EV battery management

ComicGeek

I'm awaiting delivery of my first EV, and looking to understand how to maximise battery life - I'm not so concerned about day-to-day range as I have easy access to chargers, it's more about prolonging the maximum range as the battery ages. It's not on lease/PCP, and I won't be changing the car for at least 8 years.

Skoda provide a battery energy content degradation warranty for 8 years/100,000 miles, that covers an energy content reduction of more than 30%. Given other studies into battery degradation, I would hope that I could achieve a lower reduction than this, but want to put certain measures in place from day 1 with a brand new battery to help. I can't see any additional instructions in the warranty document or owners manual, so I assume the 30% reduction is based more on faulty cells than poor battery management by the owner.

So what I've been told already is:

1) Keep the battery charged between 20%-80%, and really limit going below or above these. Limiting lower and upper battery levels is easy, as I can set that through the car and chargers - I'm also not doing high daily mileage, more 40-50 miles consistently each day. But should I run it down to 20% each time, or charge it back up to 80% after each use? 

2) Don't keep the car sat for long periods at empty or full - 25%-75% if away for a long holiday, or infrequent use.

3) Don't plug in as soon as you get to the charger - allow the battery to cool down before plugging in. But I assume this is more if you are doing lots of motorway driving and using the battery harder, rather than a short hop to the shop?

4) Limit use of rapid chargers, and particularly use slow chargers when it's cold.

Apart from point 1, am I also over thinking it? As an engineer I'm always looking for that perfect answer, but mindful of spending a lot of time for limited gain!

BOWFER

I'm on my second EV, I've literally spent years on EV forums etc.
Ignore all of the above, just charge it how you blooming well like and enjoy it. 

MX5huggy

Just charge it and drive it, it has a battery management system to look after the battery, it’s not a 2005 Nokia mobile phone. In particular it will need charging to 100% (not actually 100% because it has a buffer that BMS saves) so it can carry out balancing charges where it equalises all the cells to the same voltage. 

[Deleted User]

Ideally keep it between 30% and 70% if you are not needing more range. You can run it down to 30% no problem.

Also do an occasional 100% charge as this allows the battery cells to balance. Maybe once every month or two, or if you notice that the range estimate/battery % seems off.

As for letting the battery cool down when you are going to charge, that's nonsense. The battery doesn't like being charged in extreme cold or extreme heat, but the car has a battery management system that takes care of that by heating or cooling it, and by limiting the charge power. For AC charging it's so slow that it doesn't matter, for DC charging you may very occasionally find that you don't get maximum speed but you can just let the car worry about it.

Petriix

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.

BOWFER

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's also evidence against all the faffing around, like taxi firms with Leafs that have been rapid charged every day of their life for years and still great battery health at +150K miles etc.
The OP has unwittingly opened one of the biggest cans of worms in EV motoring.
I know I'm not worrying about it but, as you say, I'm one of those that will only have the car for a relatively small number of years and I couldn't give a stuff what the battery will be like in 2031.

Keep_pedalling

You don’t need to charge to 100% unless you have a long trip coming up. I limit mine to 80% but don’t worry too much about the lower end, just top up to 80 a couple of times a week from a starting point of 20-60%.

ComicGeek

The range is around 330 miles, so I'll only be using about 10-15% of this per day. Very rarely will I need more than 50% of the range.

I'm happy to recharge this 10% each day if it really extends the battery life. I'm planning to keep it at least 8 years, so happy to do whatever is needed to maintain the battery - to me, working to maintain even 10% of the battery range is worth doing.

Thanks for all the comments. There's lots of 'guides' on this by journalists, but nothing from the car manufacturers themselves. The best I found was on Kia's website, but hard to get a complete answer on it.

Petriix

BOWFER 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's also evidence against all the faffing around, like taxi firms with Leafs that have been rapid charged every day of their life for years and still great battery health at +150K miles etc.
The OP has unwittingly opened one of the biggest cans of worms in EV motoring.
I know I'm not worrying about it but, as you say, I'm one of those that will only have the car for a relatively small number of years and I couldn't give a stuff what the battery will be like in 2031.

Having actually driven a Leaf as a taxi, I can categorically say that daily rapid charging absolutely ****s the battery. The Leaf is especially vulnerable to this because it lacks any active thermal management.

Bigwheels1111

My mate has an MG ZS Exclusive.
He has only charged it twice on fast chargers. It has liquid cooling for the battery which helps.
Its done 2000 miles so far on £40 or less of charging. He uses Tesco, Sainsburys etc free 7kw chargers.
Once a month he plugs in at home for a balance charge over night. 5 months in and still says 211 miles on eco when fully charged. Same as day one when he picked it up. Car is 10 months old and not lost any range.

Petriix

Bigwheels1111 said:

My mate has an MG ZS Exclusive.
He has only charged it twice on fast chargers. It has liquid cooling for the battery which helps.
Its done 2000 miles so far on £40 or less of charging. He uses Tesco, Sainsburys etc free 7kw chargers.
Once a month he plugs in at home for a balance charge over night. 5 months in and still says 211 miles on eco when fully charged. Same as day one when he picked it up. Car is 10 months old and not lost any range.

That's a lovely story. The 211 miles is what we call the GOM (guess'o'meter) because it's just a made up number. The ZS isn't actually capable of that kind of range (maybe they have an MG5?).

The only way of actually measuring the battery capacity is to empty it completely and measure the energy used to fully recharge it. While it's certain that the battery will have suffered from *some* degradation, this could easily be entirely hidden by the BMS.

I've certainly not seen any noticeable drop in range in my 10 month old MG5, but I do take extra steps to protect the battery.