Charge Daily or Charge as needed?

[digitaltim]

Like a cell phone. I'm not real good with iPhones.

Like a mobile is my preference...

Why Do We Use The Term Cellular Phone Instead of Mobile Phone?

PS - I charge to 90% every chance I can get and always start a 100%/range charge an hour or so before I start any long distance jaunt...

58k miles and counting...

 

[brianman]

Like a mobile is my preference...

Noted. I'd probably go with "mobile phone" though, as to me "mobile" is an adjective that applies to many things.

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Somewhat related observation...

My daily commute (combined both ways) is ~30 miles on a "boring" work day. I have left my slider at the default (originally 93%, now 90%) since taking delivery of the vehicle.

My 90% charge has been 221 rated miles for months. Then I took a trip through a few states in the last few weeks. My 90% charge is now 223 rated miles.

I suspect it's more about temperature than about balancing, but it was an interesting development so I thought I'd mention it.

 

[David99]

Tesla specifically recommends to keep the car plugged in. This doesn't mean you should keep it fully charged at all times, but it is good for the battery if the car is plugged in.

As we have learned from many studies and tests, higher state of charge makes a battery age quicker. Higher temperatures also increase aging. That means it's good to keep the battery at a lower state of charge and only charge it in time before we need it. On a daily basis this would mean to only charge to a level that you will need (plus some buffer) and time the charge process so it just finishes the moment you plan on using your car.

 

[dtich]

i charge to 85% at 1am @24A (on a normal day this allows plenty of time to charge to 85% within the low usage hours of 12-6a; this also reduces wear from heat while minimizing the amount of time the car sits at maximum soc); usually i charge every other day with the determining factor being whether or not i get close to 50%--if i'm not close to 50 and the next day isn't an especially big drive day, i don't charge. mostly don't get under 50% soc on normal days, as planned... and when i'm not driving it for a week or more i set it to 50% and leave it plugged in.

i feel pretty confident that this method balances concerns for the health/longevity of the battery with my driving needs and never leaves me without a car; i don't ever not do anything because of my charging habits however, if i need a full charge i do a full charge.

 

[Keith Gilabert]

How many miles can you get with a 15 minute charge or is there a minimum amount charging required.

Thanks,

Keith

 

[TexasEV]

How many miles can you get with a 15 minute charge or is there a minimum amount charging required.

Thanks,

Keith

The answer is it depends. A 50A 240V circuit (NEMA 14-50) which is what's recommended for home charging will give about 7 miles range in 15 minutes. A typical J1772 public charging station of 30A will give 4 or 5 miles in 15 minutes. If it's a 120V outlet, don't bother. Look at the charging page on the Model S website for details.

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i charge to 85% at 1am @24A (on a normal day this allows plenty of time to charge to 85% within the low usage hours of 12-6a; this also reduces wear from heat while minimizing the amount of time the car sits at maximum soc); usually i charge every other day with the determining factor being whether or not i get close to 50%--if i'm not close to 50 and the next day isn't an especially big drive day, i don't charge. mostly don't get under 50% soc on normal days, as planned... and when i'm not driving it for a week or more i set it to 50% and leave it plugged in.

i feel pretty confident that this method balances concerns for the health/longevity of the battery with my driving needs and never leaves me without a car; i don't ever not do anything because of my charging habits however, if i need a full charge i do a full charge.

You're using more energy that way so it's costing you more. Tesla has said the car charges more efficiently at 40A. There is no evidence that charging at lower amps "reduces wear from heat".g

 

[Barry]

Battery life is usually rated by the number of charge/discharge cycles. It seems to me that it would be better NOT to plug in every night if you're doing a short work commute. Am I missing something?

 

[andrewket]

i charge to 85% at 1am @24A (on a normal day this allows plenty of time to charge to 85% within the low usage hours of 12-6a; this also reduces wear from heat while minimizing the amount of time the car sits at maximum soc); usually i charge every other day with the determining factor being whether or not i get close to 50%--if i'm not close to 50 and the next day isn't an especially big drive day, i don't charge. mostly don't get under 50% soc on normal days, as planned... and when i'm not driving it for a week or more i set it to 50% and leave it plugged in.

i feel pretty confident that this method balances concerns for the health/longevity of the battery with my driving needs and never leaves me without a car; i don't ever not do anything because of my charging habits however, if i need a full charge i do a full charge.

24A is less efficient than 40A, so you're wasting energy and increasing your costs. 40A=> is most efficient. The difference between 40A and 80A is negligible.

 

[jerry33]

Battery life is usually rated by the number of charge/discharge cycles. It seems to me that it would be better NOT to plug in every night if you're doing a short work commute. Am I missing something?

Charge/discharge cycles means 100% to 0% (of course, the car doesn't actually let you do that). The smaller the cycle, the longer the battery life. So to put some "pulled out of the air" numbers on it, if a 0-100 cycle allows 500 cycles, a 10-90 would be 1500, and a 20-80 might be 6000. The shorter the cycle, the more cycles you can get out of it, and it's not linear.

 

[steve841]

Charge/discharge cycles means 100% to 0% (of course, the car doesn't actually let you do that). The smaller the cycle, the longer the battery life. So to put some "pulled out of the air" numbers on it, if a 0-100 cycle allows 500 cycles, a 10-90 would be 1500, and a 20-80 might be 6000. The shorter the cycle, the more cycles you can get out of it, and it's not linear.

Damn good explanation.

 

[David_Cary]

The answer is it depends. A 50A 240V circuit (NEMA 14-50) which is what's recommended for home charging will give about 7 miles range in 15 minutes. A typical J1772 public charging station of 30A will give 4 or 5 miles in 15 minutes. If it's a 120V outlet, don't bother. Look at the charging page on the Model S website for details.

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You're using more energy that way so it's costing you more. Tesla has said the car charges more efficiently at 40A. There is no evidence that charging at lower amps "reduces wear from heat".g

Well since heat damages batteries and charging faster creates more heat, there is really no doubt that charging slower helps with battery life. There is "no evidence" for a lot of things but they are felt to be true based on studies on other batteries. Is it significant? - I'm not sure anyone really knows. Sure Tesla uses a TMS to help maintain temperatures but that doesn't mean it keeps the battery at the absolute best temperature for longevity. It balances many things. The battery most likely would last longest at 40 degrees but the TMS certainly doesn't try to keep the battery there.

Heat kills batteries. Charging heats batteries. Charging faster heats more. Those are irrefutable facts.

Is it worth 10% overhead loss to save 1% of battery life? Hard to say. And who knows if those numbers are even close to reality.

 

[TexasEV]

Well since heat damages batteries and charging faster creates more heat, there is really no doubt that charging slower helps with battery life. There is "no evidence" for a lot of things but they are felt to be true based on studies on other batteries. Is it significant? - I'm not sure anyone really knows. Sure Tesla uses a TMS to help maintain temperatures but that doesn't mean it keeps the battery at the absolute best temperature for longevity. It balances many things. The battery most likely would last longest at 40 degrees but the TMS certainly doesn't try to keep the battery there.

Heat kills batteries. Charging heats batteries. Charging faster heats more. Those are irrefutable facts.

Is it worth 10% overhead loss to save 1% of battery life? Hard to say. And who knows if those numbers are even close to reality.

We charge almost an order of magnitude faster at superchargers than at 40A, and that's not killing the battery, so it's highly unlikely there would be a significant difference in battery life between 24A and 40A. The OP may feel better doing it that way but he's treating himself, not the car.

Just enjoy the car, charge to 100% only when you need to, and let the battery management system manage the battery.

 

[In2oil]

What are your best practices?[/QUOTE]

Here s my case, I work out of town and I'm unable to drive my tesla to work. Therefore my tesla get parked in the garage for weeks without use, sometimes longer.(2-3weeks). One very knowledgeable owner here in Calgary told me to keep the battery at 50percent and plugged in. My home charger is wired with. A. Nema 14-50 40a, I get about 52k. Per hour charge.

my question is, would It be better to charge to 80-90 percent and leave it plugged in? Or continue what I am doing. Is it normal that my tesla appears to never really go to sleep. My battery does lose some 10km of charge every day? I think the charger (I leave it plugged in) recharges the battery when the charge gets too low.

 

[djp]

my question is, would It be better to charge to 80-90 percent and leave it plugged in?

You're doing the right thing for storage. Lower SOC is easier on the battery if you're not driving the car. The SOC will slowly drift down to 50%, then the charge cycle will hold it there.

 

[ACDriveMotor]

Charging at 10kw is not worse than driving at 40kw. Discharging batteries heats them. @davidcary curious to know if you keep driving below 10kw to minimize battery damage?

I don't because the BMS will protect the battery whether charging or discharging.

 

[TexasEV]

You're doing the right thing for storage. Lower SOC is easier on the battery if you're not driving the car. The SOC will slowly drift down to 50%, then the charge cycle will hold it there.

Agree, Tesla has said for long term storage, set at 50% and keep plugged in.

 

[dtich]

24A is less efficient than 40A, so you're wasting energy and increasing your costs. 40A=> is most efficient. The difference between 40A and 80A is negligible.

technically, yes, but almost all my household electricity comes from solar, so my priority is not pure efficiency but stress on the battery. and i charge at that time of day to be a good neighbor and use current when it is least impactful on the whole delivery system (grid). i don't remember the numbers (no doubt someone will point them out ) but i don't believe the lessening of charging efficiency from 40 to 24A is terribly big... i could be wrong. in any case, this method makes sense for my scenario. ymmv.

 

[David_Cary]

These debates have happened before and I'm sure will happen again. Of course using the go pedal heats the battery a lot. But at least that gives some tangible benefit. Short acceleration bursts are of course short. And driving at 70 mph doesn't exactly allow for local heat buildup.

Charging fast if you are just doing it overnight gives no tangible benefit for lots of people (some benefit from small windows of off peak). There is some small efficiency difference.

Sure the BMS handles extremes. Like supercharging. But the BMS does not maintain perfect temps. Just because someone wants to absolutely optimize battery life and another is happy trusting the car to do the right things doesn't make either choice wrong.

If you look at temps the BMS uses and then look at optimal temps for lithium batteries, you will see compromises were made.

The number one resale factor for an old Model S will probably be battery degradation. Is it any surprise that some people want to optimize that? Given what we have seen so far and the declining price of batteries, it may not be worth obsessing over.

Then of course there are other grid related reasons to chill the charging speed also.

 

[jerry33]

What are your best practices?

Here s my case, I work out of town and I'm unable to drive my tesla to work. Therefore my tesla get parked in the garage for weeks without use, sometimes longer.(2-3weeks). One very knowledgeable owner here in Calgary told me to keep the battery at 50percent and plugged in. My home charger is wired with. A. Nema 14-50 40a, I get about 52k. Per hour charge.[/QUOTE]

You're doing it right. Charge to 50% except on the days when you drive it.

 

[scaesare]

My work commute is ~65miles round trip.... and I rarely need to drive more than 25 miles in the evening.

So I have Visible Tesla scheduled to set my weekday charge limit at 60% during warm months, yielding 150 miles of rated range. In colder months I bump this to 70% to allow for some cold temp loss.

On weekends I might drive anywhere from 0 to 200 miles in a day, so VT is scheduled to set me at 90% for those days.

Plug in every night. As matter of fact, VT will send me a note at 11pm if my car is NOT plugged in.