There has not a single symbol of a weak battery on the 2008 328I, built Nov 2007: It just failed to start in a normal morning after a little over 5 year service.
The battery is a white OEM, 90AH, 160RC, 720CCA. The deal asks $205for the battery and 189for installation and register (Houston area). Cost asides, a DIYer should not be daunted by a few technical terms, AKA, battery register
. Here we go:
The battery choices:
The OEM battery is secured by a long bolt with a clamp pressing the bottom edge of the battery as circled in the right side of the picture. When you take out the battery, you will see a series of sockets at interval of every 1.5” for the bolt. Therefor dimension wise the longest battery fits this car is about 14”(H8), the second largest is 12” 7/16 (H7), etc. Also it is a must to have vent on ONE side vented outside to the L shaped hose (circled on the front side of the vehicle). You have to plug the other vent on the battery if it comes with holes on both ends. Here are a few possible replacements:
1. From Dealer OEM
2. Advance Auto website insists 9RH7 is the right size, which is 1.5” shorter than size H8. both conventional and AGM come with RC140.
3. Autozone website says the H8 is the right size, the AGM type comes with RC170.
4. Walmart MAXX H8 conventional is rated RC150.
Considering the battery is trunk mounted an AGM battery is a better choice. I would also consider H7 size which is the second longest battery for easy in and out of the battery tray. However this time I have no time/experience to code a new battery so I pick the Walmart Johnson controls battery that is cheapest and most close to OEM AH.
Battery Register with free software available from smooth1 in this forum. http://www.e90post.com/forums/showthread.php?t=727091
With the computer connected to the vehicle’s ODB port, Key in the slot, apply no brake and press to turn on the car. Under the ‘special’ menu, select ‘register battery’, you will be confirmed by something like ‘ battery register was successful…’. This easy step is for reset your computer for a new battery at same spec, e.g., an OEM or a generic with similar spec.
Of course you need this $30 cable, shipped from Honkong from ebay (search BMW INPA K+DCAN D-CAN CAN INPA Ediabas USB Interface). The software installation is daunting task but following instruction is all you need to do. On the other hand, I believe you don’t need to use the software it comes with, all you need is the COM-USB simulator driver for Smooths ‘s software to work.
In terms of register the battery or leave it alone, I drove the car for 2weeks w/o register. Only thing I noticed (maybe in my mind only) is the blue tooth does not work smoothly. After register things appear back to normal. My next battery will be an AGM, I hope by then I should have be able to code the battery spec in.