[John__S]

Hi All,

Thanks for reading this and my apologies if a similar question has been asked before.

I’ve never owned an electric car before but I’m looking at getting my first one and it’s a 2019 i3 with the 120Ah battery.

I followed YouTube videos which showed me Batta Kappa battery health estimate and it showed a figure of Batt.Kapa.max 36.4

But I don’t really have any idea of whether this number is good, bad or about normal for what you should expect on a 5 year old i3?

If anybody else has any advice it will be greatly appreciated!

Many thanks,

John

[RoryEssex]

Originally Posted by John__S

Hi All,

Thanks for reading this and my apologies if a similar question has been asked before.

I’ve never owned an electric car before but I’m looking at getting my first one and it’s a 2019 i3 with the 120Ah battery.

I followed YouTube videos which showed me Batta Kappa battery health estimate and it showed a figure of Batt.Kapa.max 36.4

But I don’t really have any idea of whether this number is good, bad or about normal for what you should expect on a 5 year old i3?

If anybody else has any advice it will be greatly appreciated!

Many thanks,

John

Hi John,

I’m a new owner (used i3) myself, so someone with more experience and knowledge may want to correct….but as I understand it the USABLE battery capacity from factory is 37.9kw. Also, Kappa figures should be used as an indication, not gospel.

I’m personally unsure if kappa relates to total capacity (42kw) or usable (37.4) , depending on which it is, 36.4kw would indicate 96% health against usable and 86.6% against total . Either way seems reasonable to me .

For comparison, my 2019 120Ah is reading 38.4kw after 87000 miles, however I know mine was charged it’s whole life on the reduced setting (16amp), rather than maximum (32amp), which is much kinder on the battery .

The Samsung batteries BMW used in the i3 seem to be pretty built proof, but if you can, always charge at reduced to extend the life.

Hope that helps and congrats on your new car, you’ll love it.

Rory

[John__S]

Hi Rory,

Many thanks for your reply which is much appreciated and really helpful!

That was good to find out that even if the battery health kappa test was run on a brand new i3 from the factory the test result wouldn’t have said 42.2kWH but would have read 37.9kWH at the time of being new.

It sounds like the battery health if your battery is fantastic at 38.4kWh at 5 years and 87,000 miles!

Even though the battery health of the car that I’m looking at buying is lower at 36.4kWh it sounds as if that’s within the realms of being reasonable for the age of the car and hopefully it’s certainly not a number to ring alarm bells or walk away from purchasing the car.

I’m very excited about my first ever electric car purchase and especially the i3 because I’ve read & watched reviews from happy owners and so hopefully I have a good experience as well.

Thank you so much for your help & advice!

John

[John__S]

Hi Rory,

Further to the above I also meant to say thank you for the advice about charging on a reduced setting.

Having not had an EV before I knew nothing about this.

Hopefully I’ll soon have a home charger and following your advice hopefully I can also select a setting to charge on a reduced setting to help protect the battery on my car going forwards.

Thanks again,

John

[RoryEssex]

Originally Posted by John__S

Hi Rory,

Many thanks for your reply which is much appreciated and really helpful!

That was good to find out that even if the battery health kappa test was run on a brand new i3 from the factory the test result wouldn’t have said 42.2kWH but would have read 37.9kWH at the time of being new.

It sounds like the battery health if your battery is fantastic at 38.4kWh at 5 years and 87,000 miles!

Even though the battery health of the car that I’m looking at buying is lower at 36.4kWh it sounds as if that’s within the realms of being reasonable for the age of the car and hopefully it’s certainly not a number to ring alarm bells or walk away from purchasing the car.

I’m very excited about my first ever electric car purchase and especially the i3 because I’ve read & watched reviews from happy owners and so hopefully I have a good experience as well.

Thank you so much for your help & advice!

John

It’s certainly not a number that should cause you any alarm , as mentioned before charging at the reduced rate (setting within iDrive) will extend the battery life, if you can, it does obvs increase the charging time .

Good luck with your purchase and like pretty much every other i3 owner, I’m sure you’ll love it, they’re great fun.

[RoryEssex]

Originally Posted by John__S

Hi Rory,

Further to the above I also meant to say thank you for the advice about charging on a reduced setting.

Having not had an EV before I knew nothing about this.

Hopefully I’ll soon have a home charger and following your advice hopefully I can also select a setting to charge on a reduced setting to help protect the battery on my car going forwards.

Thanks again,

John

No problem, general rule of thumb is the slower the charge the better for the battery. However, the occasional AC does do some sort of rebalancing within the battery, but the technical explanation on that is beyond my grasp ha

[RoryEssex]

Meant the occasional DC charge not AC

[John__S]

Originally Posted by RoryEssex

It’s certainly not a number that should cause you any alarm , as mentioned before charging at the reduced rate (setting within iDrive) will extend the battery life, if you can, it does obvs increase the charging time .

Good luck with your purchase and like pretty much every other i3 owner, I’m sure you’ll love it, they’re great fun.

Thanks for that info and I’ll be sure to look up how to select the reduced rate charging in the menu settings once I get the car.

Many thanks

[John__S]

Originally Posted by RoryEssex

No problem, general rule of thumb is the slower the charge the better for the battery. However, the occasional AC does do some sort of rebalancing within the battery, but the technical explanation on that is beyond my grasp ha

That’s helpful background about the reduced rate charging benefits and please don’t worry about not giving the really technical explanation as to why because I’m not the most tech minded and so it probably would have gone over my head.

Many thanks!

[Mondomensch]

It also helps the battery to only charge it up to 80 or maybe 90% rather than full, and try not to let it go below 15-20%. Basically, topping off or fully draining the battery causes more chemical/physical wear on the battery than the big middle range.

Also don’t get alarmed if the AC starts running during a (fast?) charge - that’s the battery temperature regulation system at work, and really helps to prevent early battery degradation.

[John__S]

Originally Posted by Mondomensch

It also helps the battery to only charge it up to 80 or maybe 90% rather than full, and try not to let it go below 15-20%. Basically, topping off or fully draining the battery causes more chemical/physical wear on the battery than the big middle range.

Also don’t get alarmed if the AC starts running during a (fast?) charge - that’s the battery temperature regulation system at work, and really helps to prevent early battery degradation.

Hi Mondomensch,

Thanks for your message!

And thanks for the tip about trying to charge when the battery is down to 20% and then to go up to 80%. My apologies if this is a stupid question but I’m completely new to EVs and the i3. So as I understand it the i3 doesn’t let you use the full 100% of the battery capacity (presumably to protect the battery) and you only have access to a ‘useable battery capacity’ as controlled by the car.

So if say roughly you charged the car to 100% would that be in reality actually only charging to say 80% because the useable capacity is already restricted. Or in order to protect & preserve the quality/health of the battery are you best to only ever charge to what the car says is 80% even if that’s just 80% of whatever the useable capacity is (so in actual fact less than 80% of the actual total battery capacity)?

My apologies if I’ve explained this really badly because I’m new to this and I’m trying to get my head around it all. Hopefully you can at at least get the idea of what I’m trying to say.

Many thanks,

John

[Mondomensch]

My understanding is that you’re right that charging to 100% indicated capacity still leaves a small "secret” extra capacity buffer in addition to that.

My impression is that that’s more like 10% of physical total, so I feel comfortable normally charging to 90% on the display. I also feel comfortable going up to 100% on the display occasionally.

The i3 battery system seems to be better engineered for robustness than that of a number of other brands, for example the Nissan Leaf.

[Mondomensch]

Just saw some info from user Gonville on the My BMW i3 forum site (also worth a look), indicating that one should periodically charge to 100% indicated:

it could be the pack is unbalanced which is why charging it to full indicated (which isn’t 100% actual) is a good idea to allow cell balancing. It does one cell each time the vehicle is charged. That has far more of an impact than does calendar age

What they are referring to is that each cell making up the battery is slightly different in its electrical characteristics and having one or more too different from the others can limit overall performance. Apparently charging to 100% lets the battery management software fully evaluate and compensate for one cell per charging session.

[John__S]

Originally Posted by Mondomensch

Just saw some info from user Gonville on the My BMW i3 forum site (also worth a look), indicating that one should periodically charge to 100% indicated:


What they are referring to is that each cell making up the battery is slightly different in its electrical characteristics and having one or more too different from the others can limit overall performance. Apparently charging to 100% lets the battery management software fully evaluate and compensate for one cell per charging session.

Hi Mondomensch,

Thanks for both of your posts above!

It's really useful to know that for battery health the battery shouldn't be charged to 100% on most charges but a charge to 100% every so often will do the battery good and so I'll try to work to that principle when I get the car.

Thanks again for your advice which is much appreciated!

John

[fogartym]

There is no evidence so suggest that you should not charge the i3 to 100% regularly. The advice I follow and others do as well is ABC - Always Be Charging.

Other vehicles may require only going to around 80% but not this one.

In any case, when you charge to 100% it is not really the case. There is a buffer top and bottom to protect the cells on this car from ever being charged to a true 100%.

My i3 2020 BEV has always been charged at home on a L2 charger and is plugged in most days.

It's SoH is currently 37.9KwH useable capacity against an official figure of a new car being 38.2 useable. My mileage is 109,000m.
The figure was part of a chargeable BMW health check.

These Samsung SDI battery packs are pretty much bullet-proof on 33KwH and 42Kwh models.

Never go from the 'Batt Kappa Max' reading - this is a guess-o-meter and should be treated as such.

TL;DR: It is an old-wives tale about charging the i3 to only 80%.