745Li E65 battery replacement made easy [Archive] - Bimmerfest - BMW Forums

: 745Li E65 battery replacement made easy

05-26-2011, 05:00 PM
Ok so rather than reading through years of posts as I did and balancing thousands of opinions and confusion, here is the skinny on 745Li battery change for 2002 through (I guess) 2008.

Dealer price $600; DIY price under $200. + registration.

The car takes an AGM battery, not a standard lead acid. If it says AGM on the side you are cool, if not, don't buy it regardless of the guy at the store telling you its original equipment. I copied Keif's posts and found the only local AGM battery other than from the dealer, at O'Rielly's Auto parts for $169 Super Start - Automotive AGM Battery Part Number: 49AGM. Dealer is about $300 just for the battery. There is an online BMW dealer that had them for $230+ship, but did not spec AGM. They are probably all made by East Penn in the US - perhaps you'll find a local dealer for them. You can search for a DEKA European Performance Battery 9AGM49 - AGM Battery ($171 online). If you want to buy lead acid, then do it, but it's only $40 difference. My original AGM lasted from factory new 38/2003 through May 2011 ***8211; 'nuff said.

To replace the battery, remove the spare tire and a small hold-down bracket on the battery (torx). Remove the spill tubing from the hole in the floor. Remove the jack and the tray it is in will lift out for access to the cables. Remove cables, being very careful not to short them (likely not an issue, but ***8230;...). Remove battery, connect spill tube to new battery and reverse order. I think it was a 10mm socket that removes the battery cable lugs. 15 minutes with a helper. Don't remove any other trim. Reset the car's time and date when finished using the i-drive knob.

You must register the battery to the car ***8211; meaning you have to reset the charging algorithms of the car so it is set for a 'new' battery vs your old one. If you don't, the car won't charge it properly and the battery will fail prematurely, perhaps within a year. I believe this is critical, but do what you want ***8211; its your money.

You register the battery by going to a local foreign car repair shop, the dealer or your own by using software and the OBD port. Might cost as much as $90 for the dealer to register it, likely less at local shops and probably the lowest cost & easiest way to register it. Takes 2 minutes.

If you want to register it yourself, you have to buy some specialty cables and download the INPA software ***8211; total cost for all cables is about $50, but you can use them for other issues if you can get the software running. For laptops made in this decade, you will need a USB to RS232 adaptor (find it on ebay or Amazon and make sure it specifies a Prolific chip, then download this driver prior to plugging it in: http://www.prolific.com.tw/support/f...aller_v130.zip. Thanks be to Helf745Li and his great INPA posts). The other cable is from the RS232 adaptor to the OBD port on the car (Ebay ***8211; China). The software is free online ***8211; read the INPA posts on this site to learn about the software and cables. It took me tens tries to get INPA loaded and mostly working, taking at least 8 hours of effort even with years of PC experience. An older laptop might be easier to get it to work (Win95/98). Plus the research time spent here.

As my INPA would only speak German after getting to the sub-menu's, I followed this post's instructions (sorry I don't know your name, but THANKS!!) and it worked perfect.

Procedure to register new battery using INPA:
***8226; Step 1: select BODY from the left hand pop-up menu
***8226; Step 2: select POWER MODULE in the right hand list
***8226; Step 3: select ACTIVATE from the next menu
***8226; Step 4: Select ACTIVATE2 from the next menu
***8226; Step 5: Then select F7 - Register battery replacement in German. Almost instantly you get the message: "Register battery replacement Activated properly." - in German.

And that was that, actually not so bad after all and saved $350 from the $600 dealer price.

06-17-2011, 09:24 AM
That is awesome info. Thanks!