rarely really sitting at 90%. My normal battery SOC is probably 70%, I do make an effort to keep it between 50-90% per Tesla guidance, typically that is easily handled as I travel multiple times per month and can charge at my airport parking facility. Worse case, I let my wife take it to work for a charge there.

3. When at the airport or my wife's work, I do often bump the charge to ~95% right before I arrive or close to when my wife leaves work. By time the car is home, it's closer to 90% anyways. I've read the issue with higher SOC is more that it's constantly there versus short periods of time.

Anyways, I don't lose sleep over this stuff like many people do here. In the ICE world, it's like losing sleep over the amount of detergent added to premium gasoline or how much ethanol is in the fuel, how old are the tanks, etc. I do know there's sound logic that keeping batteries in their sweet spot is worthwhile, but outside of a long trip, I don't see any reason to go to 100% all the time, I'll heed Tesla's guidance except for when road tripping. I don't think the performance of 100% vs 90% makes sense for me. Given I have 32A/240V charging at home and various destination charging options that are in our day-to-day lives, outside of long road trips, I never have an excuse to be below 50%.

 

[PoitNarf]

I do as Tesla recommends and only charge to 100% for the start of long road trips. My 3 is plenty fast for me. I’m not taking it to the track or anything like that. If I’m somehow missing on a little more power for the limited amount of time my car would be above a 90% SOC so be it. I plan on keeping my 3 for at least 7 years and would rather try to keep the maximum range as high as possible by following Tesla’s suggested charging habits.

 

[SomeJoe7777]

Tesla tracks every parameter of what you do to the car. And they sometimes will act on it or restrict it to prevent battery degredation and/or a possible warranty repair or replacement. Precedent for that has already been seen in two different instances:

1. Model S P90D vehicles tracked the total number of full-power launches, "rolling mashes", and several other parameters and stored them on-board and reported them to Tesla. Tesla subsequently limited the maximum horsepower of those vehicles that exceeded a certain quantity of those operations, ostensibly to prevent premature battery failures. Enough outrage caused Tesla to remove those limitations, but only after a concerted effort of many people.

2. Some Model S vehicles had their maximum supercharging rate limited by Tesla when the number of DC fast charges (from supercharging or Chademo) exceeded a certain number, again ostensibly to prevent premature battery failures. To my knowledge, those vehicles are still limited.

If you want to charge to 100% all the time, go ahead, but do not be surprised if Tesla subsequently limits your car in some way. It's contrary to their recommendation, so they might decide that for the good of your battery, you might need more limits applied. And you may not have any recourse, either.

 

[datoda]

Charging to 100% daily doesn't void your warranty, but I don't believe the 8-year warranty applies to wear and tear. You would get a new battery if there was a defect, but not because it only holds a 70% charge now because it was heavily used. Even after 10 years of charging to 100% you'd probably still have more range than a new Leaf.

Your post made me hunt down the warranty info (https://www.tesla.com/sites/default/files/downloads/tesla-new-vehicle-limited-warranty-en-us.pdf) and give it a once-over on the 'battery and drive unit' section. In essence, there's no exclusion on wear and tear. If Tesla determines your battery's capacity is below 70% before 8 years are up or 120k miles are registered, then you are covered.

However, you do need to follow the recommended battery maintenance and charging procedures provided in your owner's manual, or the warranty is voided. The owner's manual doesn't say you shouldn't charge to 100%. It does, however, warn against fully discharging the battery. It also recommends 'leave your vehicle plugged in' when you are not using it. Given that Tesla tracks everything done to your M3, you might want to do that as much as you can so that you are on a solid ground in case you need to make a battery warranty claim.

 

[FlyinLow]

Many people use chill mode...I do to save tire wear and maximize range. I see no difference in performance until below 35%.

 

[Perry]

Many people use chill mode...I do to save tire wear and maximize range. I see no difference in performance until below 35%.

I see performance degradation below 65% SOC. The acceleration restriction (dots on the right side) appears faster.

 

[ItsNotAboutTheMoney]

Depends.

 

[Matt L]

I don’t even like going to 90% because you don’t get full regen. The car drives completely different without regen.

 

[SageBrush]

Nobody uses "100%" of their cars capabilities all the time, but most drive over 35MPH on a daily basis. In fact most passing is done above 35MPH, and performance is notably lower on passing as SOC is lower. For many this is fine, but we paid $58K for our cars, not utilizing (or enjoying) their performance to maybe save a couple miles of battery charge in 9 years seems strange.

Right now I've been following the current guidelines to 90%, but I'm strongly considering just letting it go up to 100% from now on when I charge.

You can have most of your cake and the icing too by charging up to 95% instead of 100%. High SoC related degradation can be mitigated further by finishing your charge close to the time when you will use the car. A warmed up battery in the winter does a lot more for 'performance' than 100% SoC charging.

 

[longshot49]

I don’t even like going to 90% because you don’t get full regen. The car drives completely different without regen.

I'll echo this and say my daily is at 80% because I love having full regen available.

90% : you get about 20 miles "slight" limited regen.

I would charge to 85% if there were an easy way to set it at that SOC.

 

[NickFie]

I don’t think 100% is good for daily use. Tesla recommends 90% max daily charge for a reason - battery chemistry and longevity.

When on road trips, I generally try to start each day with 100% charge. Our Model S gives a warning message about avoiding repeated 100% changes by about the 3rd 100% in a trip.

On most recent trip, timed charge perfectly. Battery hit 100% a few minutes before we were ready to pull out of the driveway.

The full charge allowed us to avoid an additional SuperCharger stop when we detoured to visit a friend in a hospital along the route.

Also minimized my wife’s range anxiety as we crossed the Chesapeake Bay Bridge-Tunnel before planned charge stop in Norfolk, VA.

Charged the car to 90% overnight, using a dryer outlet, after we arrived at Outer Banks rental.

Will probably charge to 100% to start return trip for the same reasons.