[steveog]

I have a 2009 328i sedan and looking to replace my orginal battery. Ive heard conflicitng reporting on whether I can purchase one from say, Costco, and then just install it without registering it.

Or if I need to register it, is this a DYI option?

[ctuna]

Costco carry's Interstate battery's which are fine .
My Interstate 49/H8 Megatron has been running for more than
8 years.
If you work on your car it's good to get some diagnostics.
You can go the buy a phone app like Bimmergeeks Pro Tool Route
or buy there K/D can cable and get the downloads for Standard
Tools Suite and Ista D/Plus off the Internet .
The later are more powerful tools.
Either one will allow you to register and even program battery size
within the limits that BMW allows and so much more.
Do not use battery back up when changing the battery all it
does is blow up fuses.
There are other DIY options but those are the two best .
It won't kill your car to run awhile without registering it.
There is some debate if it even makes a difference as long as the amp hours
are somewhere close to the battery you take out.
Also do not make this mistake
DO NOT CLOSE THE TRUNK WITH THE BATTERY OUT
there is a way to recover from this but you won't like doing it.

https://www.e90post.com/forums/showt...hlight=Battery

https://www.e90post.com/forums/showt...hlight=Battery

[Joanthanthaniga]

Costco Agm batteries are good; better warranty than BMW. look for someone with icarly or local mechanic to register for 30-40 bucks.

very careful as the body is negative, you might blow out the power distribution fuse and you might need to change the entire block as these fuses cannot be replaced and IBS is very sensitive too. So don't tap it or hit it. read bently service manual before you do any DYI.

[ctuna]

Do not change battery types or capacity's unless you are prepared to
reprogram the battery parameters.

[jsunma]

It may be worth your while to call your BMW dealer's parts dept and give them the part number/info from your existing (original) battery and ask about the cost of a replacement. For my 2008, that turns out to be $179...and given that the OEM batteries last me well over 100K miles and about 8 years, that seems like a pretty good deal to get something that I don't have to be concerned about beyond registering (which is simple, it's changing parameters, as Ctuna say, that causes people problems).

When I read about people chasing down all sorts of replacement batteries from Costco, Home Depot, etc, it seems like this is a case where OEM is reasonable in terms of time, effort and $.