Charging best practice for battery longevity

mp3guy

What's the consensus on this these days? I've seen a lot of different recommendations online, varying from not worrying about charging to 100% because of extra capacity built in, to not leaving the car sit with more than 60% battery when not in use for an extended period of time.

I've seen a few places saying to avoid fast DC charging if possible and stick to home charging. Also something about letting the battery completely run down at least once a month before charging it back up.

Wondering about people's experiences here.

adunis

Just charge it however, whenever.

Lumen

Don't keep it at more than 90% or less than 10%.

This looks good.

What can 6,000 electric vehicles tell us about EV battery health?
Compare the average battery degradation for different vehicle makes and model years.
https://www.geotab.com/blog/ev-battery-health/

zg3409

They say age of battery matters more than charging style. Also it depends on you car and how the battery is managed. Example if you fast charge a leaf the battery gets hot while most other makes have a way of cooling the battery and so fast charging is less harmful for the battery. Some makes gave a hidden % reserved which you cannot use so you are never actually charging to 100% even when the car says 100%.

If you need to charge daily then you don't have much choice, many cars don't have an easy way to stop the charge at say 90%. In some cars they even took that option away in later models. Best not to keep charging the car unnecessarily to 100% 7 days a week, best not to leave it at a low state of charge for a long time (e.g. 10%). If parking it up for a few weeks try to park it will 40-80% for best battery life. Another side note is rarely charging your car is not good for the 12v battery as many EVs only top up 12v battery when driving or charging but not when sitting around not plugged in. This can mean your 12v will need replacing earlier, and you may end up needing a jump start if you drive rarely and charge rarely. But life it too short to really worry about such things, the manufacturers should try to keep the batteries in the happy zone as much as possible. The good news is bigger EV batteries will have less wear as they are rarely driven low every day like small EV batteries. The extra reserve means less overall use of the battery. I would avoid a leaf if you want a really long battery life.

The running the battery down once a month is mostly so your GOM (range guess) is accurate, as if you don't run the battery down the BMS guess of the range can become quite bad, and range may suddenly drop at low levels and give you a fright. Generally the BMS will try protect the battery at very low and high levels and when hit or cold and so it will stop the car from driving or slow charging speed to protect the battery from damage. They also recommend not stopping charge at say 90% every day and to fill to 100% once a month.

Gumbo

I plug in every day.
Charge to 100% every day.

alanowx

Here is another interesting article, this one by Pedro over at Pushevs called - Battery charging: Full versus Partial.

https://pushevs.com/2018/04/27/battery-charging-full-versus-partial/

This is a sample chart
Quote "

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Summing up, if you really want to take care of your battery try to limit charging to 70-80 % of its capacity, even if it means that sometimes you’ll need to discharge it almost till empty. Of course this is only advisable if you already know your electric car’s range limits and don’t suffer from range anxiety"

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End of Quote.

As an a non BEV owner without practical or technical knowledge on the subject, taking this chart in particular at face value, - somewhere between 10 - 70 may seems ideal , taking 60% on board, apparently better than 20 - 80% possibly gaining 2,500 extra cycles. (3,500 vs 5,500)

Then again what do I know - but a good read none the less, incl comments at bottom.

alanowx

alanowx wrote: »

As an a non BEV owner without practical or technical knowledge on the subject, taking this chart in particular at face value, - somewhere between 10 - 70 may seems ideal , taking 60% on board, apparently better than 20 - 80% possibly gaining 2,500 extra cycles. (3,500 vs 5,500)

Then again what do I know - but a good read none the less, incl comments at bottom.

As I said what do I know, - I can't even subtract

unkel

alanowx wrote: »

Summing up, if you really want to take care of your battery try to limit charging to 70-80 % of its capacity

Not this nonsense again.

alanowx wrote: »

sometimes you’ll need to discharge it almost till empty.

And more nonsense.

As adunis said, just charge the car when you need to. It's fine. There is a warranty of 8 years on the battery and if the battery is at 80% capacity (fast charge the hell out of it to full all the time) or 90% capacity (baby it, only ever charge it to 80% and never below 20%) makes no material difference to the value of the car when it is 10 years old.

alanowx

Unkel - Not my words, just quoting from the article, but I believe Pedro is well respected in EV community.

Realistically I'd say bye the time one got to 5-6,000 charges you may well have bigger concerns with the car than the state of the battery.

From all those comments in that article, most of which way over my head, the one that made most sense to me was as simple as charge only to as much as you need.

Water John

Remember you need to fully charge occasionally to allow for cell balancing.

liamog

Whilst Pedro's analysis is likely well sourced, its largely dealing with cycle life of cells.

With the original Ioniq the available capacity when new is already 90% of the actual capacity of the available energy. Most of that buffer is on the top end of the battery. So let's simplify and say it matches to 90% to 0% range or approx 1,500 cycles.

That means the battery life has a rated life of approx 1,500 x 28kWh = 42,000kWh, my experienced efficiency is approx 15.6kWh/100km giving it a rated life of about 270,000 km before the battery degrades enough to warrant a replacement. I could set my car to only charge to 90% (which is actually 80%) to double the km to 540,000 but it barely seems worth the effort.

Lumen

Water John wrote: »

Remember you need to fully charge occasionally to allow for cell balancing.

In which cars? AFAIK Teslas rebalance cells at various states of charge and don't benefit from this.

unkel

If you really want to make the most out of your lithium battery, only ever cycle it between 25% and 75% and always keep the temperature at a constant 21C. The battery will still work when our grandchildren are all dead.

liamog wrote: »

I could set my car to only charge to 90% (which is actually 80%) to double the km to 540,000 but it barely seems worth the effort.

That's exactly what I mean. It makes no material difference to the value of the car after 10 years whether the capacity at that stage is 80% or 90%

It's been well documented and I've been saying it for years that the less of the battery you use the more cycles you get from it. If you need to use all of it then use it.

It's proven and there are many papers peer reviewed on the subject, it's not like climate change where we still have to wait 100+ years to see if the predictions of Climate models come true, battery research has been physically verified.

Smaller batteries will be cycled much more and some are more resilient than others and it won't matter, cycle life is also improving and Kwh is getting more and more so it won't be as much of an issue because a 30% loss in a 24 Kwh - 40 Kwh battery is a much greater deal compared to a 30% loss in a 60+ Kwh battery.

Some car manufacturers like Nissan choose not to control their batteries temperature and this has shown to probably have much more of an effect to battery degradation even in Ireland if driven hard and fast charging a lot, reducing battery current when charging due to a hot battery is laughable.

Now as I said, if you got 60+ Kwh I wouldn't worry too much because the car will rarely see a full cycle and the calendar life will take over as being the greatest cause of degradation, I still wouldn't leave the car charged to 100% all day every day or over 80% all day every day because the higher the charge the more stresses it causes the battery over time.