Charge to 80% or 100%?

[Thundarian]

I've read in several places over the last few years that charging an electric car over 80% is bad for the health of the battery, and should only be done rarely.

Since the Honda e doesn't have a very large battery capacity, this lowers the already low range down even further. For instance, if work is 40 miles away, with a motorway journey for most of the commute, all of a sudden, range anxiety might start to rear its head.

is this "only charge to 80%" still best practice? I think someone else said to not let it drop below 20%, and yet another person said not to charge about 60%! Now we've only got 40% of the battery at our disposal! This can't be right, can it?

[Trykpaa]

Honda put a reserve on the battery, and recommends to charge to 100%. We charge to 90% as I have the same considerations as you.

[bogga]

And charging to 90% is really charging to 81%, remember the battery is 35.5 kw, but only 28.5 usable, if the battery buffer is split evenly, 3.5 kw at the top and bottom.

[londiniumperson]

@Thundarian
No it's not right.

The manual states on p574:

To help extend the lifespan of the battery, it is recommended that you fully charge
the battery each time prior to driving

Also on p18 there is additional HV battery info.

I can guarantee that 99% of what you've heard/read is from uninformed/uneducated people who think that they know best because they read about it on line (probably from the cess pit called Facebook) or from a mate of mate who knows best.

Honda & other car manufacturers will have spent a lot time & money and their SQEPs know way more than the average person so I think that is best to read the manual and follow the documented advice.

[Reuben80]

Thundarian don't assume that the manual is right 100%.I never heard that charging to 100% keeps in good health the battery. Londiniumperson has every right to do so if he believes that but he has no right to say that I am uneducated.
Make research yourself, internet, youtube, battery professionals etc like I did to educate myself and decide yourself who do you believe.
I believe that the lowest SOC that you can afford to charge the better. It is up to you to decide.

There is a free app called Accubattery on google play store for your phone. You can see from that how it calculates the cycle of a battery if you are intersted you should try it.

[londiniumperson]

Thundarian don't assume that the manual is right 100%.I never heard that charging to 100% keeps in good health the battery. Londiniumperson has every right to do so if he believes that but he has no right to say that I am uneducated.
Make research yourself, internet, youtube, battery professionals etc like I did to educate myself and decide yourself who do you believe.
I believe that the lowest SOC that you can afford to charge the better. It is up to you to decide.

There is a free app called Accubattery on google play store for your phone. You can see from that how it calculates the cycle of a battery if you are intersted you should try it.

@Reuben80 My comment of 'uninformed/uneducated people' is specifically in the context of EV battery technology, there are lots of educated people but very few in this area and even fewer with extensive real world experience.

Car & battery manufacturers spend a lot of resources developing battery solutions and they need payback on this investment so the average person will never have access to these current trade secrets.

Using the internet to determine the truth about this subject is fraught with issues because so much of it is incorrect or outdated.

It seems that you've just contradicted yourself by saying not to believe a huge world wide company manufacturer's documentation but to believe a random person on the internet (yourself) who knows best because they've read things on the internet to the contrary.
You then quote a battery performance app (with in app purchases) on google play as a good example of a battery performance/life. Mobile phone & EV battery charging technology are not the same, at it's simplest an EV's BMS is significantly more advanced than a phone's.
I had a look and their tag line is

AccuBattery monitors and optimises battery health & performance via science!

That's a huge red flag to me meaning 'we don't have a clue but we can quote all sorts of links to stuff/bullshit on the internet'.
Then in their 'research and methodology' webpage they state:

We try to use primary sources (directly referring research papers) as there are lots of conflicting claims on how batteries work and most articles don't cite their sources.

then they go on to state that the sources they use

don't cite all their data source.

to then go on to make their own assumptions where the data is not available to them or the public.

[milligoon]

Difficult to know what is correct for each cell type and each configuration of each bank.

The fact that Honda have limited the car to around 80% would give the impression that they have taken away the need for the owners to concern themselves by having to approach the charging by spreadsheet.

What needs to be made clear is the battery warranty, is it x% of the whole battery or y% of the usable battery as 70% of the whole is 70% whereas 70% if 80% is only 56% of the whole battery, which figure applies incase of a warranty claim.

(sarcasm)
Mind you by then all these cheap magic high density batteries will be common place and will be peanuts to upgrade

(/sarcasm)

[londiniumperson]

Difficult to know what is correct for each cell type and each configuration of each bank.

The fact that Honda have limited the car to around 80% would give the impression that they have taken away the need for the owners to concern themselves by having to approach the charging by spreadsheet.

What needs to be made clear is the battery warranty, is it x% of the whole battery or y% of the usable battery as 70% of the whole is 70% whereas 70% if 80% is only 56% of the whole battery, which figure applies incase of a warranty claim.

(sarcasm)
Mind you by then all these cheap magic high density batteries will be common place and will be peanuts to upgrade

(/sarcasm)

All we know for sure is that Honda advertise:

EV Battery Capacity (kWh) 35.5

but only allow the owners to use about 80% of it.

[Jeffers]

If the battery capacity is guaranteed for 8 years to 70%, it should be guaranteed to 70% of 35.5kWh, as @londiniumperson suggests as it's the advertised capacity.

I honestly don't know what is best for the battery, but conventional wisdom of NCM battery chemistry is to keep is as close to 20-80% as possible from what I have read. I seem to remember a Warwick Uni study suggesting this but having trouble finding the source. Different chemistries of battery cell make up require different care, but the Honda seemingly has NCM 622 cells.

It's your own car so charge it how you like. Whatever you do will be within the parameters set by Honda, because you have no other choice. This is liable to change with OTA updates though, and may depend on individual data from the BMS.

[Reuben80]

Londiniumperson, it's OK if you don't believe what I say but you don't even believe what a big car maker like VW say about maintaining the batteries of the ID3?
Watch here, from minute 5. Extraction from the manual of the ID3