Optimum SOC

Optimum SOC

I'm sure this has been discussed, ad nauseum, but I'm new here and can't find a thread that discusses it, so please forgive me.

I have a 90D on order, and am waiting for the HPWC to be installed. My wife will be the primary OP, and her commute is about 100 miles/day.
From what I've read, a 70% SOC should be adequate, but here is my question.

Why not charge it to 100% every night? My wife may decide to go shopping (as women are wont to do) or visit her boyfriend :-) and the extra juice would come in handy.
I may have read that 100% charge is not very good for the battery, but with an 8 year, infinite mileage, who cares?

Thanks for any clarification.

luckyj | June 12, 2017

Other folks will probably go over the impact on the battery, but be aware that there are other side-effects with a battery at 100%.

For example, regen is severely limited at 100% until you discharge some of that capacity. That means the amount of "braking" from just taking your foot off the accelerator will be much less than normal. Some folks probably don't mind it, but others will get annoyed when the car acts differently to the same control inputs.

Also, the higher the SOC, the slower the charge from higher-powered chargers. So if you're out and about and happen to need a little more juice, supercharging will be slower. May not matter in most cases, but it's something to consider.

murphyS90D | June 12, 2017

Never charge to 100% unless you need the range and will be leaving within an hour of charge completion. | June 12, 2017

Your car will present a message when you set the charge limit to 100%. Doing this for an occasional road trip is OK but daily is not good idea if you wish to preserve the capacity of the battery over time as well as possible.

Charging regularly to 70-90% works well and is easier on the battery's health, skipping the details.

The loss of regen when you charge to 100%, as noted above is a good point. You quickly become accustomed to driving with one foot, minimizing the use of the brake pedal. It is unsettling when regenerative braking is not available.

MarylandS85 | June 12, 2017

Charging to 100% every night will lead to battery degradation. This is not officially covered by the battery warranty. Depending on how long you keep the car, you may regret the consequent range loss. Even if you sell the car in a few years, a savvy prospective buyer will not be willing to pay as much if the battery degradation is severe.

The 90D has a rated range of 270 miles at 100% charge. I don't know how cold it gets where you live, how hilly your wife's drive will be, or how leadlike her foot is, but your rated range would be 243 miles at 90% or 216 miles at 80%. In a worst-case scenario, if your wife likes to gun it every time, drives in crazy hilly terrain, and is driving in cold weather, she will achieve ~3/4 of these numbers (203 at 100%, 182 at 90%, 162 at 80%). Assuming her commute is 100 miles round trip, that still leaves her with at least 60 extra miles every single day (before supercharging if needed).

So the relevant questions are how far off her usual commute does your wife's boyfriend live, does he have a NEMA 14-50 plug, and/or how much stamina does he have in bed (so you can calculate how many miles she can add in the time they're together)?

Captain_Zap | June 12, 2017

I care because I expect my battery to last A LOT longer than 8 years. I'm almost 5 years in and things are looking good.

I wouldn't worry about charging to 95% daily, but I wouldn't touch 100% for anything but short periods of time and on an infrequent basis. My routine charge is between 80% and 85%.

Here is more than you will ever need to know:

judge | June 12, 2017

I suggest you charge it up to 160 each night.... Go to 100% only when you really need to.

garywillson | June 12, 2017

OK, I'm convinced. Thanks for your advice !

I might try an 80% charge for most days.

SbMD | June 12, 2017

@gary - seems like a reasonable plan. For more information, here's a link from the Owners Manual Companion thread that discussed charging and SOC.

Rocky_H | June 12, 2017

@garywillson, Quote: "I may have read that 100% charge is not very good for the battery, but with an 8 year, infinite mileage, who cares?"

Well, there's a very quick and easy answer to this. It's NOT covered by the warranty.

@Majcina kind of understates it a bit by saying, "This is not officially covered by the battery warranty."

The wording in the warranty is actually really clear and specifically excludes regular degradation from use from being covered at all. So it's a good idea to follow their recommendations to not intentionally degrade your battery.

garywillson | June 12, 2017

Thanks, Rocky_H and all !!! I've learned a lot here and on other threads !!!!!

luckyj | June 12, 2017

Wait, what just happened here? A thread that didn't degrade into nonsense and tiraids! Can we get this fixed, please? Tesla? Are you listening? I will sue everybody!

I mean uhh... Nice job, guys :)

Tropopause | June 12, 2017


Daily charging up to 90% is perfectly acceptable as notated on the Tesla 17" charging page. That is the daily maximum and will yield the most miles for your wife without concern for the battery.

vp09 | June 12, 2017

Plus One LuckyJ!

MarylandS85 | June 12, 2017

OP is the reason for the civility. He opened with self-deprecating humor and closed with an open-minded willingness to change his opinion. Kudos @garywillson

luckyj | June 12, 2017

Indeed. Hope this is a trend.

barrykmd | June 13, 2017

"A thread that didn't degrade into nonsense and tiraids"

What's a tiraid? A bandaid for tires?

Happy now? :-)

Goose | June 13, 2017

Just a side note to the comment "The 90D has a rated range of 270 miles at 100% charge."

My 90D gets 299 miles at 100% and 269 miles at 90%

AmpedRealtor | June 13, 2017

First of all, if you need the range then charge to 100% and don't worry about it. However, charging to 100% often will stress the battery and cause dendrites to form on the battery's anodes. This results in a loss of capacity over time, which will reduce range and negatively impact performance.

Tesla's 8 year, infinite mile battery warranty covers FAILURES, it does not cover loss of range due to use. Those are two completely different things. If your battery naturally loses 20% of its capacity over time because you charge to 100% every single day, you own your fate. If one or more internal modules fail, or your battery fails completely, then Tesla will replace it under warranty.

The only Model S that can be charged to 100% without experiencing accelerated degradation is the S60 w/ 75 kWh battery. That's because, with a 60 kWh artificial software limit, at 100% charge you are really only charging to about 90% or so of the battery's true capacity. The S60 w/ 75 kWh pack will also not experience the severe tapering that occurs near 100% with the other packs.

murphyS90D | June 13, 2017

My pre-refresh S90D is rated at 288 miles for 100%. I'm on my second battery and have never gotten more than 255 miles at 90% which computes to 283 miles for 100%.

jordanrichard | June 13, 2017

Tropopause +1. As Tesla refines there processes and discovers new optimum settings like the "Comfort" % for the Pano roof to open, they make changes. If my memory is correct, the original comfort setting for the pano roof for like 80%, but after a software update, that changed to 75%.

My point here is, Tesla has stuck with 90% as the recommended daily limit for years now. So it is safe to say, constant 90% charges will do no harm, even if you let it sit at that 90% SOC.

gogsee | December 1, 2018

@Goose I’ve 90D and the charge capacity has reduced to 244(90% charge) and 270(100%) charge.
It’s been 2+year that I’ve the car. How’s your battery life so far?