Garaging X5 for 3 months - disconnect battery ?
 

Hi,

I'm having to garage my X5 3.0D (Nov 2002) for 3 months and wondered if disconnecting the battery will cause any problems when it is reconnected. If I don't disconnect it I assume it will go flat in that time since I will not be around to charge it occasionally.

A chance it will be quite discharged, even after disconnect or removal, 3 months later. No opportunity to run a maintenance type charger, connected under the hood lugs, while you are gone?
GL, mD

No, I don't want to risk leaving even a trickle charger plugged in while I'm away. So my question is, would it be better to disconnect the battery even if I have to recharge it (which I assume I will need to do anyway) on my return, or should I just leave it connected and let it run flat ? If I disconnect and recharge before reconnecting, will it cause any problem with the electronics on reconnection ?

Disconnect it and leave the tailgate open so you can hook it up when u get back. I would leave the tailgate open regardless. You can lock the latch on the locking mechanism and it will turn off the lights.

I would change the oil/filter in it before leaving also.

Trickle charge is the best. Battery tender

IF you can I'd really suggest a CTEK3300 battery tender.
not a trickle charger, but a battery tender.

you can even set this model of battery tender to de-sulfate your battery, and it prolongs the life.

I store my 850i for 4-5 months, during winter, under a secure parking garage 30 kms from my house and this battery tender has NEVER caused me issues. Ive been using it the last 3 winter seasons.

not expensive to buy, and not expensive to run/on electricity. Only kicks in when needed. Research it if you can.

OH but if you have to leave the batt unattended, then you just need to think about what will be easiest for you to recharge the batt in the future.
do you have the option to charge the batt while in the vehicle, OR is it easier to charge the batt if its sitting on a bench?
Only reason I say, is cause after 3 months, the batt will 99% be dead, and you may as well just leave in the X and charge it when time comes, instead of removal/re-install of it.
Just make sure, as "mywidebody02" said, to keep doors unlocked or a tail gate open to ensure access to batt (if removal/re-install is way you go).

My X5 stayed in a garage for 2 full months this winter ( November and December) with temperatures mostly minus 18 c .
never above minus 5 c . fired it up on new years day no problem at minus 5 c .
bum was a bit cold on frozen seat for a few minutes but it soon warmed up . since then only run it one day every one or two weeks . battery is 10 months old .

We've got an E46 which is treated the same way and I leave it connected to a CTEK battery charger/conditioner. If you don't want to go that route then you should disconnect it completely. Car batteries do not like being 'Deep Discharged'. I've never bothered with oil and filter on the three or four month break in use, but if it was 6 months or longer then I would.