How low is too low?

[redmg4]

Have an MG 4 long range. How low is it okay to let the battery go in every day use, and occasionally?

 

[webhiker]

Depends on your views.
My view is occasionally 0.5% (you need to get home, right?)
Every day use I start charging around 15% (but I charge at a parking lot overnight. I can't have a home charger)

 

[Rolfe]

It's more a question of how low you should leave the car sitting at. If you consider best practice for the top of the scale, not leaving the car sitting for days on end above 80%, at least not frequently, and also apply that to the bottom 20%, you won't go far wrong.

Operate the battery routinely between 20% and 80%. If you charge above 80% then drive the car fairly soon afterwards so that it goes below 80%, don't leave it sitting up there. If you run the battery below 20% then charge up soon afterwards, don't leave it sitting around down there.

Use the charge you have to get where you're going, though. It won't do any harm. On a long trip you can roll into a charger on your last electron if you have a cool enough head, and charge to 100% if you have the patience and there isn't a queue of other drivers wanting to lynch you.

 

[webhiker]

What Rolfe said

 

[fnegroni]

Have an MG 4 long range. How low is it okay to let the battery go in every day use, and occasionally?

Occasionally, any level above zero.
Daily, I would charge at anything below 50%.

 

[DerekH]

It's more a question of how low you should leave the car sitting at. If you consider best practice for the top of the scale, not leaving the car sitting for days on end above 80%, at least not frequently, and also apply that to the bottom 20%, you won't go far wrong.

Operate the battery routinely between 20% and 80%. If you charge above 80% then drive the car fairly soon afterwards so that it goes below 80%, don't leave it sitting up there. If you run the battery below 20% then charge up soon afterwards, don't leave it sitting around down there.

Use the charge you have to get where you're going, though. It won't do any harm. On a long trip you can roll into a charger on your last electron if you have a cool enough head, and charge to 100% if you have the patience and there isn't a queue of other drivers wanting to lynch you.

Perfect answer without all of the paranoia on charging to 100%. . Probably the only thing I would add is where possible and for the long term health of the battery, charge at the slowest speed that works in your situation, again without being paranoid. Constant usage of fast DC charging over slower charging methods, puts more stress over the long term on battery cells.

 

[Rolfe]

That's the received wisdom, but I keep hearing about exceptions. The Tesla that went 420,000 miles before the battery flagged a fault, mostly on superchargers as it was only five years old at the time. Lots of Teslas being supercharged constantly and not having a problem. Someone on Twitter the other day saying the worst battery degradation he ever saw was in a Leaf that had never seen a DC charger in its life. (Might have been constantly cycled between 80% and 100% on AC though, that kills Leaf batteries, indeed any NMC battery.)

I think the take-home message is to follow the recommendations for your battery type without being obsessive or paranoid about it. If you do low mileage, run NMC batteries between 20% and 80%, but don't worry about charging to 100% or running down as low as you have the nerve for if you're driving a long distance. Favour AC charging whenever possible, but don't hair-shirt if you do use a DC charger. Try to balance at 100% on AC every few weeks, and try to do a <10% to 100% AC charge a couple of times a year if you can.

But don't stress about it, and the worst that's likely to happen if you don't balance or do the long charge regularly is a temporary loss of range and your GOM landing you in it when you do run low, by suddenly realising it's lower than it thought and doing a massive correction whereby you suddenly have 20 miles less than you thought you had. All fixable by actually doing the thing you had neglected to do.

With the LFP, charge to 100% as often as you like and let it sit there, it won't mind. In fact it likes to go to 100% and balance often. And favour AC charging when you can, and do that long charge a couple of times a year. What could go wrong?

Well, I'll tell you what. You can have the long charge well underway on a granny lead, anticipating finish by the following afternoon, when you hear that there is going to be the best aurora in 20 years later that night, chuck all the plans in the bin, unplug at 32% and go aurora-watching.

 

[siteguru]

With the SR you mean, not SE (as there's also an SE LR).

 

[Rolfe]

Jings, I edited that so fast, too...

 

[Ian Key]

Another factor is the battery management systems have improved as manufacturers have learned more about how the batteries behave. The first Leafs for all intents and purposes didn't have a management system so their batteries got stressed during charging whereas the more modern EVs systems are much better at controlling the speed and battery temperature during charging.

 

[Bricktop X PWR]

99% of my charging is fast.

I balance with fast to 97% then slow for the remaining, once a month.

The exact way I do it is.....

Fast to 97%, as this is when it stops charging.
Drive to a local 7kw car park charger near me.

Battery now at circa 87%

The 7kw charger will go to 100% where the car then sits for anything up to an hour, balancing.

Meanwhile I am in the Station Inn, having lunch and a pint. (obvs)

I have no facility to balance any other way.

My car sits at circa 80% most of the time when at home.

In normal week to week operations she rarely gets below 20%

I lose zero sleep about my batterys health or longevity, but do look after it the best I can, with the knowledge I have, given my personal situation.

It really won't be my problem however it turns out.

After a recent balance and reset I had 250 miles of GOM.
More than I started with!

I can see myself in the car for a maximum of 5 years, (probably much less if my previous history is anything to go by) so will never find out the condition of the battery at the 7 year point or the value of the warranty for the battery, should it be required.

 

[Rolfe]

99% of my charging is Fast.

I balance with fast to 97% then slow for the remaining once a month.

I have no facility to balance any other way.

My car sits at circa 80% most of the time.

In Normal week to week operations she rarely gets below 20%

I lose zero sleep about my batterys health or longevity, but do look after it the best I can, with the knowledge I have, given my personal situation.

It really won't be my problem however it turns out.

After a recent balance and reset I had 250 miles of GOM.
More than I started with!

I can see myself in the car for a maximum of 5 years, (probably much less if my previous history is anything to go by) so will never find out the condition of the battery at the 7 year point.

Sounds eminently sensible.

 

[georgeOfCentralCoast]

Note this does not apply to the 51kWh excite, ignore this if you have one of these.

Currently the 66kWh and the 71kWh models have a nickel manganese cobalt battery based lithium ion chemistry. If this changes, the advice below may not apply.

My two cents as an ADHD and OCD electrical engineer my research for the best battery life is to do the following:

Don't charge above 80% unless you need to, peace of mind and range anxiety are fine reasons in my opinion, but be smart about it. Just before a long trip and when the temperatures are cooler go for it. Over 30 degrees in Summer, take extra care, charge past 80% just before you need it, not days before.

Try to keep it between 70% and 30%, if you are a fast charger user, if you see one and you have a few minutes use it top off up to 70%, if a charger is conveniently located and priced, anything is better than waiting. Otherwise plug it at home every day and limit to 70% unless you need the range for the next day. The smaller the cycle, the better for your battery.