What's the effect on battery life of regularly charging to 100%

Our Tesla Model 3 SR+ over 3.5 years and 68k miles, lost 13% of its battery capacity, charged most days to 90% (approximately 70% AC charging, 30% rapid DC)
 
I don't now if there is a term for it but maybe it is "battery life anxiety" or "correct charging anxiety" but there are many people who just get in and drive their EVs without any concern about battery life, battery balancing, charging NMC to 80% or 100% etc.

At the everything Electric show in Australia, Rob Llewellyn interviewed a bloke who had just done 704,000 km in his 2018 Tesla model X & did heaps of Supercharging as well as home charging & didn't stick to any of the rules. At 666,666km the car said charging was going to be restricted or something & because it was still under warranty he got a brand new battery.

Worth a look. At the rate I drive it would take me 30 years to get to 600,000km. I just plug mine in when I am home & the sun is shining to get free power from my rooftop solar.

 
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tsedge said:
Charging to 100% is fine whenever you need it, it is recommended at least once a month to balance the battery.

The thing that ages a battery is time spent at 100% (or close to it), that's what you want to minimise - so don't leave it with a high state of charge. Rapid charging also has a wearing effect.

However, batteries last so well that it won't really affect you unless you plan to keep the car for 10 years and go well around the clock. All the models should be good for 200,000 miles with a decent battery life left.

Also make sure she has:
  • ECO mode on
  • Energy saving on in ECO mode
  • ECO set on AC
  • AC Temperature not too high and low fan speed
  • Intelligent battery heating set to OFF

145 miles should be no trouble at all for a LR, minimum I get even driving hard in sport mode is around 180 miles.

50mph should give you around 4m/kWh or more, suggesting that something is not set right.

Finally, there's nothing wrong with getting home with 12%.
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Good info, would this apply to a plug in hybrid? I have a PHIV TROPHY Hs Style?
 
Dr Euan McTurk (the go-to consultant EV battery chemist) has an excellent YouTube video on the subject. The one-line summary is that it's not the 100% which does damage; it's going to 100% on a rapid charger, which can cause the battery to overheat. Charging to 100% every day using a granny charger or home charger will do no lasting damage.

 
M44LCY said:
Dr Euan McTurk (the go-to consultant EV battery chemist) has an excellent YouTube video on the subject. The one-line summary is that it's not the 100% which does damage; it's going to 100% on a rapid charger, which can cause the battery to overheat. Charging to 100% every day using a granny charger or home charger will do no lasting damage.

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That's quite an old video, and doesn't mention LFP batteries at all. But more important, you've misunderstood it. He's not saying that going to 100% on a DC charger is going to damage the battery, he's saying it's a WASTE OF EVERYBODY'S TIME and needs to stop.

As always, he's saying that it's not the going to 100% on an NMC battery that might damage it, it's leaving it sitting at 100% or near that for a significant period of time, and especially constantly cycling it between 80% and 100%.

If I didn't post it earlier in the thread, here is a newer video where Euan explains it rather better I think, and also includes some information about LFP batteries.

 
Rolfe said:
That's quite an old video, and doesn't mention LFP batteries at all. But more important, you've misunderstood it. He's not saying that going to 100% on a DC charger is going to damage the battery, he's saying it's a WASTE OF EVERYBODY'S TIME and needs to stop.

As always, he's saying that it's not the going to 100% on an NMC battery that might damage it, it's leaving it sitting at 100% or near that for a significant period of time, and especially constantly cycling it between 80% and 100%.

If I didn't post it earlier in the thread, here is a newer video where Euan explains it rather better I think, and also includes some information about LFP batteries.

Click to expand...

It is old, but LFP is pretty recent and the video is still relevant for most EVs. I haven't seen this newer video and will look at it with interest. He did a long interview on the Everything Electric / Fully Charged podcast recently.

I'm pretty sure he did say (at some point, somewhere - yes, that's very vague and I would prefer to provide a reference) that charging near to 100% can cause the battery cells to overheat, but I won't argue the point. And yes, of course the main theme of the older video was the disproportionate time taken to charge the final KWhs. Plus the technicalities of equalisation.

In my defence, I was addressing the original question - What's the effect on battery life of regularly charging to 100%. I still say Euan's view is that regular slow charging does no significant damage and is therefore the better option. Myself, I tend to rapid charge only after a long trip - more for the convenience of refilling from a low SOC than anything. Maybe 4 or 5 times since getting my first EV last summer.
 
What he actually said was that the decline in charging speed as the battery gets close to 100% is to prevent it from overheating. I don't think there's any real harm in going to 100% on a rapid if you're not in a hurry and there's nobody waiting. I've seen videos of people sitting on a rapid all night at a hotel when it's all there was, and there were plenty chargers.

It's certainly received wisdom that AC charging is better for the battery, but in recent years more and more people are observing that even cars charged almost exclusively on DC are holding up extremely well.
 
pollenface said:
My friends in the off-grid community with LFP batteries seem to think LFP should not be kept at a high SOC.
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I think that may be because in an off-grid home energy system, you typically have the ability to charge the battery all day. When you charge LFP to full, they are at something near 3.5 or 3.6 Volts Per Cell, and keeping them at this high voltage is not a good idea. But with an EV, after balancing, you don't keep on charging, you disconnect completely. The cells then relax to a more moderate ≈3.4 VPC. They can stay that voltage indefinitely without fear of degradation.

So with a home energy system, there are constant loads and solar available during the day, so once the battery is full, you have to pick a voltage to aim for to keep the battery nearly full despite the day time loads. This they typically call a "float voltage", even though the concept is a little different to that of lead acid batteries that the float stage was designed for. Lead acid has enough self discharge even with no load that you need to overcome this self-discharge; LFP has much less self discharge, at least over the course of a day.

The necessity for this float stage might be why the off-grid people (myself included initially) feel that it's important not to keep LFP at too high of an SoC. Really, you don't want to keep the cells at too high a voltage, but the cells do that by themselves as long as you stop charging completely, as is the case with an EV.
 
I think there is a lot of confusion between the differences with LFP and NMC.

NMC won't let you charge to 100% on DC. It stops at anything between 94-97% depending on how the car/battery is feeling.

Does LFP go all the way to 100% on a DC charge?
 
I got pretty high on the Instavolt at Greenlands Farm Shop last summer, because the service in the restaurant was diabolically slow. I saw a post somewhere where I said it had gone to 99%, but I don't have a clear memory of that now. I made 97% on the village charger at home once, because I was in church at the time. But both times I really can't say whether it would have gone higher if I'd left it a bit longer, because it's so diabolically slow at that stage. I can't remember looking to see if either charger thought it was still charging the car, or if they'd stopped.
 
Coulomb said:
I think that may be because in an off-grid home energy system, you typically have the ability to charge the battery all day. When you charge LFP to full, they are at something near 3.5 or 3.6 Volts Per Cell, and keeping them at this high voltage is not a good idea. But with an EV, after balancing, you don't keep on charging, you disconnect completely. The cells then relax to a more moderate ≈3.4 VPC. They can stay that voltage indefinitely without fear of degradation.

So with a home energy system, there are constant loads and solar available during the day, so once the battery is full, you have to pick a voltage to aim for to keep the battery nearly full despite the day time loads. This they typically call a "float voltage", even though the concept is a little different to that of lead acid batteries that the float stage was designed for. Lead acid has enough self discharge even with no load that you need to overcome this self-discharge; LFP has much less self discharge, at least over the course of a day.

The necessity for this float stage might be why the off-grid people (myself included initially) feel that it's important not to keep LFP at too high of an SoC. Really, you don't want to keep the cells at too high a voltage, but the cells do that by themselves as long as you stop charging completely, as is the case with an EV.
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That's some pretty clear insight, cheers

I have a small off-grid project in my workshop, but I'm using AGM batteries
 

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