EV battery management

MX5huggy

Keep_pedalling said:

Ebe_Scrooge said:

I've got to say, this all seems like an awful faff.  A good old petrol or diesel engine has none of these problems - fill up the tank and off you go

Home charging is no more complicated than charging your tooth brush up when it gets low on power. 

It’s simpler, the wife has never unplugged the car to use the hairdryer. 

Ganga

MX5huggy said:

Keep_pedalling said:

Ebe_Scrooge said:

I've got to say, this all seems like an awful faff.  A good old petrol or diesel engine has none of these problems - fill up the tank and off you go

Home charging is no more complicated than charging your tooth brush up when it gets low on power. 

It’s simpler, the wife has never unplugged the car to use the hairdryer. 

Can you drive off with the charger cable still attached or does it eject from the car if driven off ?

BOWFER

Ganga said:

MX5huggy said:

Keep_pedalling said:

Ebe_Scrooge said:

I've got to say, this all seems like an awful faff.  A good old petrol or diesel engine has none of these problems - fill up the tank and off you go

Home charging is no more complicated than charging your tooth brush up when it gets low on power. 

It’s simpler, the wife has never unplugged the car to use the hairdryer. 

Can you drive off with the charger cable still attached or does it eject from the car if driven off ?

No, in the Leaf anyway.
It won't let you select D or R with the cable connected.
Annoyingly, it will let you drive with the charge flap unlocked.
It's easy to accidentally press the 'flap' button on the key fob, which will release the flap and nothing to alert the driver and you can't see the flap at the end of the bonnet.
So you're unaware until you get a speed when it will pop up itself under wind pressure like a wee air brake.
Doesn't do any harm , just looks silly to anyone else around you.

[Deleted User]

Petriix said:

Ignore the ignorant posts from people who tell you not to worry about it. There is a wealth of evidence that support your thoughts.

There are two main factors in battery degradation: time and use.

Calendar degradation is inevitable but can be minimised by keeping the battery as close to 50% state of charge as possible and keeping it as cool as possible. However, the colder it is (below the optimal 23 degrees C) the less efficient the battery will be at its primary purpose of storing and releasing energy.

Damage over time will be more significant the closer it is to the extreme ends of the voltage range. The BMS will protect it from the worst (but not all) of this.

It's fairly sensible to keep it parked in the shade in the summer and only charge to full when you actually need the range in the immediate future. Of course you'll need to periodically charge to full to balance the battery too.

Multiple partial cycles in the middle of the range are not more damaging than less frequent but deeper cycles so there's no problem keeping it between 40-60% and charging twice as often as running 30-70%.

There's no benefit to charging up to 80% unless you need the range. Damage will be greater at 80% than at 50% so just aim to keep it as close to 50% as you can be bothered. Likewise there's no point in running it down low before charging.

Charging and discharging slowly will put less strain on the battery so only rapid charge when you need the range to complete your journey, and avoid rapid charging to high states of charge if at all possible.

Also try to minimise rapid acceleration (although it's highly addictive).

Ultimately these are small wins against the tiny but insidious causes of long-term damage to the battery. It may amount to the difference between a 10% or 20% drop in capacity over 8 years.

Some people will obviously find it easier to just charge to full every day and not think about it. Especially if the car is leased or on PCP. But there's nothing wrong with making an informed choice about how to manage it.

And finally, don't let any of these factors reduce your utility from the car. Charge it as much as you need to so that you can use it as you want to.

This is complete nonsense.

Manufacturers have been very conservative with batteries (apart from Tesla, who are the exception). Real world degradation appears to be very low for most models.

If you want low degradation then Kia and Hyundai are the best. They give you the guaranteed usable capacity of the battery, not the raw capacity like other manufacturers. They have also shown very little degradation, cars with 100k miles still have a usable capacity of 64kWh which is what they were sold as. The actual batteries are thought to be around 69kWh so whatever degradation there has been came out of that buffer.

Grumpy_chap

It might be impossible to answer if people just have not reached this point but I'll ask anyway.

When a battery degrades on an EV, is it a steady rate of degradation or does the capacity of the battery suddenly fall off a cliff?

My comparison is a mobile phone.  For a long time, the battery is just fine, then after a while you notice that the battery is not lasting as long as it once did.  Once that point is reached, the rate of decline seems to be very rapid and it is not long until the shortened battery life is an inconvenience / annoyance of sufficient magnitude as to impact the usability and enjoyment of the phone.

Does a degrading EV battery also go to that curve of swift decline as to impact the use of the vehicle?

DrEskimo

Grumpy_chap said:

It might be impossible to answer if people just have not reached this point but I'll ask anyway.

When a battery degrades on an EV, is it a steady rate of degradation or does the capacity of the battery suddenly fall off a cliff?

My comparison is a mobile phone.  For a long time, the battery is just fine, then after a while you notice that the battery is not lasting as long as it once did.  Once that point is reached, the rate of decline seems to be very rapid and it is not long until the shortened battery life is an inconvenience / annoyance of sufficient magnitude as to impact the usability and enjoyment of the phone.

Does a degrading EV battery also go to that curve of swift decline as to impact the use of the vehicle?

Generally the opposite way around. There will be a more rapid decline in the early stages (typically it will read over 100% as it uses some of the 'buffer', then after a certain mileage it's quite a linear slow decline:



About the only things I would do is limit the amount I rapid charge (don't have that on the Zoe so not a concern), otherwise don't do anything in particular. The reported % is of the net capacity, not gross. So 100% probably is closer to 85-90% anyway. 

5yrs and 15k on my Zoe and I'm at 97% state of health....

Petriix

[Deleted User] said:

Petriix said:

Ignore the ignorant posts from people who tell you not to worry about it. There is a wealth of evidence that support your thoughts.

There are two main factors in battery degradation: time and use.

Calendar degradation is inevitable but can be minimised by keeping the battery as close to 50% state of charge as possible and keeping it as cool as possible. However, the colder it is (below the optimal 23 degrees C) the less efficient the battery will be at its primary purpose of storing and releasing energy.

Damage over time will be more significant the closer it is to the extreme ends of the voltage range. The BMS will protect it from the worst (but not all) of this.

It's fairly sensible to keep it parked in the shade in the summer and only charge to full when you actually need the range in the immediate future. Of course you'll need to periodically charge to full to balance the battery too.

Multiple partial cycles in the middle of the range are not more damaging than less frequent but deeper cycles so there's no problem keeping it between 40-60% and charging twice as often as running 30-70%.

There's no benefit to charging up to 80% unless you need the range. Damage will be greater at 80% than at 50% so just aim to keep it as close to 50% as you can be bothered. Likewise there's no point in running it down low before charging.

Charging and discharging slowly will put less strain on the battery so only rapid charge when you need the range to complete your journey, and avoid rapid charging to high states of charge if at all possible.

Also try to minimise rapid acceleration (although it's highly addictive).

Ultimately these are small wins against the tiny but insidious causes of long-term damage to the battery. It may amount to the difference between a 10% or 20% drop in capacity over 8 years.

Some people will obviously find it easier to just charge to full every day and not think about it. Especially if the car is leased or on PCP. But there's nothing wrong with making an informed choice about how to manage it.

And finally, don't let any of these factors reduce your utility from the car. Charge it as much as you need to so that you can use it as you want to.

This is complete nonsense.

Manufacturers have been very conservative with batteries (apart from Tesla, who are the exception). Real world degradation appears to be very low for most models.

If you want low degradation then Kia and Hyundai are the best. They give you the guaranteed usable capacity of the battery, not the raw capacity like other manufacturers. They have also shown very little degradation, cars with 100k miles still have a usable capacity of 64kWh which is what they were sold as. The actual batteries are thought to be around 69kWh so whatever degradation there has been came out of that buffer.

Physics and chemistry aren't the subject of opinion. It's simple fact. Whether or not the initial degradation is hidden by the BMS is a different matter. 'Very low' is a totally subjective term.

There simply aren't any 8 year old EVs with current battery chemistry. So you're speculating that degradation will be low enough not to bother you personally. All I'm saying is that there are simple ways to minimise potential degradation.

Given that these steps take zero effort, I'm not sure why you wouldn't follow them. Even if you can't be bothered personally, I'm even more baffled as to why you'd advise other people not to.

Flight3287462

How do you think these manufacturers keep the degradation figures low?

They have extra cells that are activated as the original dells degrade.  Lithium batteries degrade over time, no ifs or buts.

And if it appears they aren't there can can be only one reason.

Ectophile

Grumpy_chap said:

It might be impossible to answer if people just have not reached this point but I'll ask anyway.

When a battery degrades on an EV, is it a steady rate of degradation or does the capacity of the battery suddenly fall off a cliff?

My comparison is a mobile phone.  For a long time, the battery is just fine, then after a while you notice that the battery is not lasting as long as it once did.  Once that point is reached, the rate of decline seems to be very rapid and it is not long until the shortened battery life is an inconvenience / annoyance of sufficient magnitude as to impact the usability and enjoyment of the phone.

Does a degrading EV battery also go to that curve of swift decline as to impact the use of the vehicle?

Some of the earliest Nissan Leafs are now suffering from dead cells, which dramatically decreases the range.

But if you don't want the expense of a brand new pack, there are now independents who will dismantle the battery pack and swap out the dead cells with ones recovered from scrapped Leafs.

Other than that, nobody really knows yet how long the battery packs will last on other cars, because they haven't started failing yet.

Nebulous2

If I leave my leaf on a public charger overnight, is there a way to limit it to 80%? 

Other than getting up in the middle of the night and switching the charger off in the app.