How long can it sit at 100%

[Llama.]

Hello all

I’m aware that it’s not good to leave the car sitting at 100%, but how long is too long?

When I go on a road trip and I do change to 100%, I would prefer to charge to full using off peak energy between 12.30 and 4.30.

I have been charging that last 10% in the hour or so before setting off, but this costs 3 times as much and the last 10% takes longer than you’d think.

If I plan to set off at 8.00 AM, how bad is it to leave the car at 100% from 4.30 AM?

Thanks

Llama.

 

[Ben_]

I wouldn’t worry about that. I wouldn’t - and don’t - leave the car at 100% for days at a time if unused, and wouldn’t recommend charging to 100% unless you’re doing a road trip. But you’re going to do no harm with the car at 100% for a few hours.

 

[Envchem]

No issue for a couple of hours and for the odd occasion.
Problem would be if you were doing it very often and leave it at that charge state for days.
Also I think i have read that the China made SR with the different battery type have no issue at all with this. You may want to double check this though.

 

[Ben_]

Cars with lithium iron phosphate (LFP) chemistries are designed to be charged to 100% and can safely be charged as such with no harm.

 

[Billbrown1982]

Yeah your totally fine on that one. As much as its "good practice" not to go full 100%, I think we have gotten ourselves into this panic state that the car is going to explode, or worse, immediately degrade the battery as soon as that dial hits 100.

I must admit its something i've been agonising over lately. I, much like yourself, only charge off peak. I do about a 60 mile commute every day and in the winter, 3 hours charging will comfortably get me back to 90%.

However, where its been getting busy at work, sometimes i'm not getting home until 2am or later and the car isn't getting the full 3 hours, so as the week progresses my soc is getting lower and lower, until towards the end of the week i'm starting to contemplate the dreaded "peak charge" or driving out of my way to use up some of those supercharger miles that are expiring in March.

I kind of want to start charging to 100 at the beginning of the week to give me a headstart throughout the week. But doing it every week, would probably, eventually, lead to "some" degradation of the battery life. Makes it a tough call.

 

[Jason71]

Yeah your totally fine on that one. As much as its "good practice" not to go full 100%, I think we have gotten ourselves into this panic state that the car is going to explode, or worse, immediately degrade the battery as soon as that dial hits 100.

I must admit its something i've been agonising over lately. I, much like yourself, only charge off peak. I do about a 60 mile commute every day and in the winter, 3 hours charging will comfortably get me back to 90%.

However, where its been getting busy at work, sometimes i'm not getting home until 2am or later and the car isn't getting the full 3 hours, so as the week progresses my soc is getting lower and lower, until towards the end of the week i'm starting to contemplate the dreaded "peak charge" or driving out of my way to use up some of those supercharger miles that are expiring in March.

I kind of want to start charging to 100 at the beginning of the week to give me a headstart throughout the week. But doing it every week, would probably, eventually, lead to "some" degradation of the battery life. Makes it a tough call.

Are you on Octopus Go. If so you could ask them to change your off peak hours.they used to offer the following. Who knows if they still do. Prices have gone up but windows may still be the same.

Option 1. Take a 3-hour Go period at 4.5p/kWh and select a start time of 20.30, 21.30, 22.30, 23.30, 00.30, 01.30, 02.30 or 03.30
Option 2. Take a 4-hour Go period at 5.0p/kWh and select a start time of 20.30, 21.30, 22.30, 23.30, 00.30, 01.30 or 02.30
Option 3. Take a 5-hour Go period at 5.5p/kWh and select a start time of 20.30, 21.30, 22.30, 23.30, 00.30 or 01.30

 

[Billbrown1982]

I am, and as much as I'm tempted to ask them to change my tariff and charging window, I'm also afraid to wake the dragon as I've only just been renewed for another year on the existing cheap rates.

 

[UkNorthampton]

Better to sit at 100% than below 20% (I seem to recall from one of the thousands of youtube videos/TMC posts I've seen).

 

[amnlinc]

Are you on Octopus Go. If so you could ask them to change your off peak hours.they used to offer the following. Who knows if they still do. Prices have gone up but windows may still be the same.

Option 1. Take a 3-hour Go period at 4.5p/kWh and select a start time of 20.30, 21.30, 22.30, 23.30, 00.30, 01.30, 02.30 or 03.30
Option 2. Take a 4-hour Go period at 5.0p/kWh and select a start time of 20.30, 21.30, 22.30, 23.30, 00.30, 01.30 or 02.30
Option 3. Take a 5-hour Go period at 5.5p/kWh and select a start time of 20.30, 21.30, 22.30, 23.30, 00.30 or 01.30

I moved to go in September just before the price increases. Shortly afterwards I enquired about moving to option 2 but was told it would mean losing my cheap rate and signing up to whatever the current go tariff is. I decided to stay put

 

[Llama.]

Yes I’m on Octopus Go.

Sorry I should have clarified that I drive a made in China M3 LR

 

[Jason71]

I moved to go in September just before the price increases. Shortly afterwards I enquired about moving to option 2 but was told it would mean losing my cheap rate and signing up to whatever the current go tariff is. I decided to stay put

I moved to a 3 hour period from 8:30pm back in march and you are right it did seem to re-set my year fixed rate. At the time though the old and new rates were the same so it did not worry me and obviously ended up locking in my cheap rate for another year but yes I think if you are not on the current rates asking for it now is probably not a good idea

 

[Mr H]

That 10% is roughly (for maths sake) 7KwH, so at go rates will cost 35p and at normal rate will cost £1.05 a difference of 70p which in the cost of a 50k car is not worth worrying about.

 

[rotor2k]

Unless you're heading to darkest Wales (very few superchargers I hear) it is unlikely you need to set off with 100% anyway. As long as you can comfortably make it to a supercharger I wouldn't bother going over 90-95%.

 

[Jason71]

That 10% is roughly (for maths sake) 7KwH, so at go rates will cost 35p and at normal rate will cost £1.05 a difference of 70p which in the cost of a 50k car is not worth worrying about.

The premise that "if you can afford a 50K car you can afford XYX" comes up a lot on here but it is a flawed one.
Yes it does apply to some but for others the 50K car may be the first new car they have ever bought and they have done the "Tesla Stretch" to do it so potentially every penny counts.

Your maths are correct though so if you do it every weekday that is £180 a year.
octopus go latest rates are 30.7/7.5 so now that £180 becomes £422.
I assume that is just a middling bottle of wine to you but to others its worth saving. So I think its a very fair question.

Having said all that I own mine so I try to look after the battery. Before a long journey I charge to 90% over night then put back on charge an hour before leaving. Yes it costs a little more and it does not get to 100% but it heats up the battery so the car is more efficient when I do leave and while I might only get to say 96% the last 4% does not give you 4% more range anyway since you get no regen when the battery is full which reduces efficiency and I find disconcerting.

 

[rotor2k]

Having said all that I own mine so I try to look after the battery. Before a long journey I charge to 90% over night then put back on charge an hour before leaving. Yes it costs a little more and it does not get to 100% but it heats up the battery so the car is more efficient when I do leave and while I might only get to say 96% the last 4% does not give you 4% more range anyway since you get no regen when the battery is full which reduces efficiency and I find disconcerting.

That's not a bad way of doing it...

 

[Mr H]

The premise that "if you can afford a 50K car you can afford XYX" comes up a lot on here but it is a flawed one.
Yes it does apply to some but for others the 50K car may be the first new car they have ever bought and they have done the "Tesla Stretch" to do it so potentially every penny counts.

Your maths are correct though so if you do it every weekday that is £180 a year.
octopus go latest rates are 30.7/7.5 so now that £180 becomes £422.
I assume that is just a middling bottle of wine to you but to others its worth saving. So I think its a very fair question.

Having said all that I own mine so I try to look after the battery. Before a long journey I charge to 90% over night then put back on charge an hour before leaving. Yes it costs a little more and it does not get to 100% but it heats up the battery so the car is more efficient when I do leave and while I might only get to say 96% the last 4% does not give you 4% more range anyway since you get no regen when the battery is full which reduces efficiency and I find disconcerting.

Your £180 a year is moot, if you're doing it every day then a 70p saving will be the least of your worries. I own mine too and also look after the battery which is probably pointless as it'll be replaced before the warranty expires, it will be good for the next owner though.

 

[drtimhill]

Hello all

I’m aware that it’s not good to leave the car sitting at 100%, but how long is too long?

When I go on a road trip and I do change to 100%, I would prefer to charge to full using off peak energy between 12.30 and 4.30.

I have been charging that last 10% in the hour or so before setting off, but this costs 3 times as much and the last 10% takes longer than you’d think.

If I plan to set off at 8.00 AM, how bad is it to leave the car at 100% from 4.30 AM?

Thanks

Llama.

The battery is really not that fragile .. in fact its nothing to do with KEEPING the car at 100% so much as charging it to that level. And even then you can do it safely many times before it will have any impact at all. Charge the car to 100%, and dont fret about it

 

[Irata]

Occasional charging to 100% by 4:30am and leaving at 8am will have no impact on the battery.

Charging the car everyday to 90% will have a greater impact overall.

Having said that, in one year my degradation at 100% is just 4 miles loss, yet I've charged to 100% about 5 times now and it sat 5 hours each time. Also the first 6 months I needed a daily 90% charge.

Degradation isn't an overnight thing, it's a months and years thing.

 

[Roy B]

in fact its nothing to do with KEEPING the car at 100% so much as charging it to that level.

I don't think that's true. Keeping a lithium ion battery for long periods of time at either very high or very low levels of charge is non-optimal - at least for most chemistries (LFP clearly seems to be an exception here). Of course, what constitutes very high and very low, what constitutes long periods, and how much difference it makes

 

[MrT3]

LFP clearly seems to be an exception here

I’m not so sure. There isn’t a lot of research out for LFP at the moment and it probably isn’t affected as much but there will be something. Tesla want you to charge to 100% at least weekly to keep the BMS calibrated, not for the health of the cells.