ponnu

Forgot to mention, I also use 'Battery Tender' occasionally, Yes I use the same one you get it from dealers with out the logo (even at dealer's its not so expensive about $10 more ). Why don't you try that first? charge it for couple of days.. (once the battery is fully charged it should go into floating mode)..

syrousd

You are correct....like I said before it is hit and miss with after market batteries. BMW electronics and CPU is very hyper sensitive to voltage and amperage variations. You might get lucky by replacing it and it works. Also My OEM batteries last 5 years on all my cars, so if you do the math it is not a bad deal.

Obviously final decision is yours but here is my suggestion since i have replaced over 100 various batteries in these cars so far and I like to share my experience with you fellow board members!

syrousd

Yes..find someone that has a resell card and you get it for around 200 or so. Oh and all this is based on the assumption that you don't have any other electrical issues in the car so I wold check that as well.

umichchris

Pep Boys did a test for me and said that both my alternator and battery were 100% and did not need to be replaced....but i had just driven there so everything was charged at the moment. turns out i was in dire need of a new battery. honestly for the $94 just buy a brand new battery and be done with it....but im far from a mechanic lol

balbs

If the battery is not already damaged from the undercharge, try going to an independent BMW shop and see if they would register the battery for the new amperage. They should be able to do it for about $50.

donpb

Sounds like a good idea.

I just didn't want to go to the stealer.

I'll have to call around then.

I got the battery (49-72OEJ) from Kragen for $120 versus $250 OEM.

brob

I can leave my car (2008 530d LCI) parked for weeks without starting problems. However, I have had many "Increased Battery Discharge" warnings displayed. My dealer did a diagnostic check, and discovered that in the last 30 days, 49 trips were under 5km, and each journey was too short for the battery to be fully recharged. The above alarm comes on when the battery is discharged to 60% of its capacity, and is sensed by measuring the battery voltage at the moment the ignition is switched on. More amazing is the fact that all the on-board computer/control systems consume about 30 amps, and the alternator works quite hard to recharge a 60% battery and supply power for all the car's electrics as well. If you leave the ignition on without starting the engine - eg to check out how some of the car's smarts actually work - you can flatten the battery PDQ! The dealer said that the time taken for all the electrical and control circuitry to go to sleep is minimised if the car is locked. However, if the car is left unlocked after switching off the ignition (ie after pushing engine STOP button twice) some systems can take up to 8 hours to enter sleep mode. If any electrical device is turned on during the 8 hours, such as opening a door, this triggers some systems to wake up, and a new 8 hour shutdown period starts. So you should be careful if you wash your car whilst your comfort access key is in your pocket. But BMW designers are not dills either. My car is fitted with a so-called calcium battery, in which the lead in the plates are alloyed with calcium and silver instead of the more normal antimony. These batteries are sometimes called deep-cycle, because they can deliver full performance down to about 75% depth of discharge. They are designed to go for long periods without attention or charging, they recharge faster, and they last longer. So my simple strategy is to reduce the number of short trips and to keep the car locked when I'm not driving it. And if you can't do longer drives, BMW can fit an AGM battery with even better performance. They offered me one for A$1130 fitted! You can guess where I told them to put it.

vash68

This is just what I am trying to figure out - this sounds like my case: short trips (15mi each way) during the week and fully charged battery (Interstate Mega-tron Plus) lasts about 2 months, then requires overnight charging.

Someone suggested I keep my CA key more than 20ft away from a locked car. Now, what do I do while washing my car? Do I insert the key and turn ignition off or do I lock the car and throw CA key as far as possible (30ft) ?

I did notice that washing my car with CA key in my pocket is a mess - the car acts like a kid is playing with that key

Crazy stuff..