[Trogster]

My M2 will be stored for a few months as I holiday abroad for winter. I plan to remove the battery and store it in a temperature controlled environment.

Just wondering if I can expect any grief when I re-install the battery?

Will the vehicle remember all its settings?

I hope I don't have to go through a reprogramming session when I re-install the battery.

[Tag]

Why not get a battery tender?

[Trogster]

Originally Posted by Tag

Why not get a battery tender?

I intend to do that as well.

[Dinosoar]

I have heard that BMWs don't like batteries pulled and putting one back in requires the dealer...I'd double check with the dealer. My friend's experience was with an E92 M3 though.

[Trogster]

Originally Posted by M2siast

Don’t you live in Richmond? What winter are you speaking of?
A battery tender will be enough with the battery in the car because of the alarm and telematics… otherwise nothing would be needed.

That's certainly an option.

As I would hardwire a tender, I would still prefer to disconnect the battery during the installation.

Again, any issues to anticipate when reconnecting the car battery?

[Tag]

Originally Posted by Trogster

That's certainly an option.

As I would hardwire a tender, I would still prefer to disconnect the battery during the installation.

Again, any issues to anticipate when reconnecting the car battery?

[Trogster]

Originally Posted by Tag

Thank you.... I did see that before.

But again, if I proceed to hardwire my tender, I would prefer to disconnect the battery for a short period while I complete the wiring.

Has anyone disconnected their M2 battery? Are there any considerations to be aware of when re-terminating?

I am aware that a NEW battery needs to be registered....with hope, that wont be necessary for this procedure.

[Trogster]

Originally Posted by M2siast

There shouldn’t be a need for anything extraordinary. I thought you wanted to leave your battery unplugged for the duration of your trip. No harm in unplugging your battery.

Just make sure you don’t close the trunk, or at least, fold the back seats.

I've done this dozens of times before, but never on a modern BMW.

I'll let you know how it works out.

[Tag]

Originally Posted by Trogster

But again, if I proceed to hardwire my tender, I would prefer to disconnect the battery for a short period while I complete the wiring.

You don't need to remove the battery to hardwire a tender, but hey, it's your car, do whatever you want.

Originally Posted by Trogster

Has anyone disconnected their M2 battery? Are there any considerations to be aware of when re-terminating?

Just be careful not to cause a short, otherwise you're just disconnecting it form the terminals. The car will log that the battery was disconnected/reconnected. The dealer will see this and it's one of flags used to check if a car was tuned. You should be fine though since you're not modding anything, but in case they ask now you know why.

Originally Posted by Trogster

I am aware that a NEW battery needs to be registered....with hope, that wont be necessary for this procedure.

Registration is only required for a new battery, you don't need to (nor should you) do that when reconnecting your battery.

[aerobod]

From https://www.bmwusa.com/content/dam/b...ver_042220.pdf

[Trogster]

Originally Posted by aerobod

From https://www.bmwusa.com/content/dam/b...ver_042220.pdf

BINGO!!

If that's the entire impact of pulling a battery, we're good!

[aerobod]

Originally Posted by Trogster

BINGO!!

If that's the entire impact of pulling a battery, we're good!

It could mean you have to incur a for-fee update to the maintenance dates at the dealer, though. Without that update you may end up not getting all the free maintenance items in the 3 year included maintenance period.

[Trogster]

Originally Posted by aerobod

It could mean you have to incur a for-fee update to the maintenance dates at the dealer, though. Without that update you may end up not getting all the free maintenance items in the 3 year included maintenance period.

If I leave the battery in-situ over winter, then it will only be disconnected for the few minutes it takes to connect the tender leads.

I trust the service clock will resume when the battery is reconnected?

[aerobod]

Originally Posted by Trogster

If I leave the battery in-situ over winter, then it will only be disconnected for the few minutes it takes to connect the tender leads.

I trust the service clock will resume when the battery is reconnected?

That would be correct, would only be a problem if you are pulling the battery for the winter. You may end up with having to do things such as resyncing the window pinch setting, though.

[Tag]

Originally Posted by Trogster

If I leave the battery in-situ over winter, then it will only be disconnected for the few minutes it takes to connect the tender leads.

I trust the service clock will resume when the battery is reconnected?

If you don't mind, can you explain why you insist on disconnecting the battery when installing the hardwiring? My curiously is getting the best of me.

[Trogster]

Originally Posted by Tag

If you don't mind, can you explain why you insist on disconnecting the battery when installing the hardwiring? My curiously is getting the best of me.

Sure...out of an abundance of caution.

The tender leads will be terminated in the engine compartment. Of course the negative lead will terminate at chassis ground, and the positive lead will terminate at the 'hot' jumper terminal.

The 'hot' positive jumper terminal is in close proximity to metal components (cross brace).

And although I have a steady hand, I would rather not risk a short to chassis when I remove the jumper stud when I secure the tender lead.

Safety first

[Tag]

Originally Posted by Trogster

Sure...out of an abundance of caution.

The tender leads will be terminated in the engine compartment. Of course the negative lead will terminate at chassis ground, and the positive lead will terminate at the 'hot' jumper terminal.

The 'hot' positive jumper terminal is in close proximity to metal components (cross brace).

And although I have a steady hand, I would rather not risk a short to chassis when I remove the jumper stud when I secure the tender lead.

Safety first

The hot terminal under the hood is just a nut that unscrews leaving exposed the thread, but the hotwire remains attached and will not come off unless you pull it off. Also, when you connect the hardwire, it should be an open circuit, meaning it's not connected to the tender yet. So even if you have the hot lead connected and the negative lead touches ground nothing will happen. In fact, I think you have more of a chance causing a short disconnecting/reconnecting the battery from the trunk.

To each their own.

[Trogster]

Originally Posted by Tag

The hot terminal under the hood is just a nut that unscrews leaving exposed the thread, but the hotwire remains attached and will not come off unless you pull it off. Also, when you connect the hardwire, it should be an open circuit, meaning it's not connected to the tender yet. So even if you have the hot lead connected and the negative lead touches ground nothing will happen. In fact, I think you have more of a chance causing a short disconnecting/reconnecting the battery from the trunk.

To each their own.

The risk lies with the spanner on the jumper stud. When in contact, the entire spanner is conductive and a potential short path.

You'll have to clarify how removing the negative battery lead in the trunk risks a short?

[Tag]

Originally Posted by Trogster

The risk lies with the spanner on the jumper stud. When in contact, the entire spanner is conductive and a potential short path.

You can just lay some towels over that area.

[Trogster]

Originally Posted by Tag

You can just lay some towels over that area.

Indeed.

I have rubber sheets that can be located in the engine bay to minimize risk. Plus I can insulate my tools with heat shrink tubing.

However if removing the battery negative terminal alleviates all risk with little to no impact to vehicle memory settings, that seems the sensible approach.

[///M TOWN]

Originally Posted by Tag

Registration is only required for a new battery, you don't need to (nor should you) do that when reconnecting your battery.

I always hardwire mine

Makes it easy to plug and unplug on the fly

[RockCrusher]

Originally Posted by Trogster

That's certainly an option.

As I would hardwire a tender, I would still prefer to disconnect the battery during the installation.

Again, any issues to anticipate when reconnecting the car battery?

I've not had a chance to observe this at the BMW dealer but it was SOP at the Porsche dealer when a vehicle was in and the battery needed to be disconnected the tech would connect 12V shop power to the vehicle to ensure no upset to any of the vehicle's electronics.

My advice would be to stop in at the local BMW dealer service department and ask if the car would need shop power while the battery was disconnected.