Z4 E89 Winter Storage - Battery disconnect problems?

[HowieZ4]

Hi All,

Quick question regarding winter storage and battery disconnect for a few months. Will disconnecting the Z4 battery cause any problems or faults with the car system and computers?

I store my car for 3 to 6 months each year and won't have an access to a wall outlet to connect a battery tender so trying to figure out the best way to prevent the battery from going dead and damaged from deep discharged.

Also, if I disconnect the battery from the trunk, can the trunk lock and how do I unlock it after? Is there a manual key opening for the trunk?

I couldn't find an answer from doing a search on this forum so any help would be appreciated.

Thanks!

[ManiacGT]

There is no manual unlock for the trunk therefore if you intend to remove the battery, you MUST leave the trunk open OR leave the hood open so that you can connect up jump leads to the power connections in the engine bay to power the car to unlock the trunk.

The car, unpowered for this length of time, may revert to 'transport mode', I'm unsure. Transport mode is a limited power mode for transportation purposes and you may need to have a dealer restore normal mode. However again, I'm uncertain about this and you may not have any issues at all.

Another concern is a) you should ensure that the car is well ventilated as the interior could grow mould. b) after several months your tyres could develop flat spots.

Most people leaving a car for this period will leave the battery in place and keep it on trickle charge, moving the car back and forth every few weeks to ensure brakes dont seize and tyres don't flatten etc, but as you say, if there's no power, this will be tricky.

[HowieZ4]

Thanks ManiacGT. I guess disconnecting the battery is out of the question if I can't lock the boot. Any idea how many months a good condition battery will last before it's depleted?

If the battery is totally dead, where are the connectors in the hood? Will it short out or blow some fuses with a jump start?

The other alternative is to connect a trickle charger to a 220V UPS backup battery in the trunk and hopefully that will give the car battery a few extra months of juice via trickle charging. I might go this route if all else fails. Just have to figure out what UPS size battery I need to extend the car battery for 6 months since I live half a year overseas.

My car is still under factory warranty so will BMW replace a damage battery from deep discharge?

Thanks again for your post!

[ManiacGT]

its probably worth asking BMW themselves about how best to store the car to be honest, how long the battery might last etc. There is no issue at all powering the car using the hood connections, see the owners manual for the locations to hook up the leads.

[HowieZ4]

Thanks for the pointers ManiacGT.

Searching for the terminals to jump start under the hood, I came upon a video showing where the BMW terminals to the battery under the hood and a portable battery jump starter unit that can both act as a backup battery, trickle charger, and jump starter all in one.

I needed a portable solution because I'm not near any electrical outlet. Here's the video and name of the charger.



DieHard Platinum Microprocessor-controlled Battery Charger Engine Starter

Hope this helps anyone else in the same predicament as me. Now I just have to check if there's enough space to fit this backup battery to trickle charge with the hood closed.

Keep up the fantastic forum support!

[morfinx]

I think BMW sells a battery charger. Check with your local dealership's parts department.

[HowieZ4]

Thanks morfinx.

I have the BMW/CTEK battery charger but my problem is my car is not parked near any electrical outlet, hence the need for a portable battery charger.

Have a good day!

[Edlogix]

A backup UPS will not last for 6 months. The backup started is probably designed to provide just high power for small amount of time (jump start)

Your best bet will probably be an additional regular battery connected to the jump start terminals under the hood. (In this case you'll have to keep the hood opened).

I've left mine parked for 2 months with no issues at all, but to be honest with you for 6 months I'll definitely unplug the battery and then deal with the reprogramming with the dealer. Electronic circuits usually go crazy with low voltage.

[snk]

Disconnect the battery and close the trunk.
Close and lock the door using the key manually.

When weather gets good, use the key to manually open door, open the hood, and you can open the trunk by simply connecting jumper cables.

[HowieZ4]

Thanks guys, will consider both suggestions.

Edlogix, rather than connecting an additional regular battery to the terminals under the hood, would it be possible to connect it to the terminals in the trunk with the installed battery in tandem?

Will it cause a surge in voltage and damage to the car electronic? This way I can close the trunk securely instead of a partially open hood.

snk, if I disconnect the battery, will the Z4 trunk latch lock securely without the electric assist? Or will it lock but with a slight gap remaining?

Thanks for all your help!

[Edlogix]

Leaving a regular battery inside the trunk doesn't seem like a good idea, batteries produce gases and some times leaks too.

As I understand that leaving the car closed is a big concern for you. Here's what I will do:

1. Close the car
2. Unplug the battery
3. Close the trunk.

When you get back:

1. Open the car with the key
2. Open the hood and plug your portable battery charger
3. Open the trunk using the button inside the car.
4. Plug the battery
5. Try to start the car

I'm not sure if the car will turn into transport mode, however you will probably have to take it to the dealer to erase the error codes produced by disconnecting the battery.

[snk]

I didn't get any error codes the last time I had my battery disconnected. But then it was only for a few hours while I worked on the car

[snk]

Originally Posted by howiebcn

Thanks guys, will consider

snk, if I disconnect the battery, will the Z4 trunk latch lock securely without the electric assist? Or will it lock but with a slight gap remaining?

Thanks for all your help!

There is a small gap but the trunk is secure, unless someone use a metal bar to pry it open, in which case there's nothing you can do when an individual has bad intention.

I know it's secure as I didn't plan for it to happen. I was working on the car, disconnect the battery and closed the trunk as it was annoying to see it wide open. When I was done, then I realized there was no way of accessing the trunk without using a secondary battery or jumper cable to give the car enough juice to open the trunk.

In other words, as long as the car is securely locked, it should be safe

[HowieZ4]

Sounds good Edlogix. As is, my car has been sitting in winter storage for 5 months now so the battery is probably flat or damaged!

Learning from all your post, my best option is to jump start my car with the portable battery and drive to a dealer for a new battery if the installed one doesn't hold a charge anymore.

For my next long term storage, I'll give the battery disconnect a try and deal with the reprogramming at the dealer and hope the car doesn't go into transport mode.

I wonder if my Cobb Tuner can clear the battery disconnect code as it's capable of clearing engine codes but not sure about electrical codes.

snk, I'll check out how big the gap of the semi locked trunk and see if I'm comfortable to leave it for a few months like that. Maybe I can hook up the portable battery under the hood, disconnect the trunk battery, and see if I can engage the trunk to close fully powered only by the portable battery.

Thanks again for the great support from this Z4 forum community. I'll update this post once get back to my car in about 2 months. Cheers!

[CeEl]

In your case, I wonder if it wouldn't be better to talk with the dealer and see if they will store it for you (or let you park on their lot), move it occassionally and hook it up to a charger every now and then ...

[HowieZ4]

Thanks ceLl. On shorter trips I'll ask my local BMW dealer but 6 months winter storage is best kept in my garage lock and secured.

My concern was having to reprogram and error codes once the battery is flat but the portable battery jumper and battery disconnect to prevent deep discharged and damage seems the best option for long term storage.

Thanks all for your advice!