Yet another (NMC) battery charging question/advice

[wenkatn]

Hello friends,

I have a trophy LR in UK. I work from home and only do short school runs on weekdays. Shopping and occassional day trips on weekends.
So basically 6 miles round trip school run on weekdays (30 miles) and shopping and trips on weekends anywhere between 20 and 200 miles. Weekly, i'm doing on an average 100-120 miles.

My charging plan:
Maintain SOC between 50 and 70% Mon to Thu. Typically top up 15% every couple of days to maintain it between 50 and 70%.
On Fri, a slightly bigger charge depending on the weekend plan taking it to 100% if a long trip planned or to 80% for shopping trips.
I charge to 100% at least once a month because of long trips by which I am also benefiting for the battery balancing.

I am quite happy with the routine. Do you think I should adapt a different strategy for my usecase?
I know it only makes very minimal difference, but would it be better to maintain it between 40 and 60% or 30 and 50% etc on the lower end of the SOC? Which would mean I will need to charge for longer on Friday-Saturday night for long trips to make it 100%. How about the speed of charging when charged from 30% to 50% compared to 50% to 70%. I believe the lower the SOC (not below 20%), the faster the charging speed. But anyways I pay for the kwh and not for the time. So not really into charging speed as i home charge on intelligent go at 7.5p/kwh and i only need 15% in the 6 hour window i got. So not a big deal. But would like to know if it would make any difference in battery health.

Why am i concerned?
I am planning to keep this car for 25+ years . Or as long as i could extend its life until the range is reasonable or the technology becomes obsolete.

Thanks,
Venkat

 

[Ian Key]

I wouldn't worry too much about battery health.
As long as it gets a balance charge on an AC charger every month, doesn't regularly sit at 100% for any length of time and isn't always charged on a fast DC charger, the battery will out live the car.

I think you could charge it to 80% Monday to Friday when the battery gets down to 40% then if you're doing a long trip at the weekend charge it to 100% the night before.

 

[MoDolph]

30%-50%, 40%-60% and 50%-70% are going to be very similar and very good for the battery health.

40%-60% looks to be a tiny bit better but not worth bothering about if it in any way makes your life harder. This study suggests ~3% difference between them in SOH after 750 cycles (150,000 miles at 200 miles per cycle)

 

[wenkatn]

I wouldn't worry too much about battery health.
As long as it gets a balance charge on an AC charger every month, doesn't regularly sit at 100% for any length of time and isn't always charged on a fast DC charger, the battery will out live the car.

I think you could charge it to 80% Monday to Friday when the battery gets down to 40% then if you're doing a long trip at the weekend charge it to 100% the night before.

Thank you. I might well do that. Instead of 15% every couple of days I could let it drop to 40% and charge up to 80% twice a week. I have untethered ohme epod charger and a 10m cable that i plug in every other day. Its a bit of work but got used to it.

30%-50%, 40%-60% and 50%-70% are going to be very similar and very good for the battery health.

40%-60% looks to be a tiny bit better but not worth bothering about if it in any way makes your life harder. This study suggests ~3% difference between them in SOH after 750 cycles (150,000 miles at 200 miles per cycle)

View attachment 21710

Thank you for the chart. Very helpful.

 

[Rolfe]

That was something I took from Euan McTurk on this video.



It's mostly about the NMC, with only the occasional throwaway line to the effect that with the LFP you don't need to worry about anything. He's a real expert, and he explains the chemistry of why the NMC battery tends to degrade at high SoC so that I actually understood it. I had previously had the wrong end of the stick entirely.

He is really reassuring even about the NMC, implying that you really don't have to be all that concerned about short-ish periods at 100% - he was talking not leaving the car there for weeks, rather than hours, and indeed "well, if you're going to SORN it, don't leave it at a high charge." Indeed, he even said that weeks wasn't a problem once in a while as long as you don't make a habit of it.

He also counselled against shallow cycles, doing short trips then always plugging in and going back to 100% so that the car was being constantly cycled up and down within the 80% to 100% region. But surely setting your maximum % charge to 80% and treating that as "full" will avoid that, and you can just do your 100% balance once a month and go back to the 80% routine after that.

 

[wenkatn]

That was something I took from Euan McTurk on this video.



It's mostly about the NMC, with only the occasional throwaway line to the effect that with the LFP you don't need to worry about anything. He's a real expert, and he explains the chemistry of why the NMC battery tends to degrade at high SoC so that I actually understood it. I had previously had the wrong end of the stick entirely.

He is really reassuring even about the NMC, implying that you really don't have to be all that concerned about short-ish periods at 100% - he was talking not leaving the car there for weeks, rather than hours, and indeed "well, if you're going to SORN it, don't leave it at a high charge."

He also counselled against shallow cycles, doing short trips then always plugging in and going back to 100% so that the car was being constantly cycled up and down within the 80% to 100% region. But surely setting your maximum % charge to 80% and treating that as "full" will avoid that, and you can just do your 100% balance once a month and go back to the 80% routine after that.

Thanks for the video link.

 

[OriginalBigAl]

I think for your usage you have got it spot on. There are a couple of youtube videos ( I cannot remember which) which are a little more technical with charts and excellent explanations that would concur with your findings.

 

[wenkatn]

I think for your usage you have got it spot on. There are a couple of youtube videos ( I cannot remember which) which are a little more technical with charts and excellent explanations that would concur with your findings.

Thank you. Yeah I watched a lot of them and settled on this pattern which works for me.

 

[stevegus]

The usual advice is to keep between 20-80%.

I would avoid multiple microcharges, plugging in every day. Thats unnecessary charge cycles.

I would be gobsmacked if anyone got 25 years out of a lithium battery in general daily use.

 

[wenkatn]

The usual advice is to keep between 20-80%.

I would avoid multiple microcharges, plugging in every day. Thats unnecessary charge cycles.

I would be gobsmacked if anyone got 25 years out of a lithium battery in general daily use.

Thanks. I had been topping up 15% every other day for my daily mileage needs. I’m sure that is not classified as a microcharge. Or I could top it up 30% every third day or so. I presume there won’t be any noticeable difference between these patterns.

 

[siteguru]

30% less often would be better than 15% more often. 45% even less often would be better still.

 

[Rolfe]

I think, if all of that is happening between 20% and 80%, we're well down the "don't worry about it" lane.

 

[Corindikev]

That is the best explanation of EV battery technology I have seen. Mainly because 1) the guy is an absolute expert and 2) he gets his message across in simple plain English that most people will be able to understand. It is a rare gift to be able to do this in an ad lib manner, keeping your audience captivated and explaining complex things in a simple way.

 

[Rolfe]

I was well impressed.