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In reality, you probably won't have it long enough to notice the effects, assuming you swap cars every 2-3 years like the majority of folk.
 

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Batteries degrade over time regardless of use. There is a wealth of data indicating the ideal conditions to minimise this degradation. Manufacturers aren't going to give people technical tutorials on the intricacies of this; they will just tell people to avoid the extremes and trust the BMS to do a reasonable job. It's a ludicrous stretch of the imagination to suggest that the BMS will prevent all avoidable degradation.

The BMS is what stops your car battery from becoming completely unusable in 5 years in the way a laptop battery does. The advice to take sensible steps to look after the battery are what reduces degradation from 3% per year to 2%.
 

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The HV pack will have a small upper and lower buffer to help protect the pack.
There is a lot of opinions on what level the battery should be charged up to and left unused.
MG recommends that you should charge to 100% every time, in order to balance the pack.
I guess this is fine if the car is in constant daily use and used after receiving that full charge.
But under the current situation, I personally feel that charging to 100% and then leaving the car just sitting on the drive for a long period, is not the way to go.
Why bother risking any long term harm to the HV pack, by fully charging and then just having it sit there, it makes no sense to me.
If your car is on lease or PCP then the long term affects of this process is not likely to be felt by the current owner.
Our present usage has ( like everybody else ) reduced to drastically.
One weekly trip to the local supermarket of about 15 miles and we are done.
So, why charge the car to 100% for a this trip only ?.
I still support the idea that keeping the pack between 20 - 80% of its capacity is a better option.
It has taken me almost three weeks to reduce the predicted mileage down to 70 miles on the GOM now.
So imagine if I had charged the car to 100% then it would have been at this high SOC for almost three weeks now !.
I have no issue charging to 100% if I intend to use the car.
We have managed to cover 8500 miles this year and encountered two lock downs.
I therefore charge to a level that meets my requirements.
Currently, that is very very small.
I luck forward to fully charging and getting out to enjoy my EV once again I hope !.
Take care folks !.
 

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If you leave it too long without charging (or taking it for a run) then your 12 volt battery will go flat. Also, don’t forget that the BMS retains battery capacity and doesn’t charge to 100% nor does it allow complete discharge.
For all intents and purposes I would suggest ignoring the Battery University advice and follow the manufacturer‘s advice unless you plan to keep the vehicle for 150,000 miles plus. One day you will be half charged and need to do an extended run at short notice and have to wait a few hours to charge it up!
My car has been left for more than 5 weeks without charging or being used as the 12v battery was still fine.
 

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Do they define what they mean by "long-term"? There's a massive difference between a few weeks on a driveway vs a few years on a shelf in a warehouse.
It does depend on electrode composition and electrolyte chemistry. If you are interested there is a peer reviewed article here:


In the results and discussion, this is quite interesting. "Cells stored in a discharged state below 20% SoC exhibit the least capacity fade. Storage levels between 20% and 50% SoC cause a medium degradation rate. The fastest capacity fade occurs at a SoC interval between 60% and 90%. A fully charged cell, however, shows a somewhat slower capacity fade again."

So from that experiment, it found that keeping the battery at or below 60% gave the lowest rate of degradation. In reality, the car would probably have fallen apart from age before serious degradation would be an issue. :)
 

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Discussion Starter #26
OK, so I idid a run today with heat full blast and got it down to 93%

In reality, you probably won't have it long enough to notice the effects, assuming you swap cars every 2-3 years like the majority of folk.
Seriously? Nobody I know buys a new car every 2 - 3 years. Way to suffer most from depreciation.
 

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The fastest capacity fade occurs at a SoC interval between 60% and 90%.
That's a very interesting finding, as it somewhat defecates all over the "only charge to 80%" mantra that I see quite a lot.

I'm taking the approach of assuming that VW have designed the car well enough that I won't need to use their battery warranty, and I'll probably flog the car before the battery warranty expires anyway. But it's probably much easier to be relaxed about it in a PHEV, because I really just need the battery to be good enough to start the engine for the car to still be functional (albeit not economical).
 

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you might loose a few miles off your maximum range a few years down the line, but in truth if its only for a few days you are unlikely to notice anything.

Ideally you should take it around the block with the AC and heating on high, but I wouldnt loose any sleep over it.
 

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That's a very interesting finding, as it somewhat defecates all over the "only charge to 80%" mantra that I see quite a lot.

I'm taking the approach of assuming that VW have designed the car well enough that I won't need to use their battery warranty, and I'll probably flog the car before the battery warranty expires anyway. But it's probably much easier to be relaxed about it in a PHEV, because I really just need the battery to be good enough to start the engine for the car to still be functional (albeit not economical).
only charging to 80% made such a large difference to Leaf to battery longevity that Nissan removed the limiter ability to only charge to 80% from later models...
 

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In the scheme of things not something to loose sleep over.
A lot of us sitting at home today then with nowhere to go, rarely are do many replies posted in so short a time.
There are also sound economic reasons not to charge to a high level this week if you are on Octopus Agile, todays rates are pretty high. I am waiting for a windy day for some cheaper electricity. The car can sit at 30% till that happens, going nowhere.
 

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I assume that there is a built-in protection that you cannot charge too much (90%) or too little (10%), I know if my car indicates 0% battery that it is therefore not empty ...
Sure, but you don't have that much buffers. More like 100% is really 96% or thereabouts.

The temperature is also a factor for aging, so now is not the worst time to let the car sit with a high SoC.

I would take it for a spin like twice, or at least once, a week or so to get some maintenance charging of the 12V battery and wear the rust off of the brakes.

Sent from my ONEPLUS A5000 using Tapatalk
 

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OK, so I idid a run today with heat full blast and got it down to 93%



Seriously? Nobody I know buys a new car every 2 - 3 years. Way to suffer most from depreciation.
Nobody under a certain age buys cars. PCP/lease, 2 or 3 years, swap it at the end. Monthly payments are a sunk cost of having access to a reliable vehicle.

Heck I’ve had 3 new cars this year alone. 5 cars in total over the last 24 months, plus another 3 or 4 rentals and a cancelled order. But my requirements change more often than I’d like.
 

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only charging to 80% made such a large difference to Leaf to battery longevity that Nissan removed the limiter ability to only charge to 80% from later models...
As I understand it, the reason for removing the 80% limiter option was not because it wasn't needed, but that removing it increased the EPA range (due to the way EPA is calculated)...


"The official EPA range for the 2014 and 2015 model year Leaf, increased from 121 to 135 km (75 to 84 miles). The difference in range is due to a technicality, as Nissan decided to eliminate the EPA blended range rating, which was an average of the 80% charge range and the 100% charge range. For the 2014 model year, only the 100% charge range figure applies."
 

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Considering the Kona battery only has a 5% buffer, it is anywhere between 95% and 100%, probably 97%. So you think it is OK to have Li-Ion sitting at 95% or 97% for prolonged periods?
5% buffer based on capacity, or voltage. What are you basing your assertion that the car is sitting at 97% on (a fictional B U battery).Come on this is pub talk!
 

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5% buffer based on capacity, or voltage. What are you basing your assertion that the car is sitting at 97% on (a fictional B U battery).Come on this is pub talk!
Also, in this banter, is anyone factoring the effect of temperature?

A week at 40 degrees C must be the same as what a year at 5 degrees C???? 😁😁😁
 

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Also, in this banter, is anyone factoring the effect of temperature?

A week at 40 degrees C must be the same as what a year at 5 degrees C???? 😁😁😁
This paper tests SoC against temperature for calendar degredation (baseline) versus regenerative braking degredation. It's an interesting read and answers your question.

https://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwiBgarbmZnuAhUaQUEAHZ39Di8QFjAGegQIDBAC&url=https://www.mdpi.com/2032-6653/7/1/41/pdf&usg=AOvVaw3l1aHxU_nwfYaygz8u8UOK

To summarize:

"4.5 Optimal Operating Conditions Our study shows that cyclic aging increases with lower temperature and calendar aging increases with higher temperature. Thus, an optimization is necessary to minimize the aging of a Li-ion battery. During storage periods, temperature should be kept low to reduce calendar aging. When cycling the battery, especially when charging the battery, a higher temperature should be established to minimize aging due to lithium plating. When charging the battery for a longer time at low temperature, current rates should be kept low to reduce lithium plating."
 

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This paper tests SoC against temperature for calendar degredation (baseline) versus regenerative braking degredation. It's an interesting read and answers your question.

https://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwiBgarbmZnuAhUaQUEAHZ39Di8QFjAGegQIDBAC&url=https://www.mdpi.com/2032-6653/7/1/41/pdf&usg=AOvVaw3l1aHxU_nwfYaygz8u8UOK

To summarize:

"4.5 Optimal Operating Conditions Our study shows that cyclic aging increases with lower temperature and calendar aging increases with higher temperature. Thus, an optimization is necessary to minimize the aging of a Li-ion battery. During storage periods, temperature should be kept low to reduce calendar aging. When cycling the battery, especially when charging the battery, a higher temperature should be established to minimize aging due to lithium plating. When charging the battery for a longer time at low temperature, current rates should be kept low to reduce lithium plating."
So was I correct, ie a few days at 5 drgs C is the same as a year at 40 ?
 

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It does depend on electrode composition and electrolyte chemistry. If you are interested there is a peer reviewed article here:


In the results and discussion, this is quite interesting. "Cells stored in a discharged state below 20% SoC exhibit the least capacity fade. Storage levels between 20% and 50% SoC cause a medium degradation rate. The fastest capacity fade occurs at a SoC interval between 60% and 90%. A fully charged cell, however, shows a somewhat slower capacity fade again."

So from that experiment, it found that keeping the battery at or below 60% gave the lowest rate of degradation. In reality, the car would probably have fallen apart from age before serious degradation would be an issue. :)
I'd like to see at least one other independent study which corroborates the finding in this paper that age related degradation is slightly less at 100% charge than 80%. Can anyone find any unrelated research drawing the same conclusion ? Otherwise it could be a case of picking one piece of evidence that happens to agree with a certain view point.

I've read quite a few battery research papers and also manufacturers cell datasheets over the last few years of EV ownership and this is literally the first one I've seen that came to this conclusion. Also, you have to wonder why a company like Tesla would make 80% charge the default and strongly recommend only to charge to 100% for long trips if it was actually less harmful to charge to 100%.

Because no other research that I've seen agrees with the claim in this paper I have to consider the possibility that there is an error in their methodology.
 
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