What should my ideal charge percentage be?

[TexasEV]

Yes it’s been addressed here dozens of times, and it’s in the owners manual. Plug it in. You could set the charge down to 50% (recommended for long term storage) but for just 3 weeks it’s not that important.

A connected Model S is a happy Model S

 

[vrykolas]

This has likely been addressed previously, but I didn't see it. We are going way for three weeks without the Model S. Is it better to leave it on the charger or just let it sit in the garage without being plugged in. I generally charge to 70-75%.

Many places recommend storage to set at 50% and keep plugged in.

 

[Vern Padgett]

I would say that this topic has been addressed more than dozens of times.

I'd also say that there is no consensus beyond keeping it between 10 and 90 percent charged.

The advice for "keeping it plugged it" is conflicted by the manufacturer's interest in avoiding any batteries discharged by long periods of not being plugged in, and resultant customer outrage.

The possible if minor cost of having all owners overcharge is less than the possible cost of having any one customer fail to charge adequately.

When we evaluate a source's credibility, we examine the expertise and the trustworthiness of the source. Tesla is certainly expert in its battery charging advice. On the second dimension, they do have a vested interest in never encountering a customer whose battery discharged from neglect, hence, probably, the advice to charge more than needed.

There is the likely definitive lecture by battery architect and chemist Professor Jeff Dahn

at 73 minutes. Watch this and pay attention please before asking us more about how long to charge your batteries.

If I were leaving for a long time, longer than 3 weeks, I would plug in my Ss and set them for some level between 30 and 70 percent charge. Three weeks, not to worry.

I could be wrong.

 

[TexasEV]

Sorry, but no one needs to watch a 73 minute idea to find out if he should plug in the car while it’s not being used for weeks. Don’t make this more complicated than it needs to be. The answer is YES. It’s not a matter of conflicting interests or anything like that. It’s in both the owner’s and Tesla’s interest to keep the car plugged in.

State of charge is another matter. 50% for long term storage (months) but 3 weeks isn’t long term storage. The owner said he usually charges to 70%. There’s no practical difference.

 

[FlatSix911]

Interesting reading from Electrec ... Are you killing your lithium batteries?
Here is a quick summary for those who do not want to watch a 1hr video
.
How to make Li-ion batteries last longer
The first thing you should do is to avoid letting your battery get hot. Fortunately, many electric vehicles go part of the way there. Tesla’s vehicles and the Chevy Bolt/Volt all use active cooling to keep the battery from overheating, though the Nissan Leaf relies on passive air cooling to keep the battery cool, making battery heat an even larger factor for those vehicles.

The bigger heat issue that you have more control over is heat during charging. Even for cars with active battery cooling, the battery still heats up considerably during charging, especially when charging at high rates or supercharging. While supercharging is convenient when you need to get back on the road quickly, it is terrible for battery life if performed often. To make your battery last as long as possible, you should try to charge at lower rates, which keeps the battery cooler and happier. A longer charge each night is much better than supercharging over lunch each day.

Next, you should aim to charge to lower levels when possible, especially if the car will be resting for a long period of time. While it may be comforting to see your battery meter read “100%”, your battery will be anything but comfortable. Jeff Dahn states that charging to a level below 100% can have a large impact by reducing the rate of degradation of the battery.

Most people don’t use their entire electric vehicle battery pack capacity every day, and rarely have the need to charge all the way to 100%. By charging a lithium-ion battery to 80%, the lifetime of the battery can be as much as doubled, according to Grin Technologies. This Canadian company performed such tests while developing an adjustable charger designed for electric bicycles and other light electric vehicle batteries.

It is important to note that the most damage from high charge levels comes from when the battery rests at such high levels for long periods of time. I’ve heard of many people who freak out after learning about the effect of high charge levels, with some swearing off 100% charging forever.

But 100% charging isn’t a big deal in small doses. If you are planning a long trip and will be heading out shortly after you finish charging, a 100% charge will have very little impact on your battery’s lifespan. However, if you will be leaving your battery unused for many days or weeks, a charge level of between 30-60% is much healthier for the batteries over the long-term.

 

[Fiver]

If I were leaving for a long time, longer than 3 weeks, I would plug in my Ss and set them for some level between 30 and 70 percent charge. Three weeks, not to worry.

Considering you can't set the charge limit for your Tesla below 50%, that's your baseline.

When leaving the car for a long time I set the limit to 50% and plug it in. It slowly will vampire drain down to 50% from whatever it was at when I left, and then it will charge periodically to maintain 50%. When I am heading back from wherever I was, I'll bump the charge limit back to 80 or 90% via the phone app so the car is ready when I return home.

 

[Zooomer]

Since temperature is such an issue, does it make sense to target a higher SOC in the winter than summer?

 

[Fiver]

Since temperature is such an issue, does it make sense to target a higher SOC in the winter than summer?

Tesla's have active heating and cooling on the pack, so while temperature does play into it a bit, you don't have to worry about it as much compared to the Nissan Leaf that has no thermal management.

If anything in the winter I will charge less then needed, and then about an hour before I leave I bump up to whatever charge I need for the day to help warm the pack before departure.

In the summer I just let er rip, but I don't live where it gets super hot, and I don't park outside if possible.

 

[Fiver]

I should add, the comment above is about being plugged in. Obviously if you are in some remote area without a plug (parked, skiing for the day where it's really cold) then I would charge a little higher then normal as when you leave to drive home the pack heater will come on, but will be powered by the battery, hurting range. If it's cold, and you can plug in, do it. That lets you recharge the pack as it uses power to heat up the battery. Newer versions of the app will even let you pre-heat the pack to driving temps if it's super cold, this should be done while plugged in ideally. Pre-heating the pack while not plugged in basically sucks a lot of juice out of the battery.
The only real reason to pre-heat the pack while not plugged in is if you know you are leaving the cold area and driving to a nearby supercharger or fast charger. If the pack is too cold it will take awhile for you to get the pack up to temp, and the pack will not charge at a fast rate when cold. Pre-heating the pack off the battery will allow you to quickly supercharge at a normal rate, getting you back on the road quicker.

Last year I was up snowboarding at Jackson Hole. it wasn't even really cold (maybe 25-35F) but the car sat unplugged for 3 days. I drove from the resort to the JH supercharger (about a 15 minute drive @ 50mph) and it took almost 40 minutes for the pack to warm up enough to start supercharging at a reasonable rate. I've read of much worst situations where people were stuck at superchargers with frozen packs waiting for it to warm up enough to take a charge. Oddly plugging into a 40-60amp AC charger seems to get the pack to warm up quicker initially before moving to a DC fast charger.

That, or if you have enough juice, drive around all fast like Bjorn to warm the pack up quickly before supercharging.

 

[arnis]

Tesla's have active heating and cooling on the pack, so while temperature does play into it a bit, you don't have to worry about it as much compared to the Nissan Leaf that has no thermal management.

Again and again. Same repetitive incorrect story. Tesla's battery temperature fluctuates between -15*C and +50*C. Same with Leaf.
Thermal management pretty much doesn't change anything. What is the main difference is the chemistry.
Leaf chemistry loves cold. Tesla chemistry loves warm. And I really mean it.
Tesla is crap in cold weather. It doesn't charge AT ALL if battery is cold.
Leaf is crap in warm weather. It degrades very fast when it is hot outside.
Leaf works exceptionally well with cold pack. -5*C...25*C it's perfect.
Tesla works well will warm pack. +10*C...+50*C


The warmer it is, the faster battery degrades when it is heavily charged. No matter what EV.
In case of Tesla, degradation is slower in any temperature, though still faster when hot.

 

[Fiver]

Tesla is crap in cold weather. It doesn't charge AT ALL if battery is cold.

Can you elaborate on this? I've had the car sitting overnight in 0F weather, and gone to plug it into a 48amp 208v charger and it sucks up the juice. The only time I've seen it not want to take a charge is when it's trying to DC fast charge while cold.

 

[gavine]

The only real reason to pre-heat the pack while not plugged in is if you know you are leaving the cold area and driving to a nearby supercharger or fast charger.

Or if you're staying at the top of a mountain and will be driving downhill the next morning. A cold pack will have no regen, but a warm-pack will. So, it's probably still worth pre-heating from the battery if you can't plug-in. This will save energy and the brake pads.

 

[arnis]

Can you elaborate on this? I've had the car sitting overnight in 0F weather, and gone to plug it into a 48amp 208v charger and it sucks up the juice. The only time I've seen it not want to take a charge is when it's trying to DC fast charge while cold.

The fact that there is draw doesn't mean battery is charging. 6kW heater can more than household plug provides.
If Tesla's pack is below 0*C it doesn't accept charge at all AFAIK, that includes regen (same as charging).
Ambient temp doesn't matter. Hot pack takes ages to cool down, especially on dry and calm night.

 

[vinko]

Thank you everyone for these valuable information. Especially those from experienced owners. I currently charging about 80%, but after reading this I may change that to 60%. Since I live in Macau with only one Supercharger location.

By the way, how can one tell the health of the battery? @djp said his roster kept is capacity after three years. Are you guys simply speaking of how much range you get? Or is there a third party app you can use to check?

 

[djp]

@vinko - on the Roadsters we have access to the log files and service menus so we can directly read the Calculated Amphour Capacity (CAC). For the Model S you'll need to rely on the displayed range. My Roadster is now eight years old and the battery capacity is at 97% of original, I think both the cool Canadian climate and charging to 60% have helped.

 

[ucmndd]

been contemplating this lately, I have a regular commute that uses ~60% SoC of my 75 RWD battery. Wondering if 90 -> 30% or 80 -> 20% is better.

 

[Fiver]

been contemplating this lately, I have a regular commute that uses ~60% SoC of my 75 RWD battery. Wondering if 90 -> 30% or 80 -> 20% is better.

I'm going to say it's 6's. Charging to 90% is fine, as the majority of the day you are going to be lower then that, and time at SoC has as much to do as age of the battery.

Start the day at 90%, get to work around 55%, it sits there at 55% (which is just right), and then you get home with 30%. Personally I'd low and slow charge so it hits 90% around when you leave again in the AM. It won't be sitting at 90% for days at a time, just a few hours. But really leaving it at 90% isn't terrible if you are actively using the car. I'd just set the limit lower if you aren't going to be driving for a few days, then bump it up to 90% with the phone app a few hours before you leave.

 

[DougIngraham]

been contemplating this lately, I have a regular commute that uses ~60% SoC of my 75 RWD battery. Wondering if 90 -> 30% or 80 -> 20% is better.

70%->10% is better for a couple of reasons. If you charge at a Super Charger your charge time will be less by around 10 to 15 minutes. The worst wear on the battery comes from going to high states of charge and leaving it there. The next worst thing you can do is leave it at empty for an extended period. My normal charge limit is 60% and I have lost ~1.5 mile (258 to 256) of indicated range in the 2.5 years and 50000 miles I have had the car. For a single event it probably doesn't matter where you set it but since you do this daily I would set the slider so you have adequate range at the bottom to cover an unexpected event. 10% for me would typically be 25 miles but in adverse conditions (rain, cold temps, strong headwind) you might want more than that. And there is buffer below 0% as demonstrated by several people on You tube. But I would never depend on that as having to use it would be extremely poor planning.

The question I used to get asked most often was "How far does it go?" Lately it is "Where do you charge if you run out?" The answer to this is running out is not likely if you use the NAV system as it will nag you to slow down. But you can charge at any normal wall outlet. I don't know why this surprises them. Running out is bad planning and it doesn't matter if it is ICE or EV. Note: wall outlets are usually closer than filling stations.

 

[Fiver]

And there is buffer below 0% as demonstrated by several people on You tube.

There are also many videos showing no buffer below 0%, in fact some people have had the car shut down even when showing above 0%.

Can't speak for the Model 3, but for S & X 0% means 0% unless your battery is out of calibration. Yes there still is power in the car at 0%, but it's not for driving, it's a 4kWh buffer to prevent the car from draining to the point where serious damage would happen to the battery.

If you somehow can drive below 0%, you should charge up to 100% and then drive it down again, there's no way once the battery is calibrated you will be able to drive below 0% a second time.
Telling people they have some secret buffer they don't have is only going to get people trapped on the side of the road pissed off at Tesla because they thought they had some extra driving buffer that doesn't exist.

And before you go saying "Elon tweeted about it", he meant the buffer to protect the battery, not a buffer to drive on.

There's no point in being able to drive on the safety buffer, it would completely defeat the purpose of having it and also would cause your battery to get trashed pretty quick.

I will note this applies to S & X, I can't speak for the Model 3, but we aren't talking about Model 3 here.

 

[gavine]

70%->10% is better for a couple of reasons. If you charge at a Super Charger your charge time will be less by around 10 to 15 minutes. The worst wear on the battery comes from going to high states of charge and leaving it there. The next worst thing you can do is leave it at empty for an extended period. My normal charge limit is 60% and I have lost ~1.5 mile (258 to 256) of indicated range in the 2.5 years and 50000 miles I have had the car. For a single event it probably doesn't matter where you set it but since you do this daily I would set the slider so you have adequate range at the bottom to cover an unexpected event. 10% for me would typically be 25 miles but in adverse conditions (rain, cold temps, strong headwind) you might want more than that. And there is buffer below 0% as demonstrated by several people on You tube. But I would never depend on that as having to use it would be extremely poor planning.
.

One thing to note is that driving the car while at a low SOC can be bad for the battery, mainly under hard acceleration. So, under 20%, it is advisable to go easy on the pedal. For that reason, I would advise against going-down to 10% often...unless you don't mind light acceleration.