[m@rco]

My car's (E90 328i MT, manuf date 11/2006) first battery is starting to show signs of weakening. A few seconds after switching off the car, the amber battery light comes on. Also, when parked with the parking lights on, the amber light will come on after about 20 seconds. Radio etc. will also no longer stay on when the car is fully switched off. Not too bad a performance after almost 8 years...

The dealer quoted me a new 90Ah AGM (Absorbed Glass Mat) battery for €450 (~$600 installed!)... I'm not sure why I am being quoted an AGM battery. I don't have one now.

My dad's E39 528i has a 70Ah battery for basically the same 3-liter engine. Given the relative mild climate where I live (and the occational skiing trip in the cold Alps), I'm considering to buy a 70Ah for my car now. Internet price for a German, quality brand, Varta battery including shipping is ~€135 ($180).

Anyone experience with downgrading from a 90Ah to a 70Ah battery?

I plan to install the new battery myself. And I will have the battery registered at the dealer (~$50). Will the 15-min ride from home to the dealership harm the battery (charging program is not set for 70Ah yet)?

Thanks for the advice!

[fazman]

Originally Posted by m@rco

My car's (E90 328i MT, manuf date 11/2006) first battery is starting to show signs of weakening. A few seconds after switching off the car, the amber battery light comes on. Also, when parked with the parking lights on, the amber light will come on after about 20 seconds. Radio etc. will also no longer stay on when the car is fully switched off. Not too bad a performance after almost 8 years...

The dealer quoted me a new 90Ah AGM (Absorbed Glass Mat) battery for €450 (~$600 installed!)... I'm not sure why I am being quoted an AGM battery. I don't have one now.

My dad's E39 528i has a 70Ah battery for basically the same 3-liter engine. Given the relative mild climate where I live (and few skiing trips in the cold Alps), I'm considering to buy a 70Ah for my car now. Internet price including shipping ~€135 ($180).

Anyone experience with downgrading from a 90Ah to a 70Ah battery?

I plan to install the new battery myself. And I will have the battery registered at the dealer (~$50). Will the 15-min ride from home to the dealership harm the battery (charging program is not set for 70Ah yet)?

Thanks for the advice!

Dealer is probably quoting you a different battery so that he can up charge you for the service to "re code the car" for the different type of battery. If I were you, I would just get another "like" battery of the same AH/RC (Reserve Capacity) and non-AGM battery which will last you another 8+ years for a fraction of the cost of the dealership rate.

As long as you drop in a battery of a similar Reserve Capacity, you do not need to re-code the car (all you need to do is "register the new battery" which is simple and free to do with the BMWLogger tool and a cheap $30 ebay coding cable).

What is the AH and Reserve Capacity of your original battery and is it a white housing BMW battery (non-AGM) or a black housing BMW battery (AGM)??

I will guide you on which kind of battery to replace it with and you can self register it at a bargain rate.

[Meeni]

Go to Walmart or whatever and buy the cheap equivalent battery. Install yourself. You still need to have the battery registered with the computer, so find an independent shop that can do it for you. Overall you should pa $200 for battery+registration doing that way.

[m@rco]

My current, white, battery specs:
12V 90Ah 720A
160 RC 720CCA

I was looking to replace with a VARTA SILVER 77Ah(20h) CCA 780 EN. Not sure about the RC... Couldn't find it on their website...

About the BMWLogger tool... I've thought about that. Just not sure which one to get (here in Europe or better The Netherlands) and not sure how to program the software. Any help would be appreciated, especially if I could use that tool for reading other errors/resetting etc.

Thanks!

[m@rco]

Latest update: bought and installed a Varta Silver Dynamic 85Ah 800CCA for €130 ($170) and installed it myself. BMW dealer registered the battery for €25 ($32). A similar battery at the dealer (also non-AGV) would have cost me $100 + labor more.

Only downside is that the battery is slightly smaller so doesn't fit perfectly under the black positioning bar. Will have to place a piece of plain wood to close the gap and prevent the battery from coming loose from the bottom. Otherwise battery and car running fine. In hindsight, I could have gone for the exact same Varta capacity battery with BMW Exide battery's dimensions. Too late now but the current size did save me €20.

Needless to say: exchanging the battery is doable but a pain-in-the-neck (read: pain-in-the-back) job due to the small location and difficulty to keep the wires out of the way when putting the new battery in.

[techie182]

So batteries don't have to exact match to register? Any similar rate will work?

[thomas88162]

Hint: It is very helpful to have INPA/DIS software for these cars. It makes the dealer feel a lot less important.

[m@rco]

Originally Posted by techie182

So batteries don't have to exact match to register? Any similar rate will work?

Correct. The dealer (or you) can adjust the settings of your car so that it can handle higher (upto 100Ah - if i remember correctly) or lower amps (minimum 70Ah - if i remember correctly).