[MichaelJohn]

I have a 2015 i8 with the original 12 V battery and I want to make it last as long as possible. Since battery access is problematic, a battery tender is not practical. I think I heard on Pat‘s Garage Online that keeping the car plugged in trickle charges the 12 V. I have been leaving the car plugged in, but I’m wondering if I’m doing it any good, or harm?

Opinions?

[MolarBear]

I can't answer your points, but on a separate note, I'd probably factor in a 12v replacement soon at 6 years old, so I wouldn't sweat too much about it.

[Mr Squarekins]

Mines always plugged in. So far it's been fine - 2 yrs.

I believe it charges the 12v battery.

[F5506m]

Mine is always plugged in at night when at home. Second i8 and no issues.

[thinkingindigital]

2015 here as well. My original battery doesn't charge past 17 mi so I'm likely in need of a replacement. I can't speak to when it degraded as I only recently look possession. But in any case, I leave it plugged in all night.

[F5506m]

Originally Posted by thinkingindigital

2015 here as well. My original battery doesn't charge past 17 mi so I'm likely in need of a replacement. I can't speak to when it degraded as I only recently look possession. But in any case, I leave it plugged in all night.

17 miles is pretty good for a Pre-LCI car. My old car was a 2016 and i would be lucky to get over 16 miles.

[thinkingindigital]

Originally Posted by F5506m

17 miles is pretty good for a Pre-LCI car. My old car was a 2016 and i would be lucky to get over 16 miles.

Good to know. Are there service upgrades for this or do I just live with it? It doesn't really bother me - it's a part time driver around town for me. But if an option exists to improve the battery, I'd be interested.

[F5506m]

Originally Posted by thinkingindigital

Good to know. Are there service upgrades for this or do I just live with it? It doesn't really bother me - it's a part time driver around town for me. But if an option exists to improve the battery, I'd be interested.

There is no service that will increase the range as your car has a battery capacity of 7.1 kwh being a pre-LCI cars. The 2019-2020 cars had a larger battery (11.6 kwh) that increases range to 22-25 miles.

I do not know anyone who has upgraded the older batteries. I am sure it can be done, but maybe be cheaper to just upgrade to the newer car.

[ChiTownM]

I have an early build …. 2014 and I always plug it in, especially during winter when it is stored. All systems and batteries ok. Today it is 72 degrees and the app indicates 17 miles fully charged.

I am really disappointed that the app won't work anymore once the car will lose 3G network connectivity. And I am not certain the 2014 will work with the display key. Sucks to be an early adopter.

[Coastali8]

I have a 2015 that is a occasional use weekend car. It’s always plugged in.
The 12v battery is maintained on charge from the traction battery when the car is plugged in.

The car has been plugged in consistently since new when it’s not being driven. The 20Ah, 7.1 kWh, 355v traction battery BMW says must have 5.2 kWh useable at full charge to be considered 100%.
My battery reports 5.4 kWh still after 6 years and delivers the normal 16-18 miles expected range.

I’m still on the original 12v battery. I’m thinking about changing it out soon just for a little preventative maintenance. I just hate the idea of having to buy a battery from the dealership and paying for installation and registration. A 12v battery should be something the car owner can replace without a visit to the BMW dealer.

I have the OBD interface and necessary app to register a new battery but I can’t purchase a proper replacement battery anyplace except from BMW. The closest match I can find is the Remy FT560 group 26R. I’m tempted to give it a try.

[MichaelJohn]

Originally Posted by Coastali8

I’m still on the original 12v battery. I’m thinking about changing it out soon just for a little preventative maintenance. I just hate the idea of having to buy a battery from the dealership and paying for installation and registration. A 12v battery should be something the car owner can replace without a visit to the BMW dealer.

That’s the part that really annoys me. I have called a couple of dealerships and been quoted $700+ from each for a new 12v battery. They’ve got us with the damn coding issue, though you seem to have that figured out. I have a friend that suggested calling TripleA and having them change the battery while the car is running to avoid having to code it. Then BMW told me that the car wouldn’t know it’s a new battery and there could be issues with that because the car somehow compensates for an aging battery. Don’t know if that’s true, but it adds doubts to doing it myself. I have always changed my own batteries and I don’t like getting gouged for such a simple service.

[Coastali8]

My understanding is that is true about the car adjusting the charging system for the new 12v battery.
I’m afraid we will just have to suck it up and spend $700 for a damn battery.

[Philk]

Originally Posted by Coastali8

BMW says must have 5.2 kWh useable at full charge to be considered 100%.
My battery reports 5.4 kWh still after 6 years and delivers the normal 16-18 miles expected range..

I've just purchase a 2016 car from a main dealer and had 16 miles showing after a full charge. When you say your battery reports 5.4 KWh, how do you find that out? Since my car now has a full year of warranty which includes the main battery, what level would it need to drop to for BMW to consider changing it (assuming they would do so under warranty)

[Coastali8]

To find your traction battery capacity just add the total of the last 5 digits of your VIN number together.
Press your trip meter reset button and hold for 10 seconds.
A menu will appear, select unlock and hold for 3 seconds. Enter the VIN total by repeatedly pressing the button.
Select from the menu TANK. Read “batt Kappa max.”
Press and hold to exit.
5.2 kWh is max usability for a pre LCI car traction battery. Your number could be a little higher if your battery is in good condition.

I can’t remember what level the “Kappa max” would have to decrease to for BMW to replace your battery as being defective. It’s somewhere in one of these threads as is the above procedure but I think it’s a lot. I believe 15-18 miles is about the standard range for a fully charged pre LCI battery, but that number is calculated based on how you have previously driven the car.

I leave my car plugged in all the time when it’s not being driven. Nearly 7 years now. No issues. The 12v battery is trickle charged while the car is plugged in and from the main traction battery. I did replace my 12v battery after 6 years as precautionary preventative maintenance.

[Philk]

Originally Posted by Coastali8

To find your traction battery capacity just add the total of the last 5 digits of your VIN number together.
Press your trip meter reset button and hold for 10 seconds.
A menu will appear, select unlock and hold for 3 seconds. Enter the VIN total by repeatedly pressing the button.
Select from the menu TANK. Read “batt Kappa max.”
Press and hold to exit.
5.2 kWh is max usability for a pre LCI car traction battery. Your number could be a little higher if your battery is in good condition.

I can’t remember what level the “Kappa max” would have to decrease to for BMW to replace your battery as being defective. It’s somewhere in one of these threads as is the above procedure but I think it’s a lot. I believe 15-18 miles is about the standard range for a fully charged pre LCI battery, but that number is calculated based on how you have previously driven the car.

I leave my car plugged in all the time when it’s not being driven. Nearly 7 years now. No issues. The 12v battery is trickle charged while the car is plugged in and from the main traction battery. I did replace my 12v battery after 6 years as precautionary preventative maintenance.

Thank you for this. I shall give that a go

[Philk]

So, having done the check, my car was showing 5.3 KWh with a charge level of 96% (next time, I'll do the check straight after charging). For a 2016 car with 20,000 miles under its belt, I'm guessing that is quite a good reading?

[ChiTownM]

Originally Posted by Philk

So, having done the check, my car was showing 5.3 KWh with a charge level of 96% (next time, I'll do the check straight after charging). For a 2016 car with 20,000 miles under its belt, I'm guessing that is quite a good reading?

Mine is a 2014 and reads 97%, so we are both in line here with the readings. Makes me feel better about the longevity of the batteries.