Originally Posted by Brad from the OC
When I bought the battery, I had no idea that amp hour info was needed to register the battery. From looking at the various threads regarding purchasing non BMW batteries and registering, it appears that other OPs have bought American manufactured batteries and had it registered. What I don't know is what types of tools all of these people are using to register the battery. A description from people using a Bav Tool, say you just go to the screen and click on register and say nothing about needing or entering AH data. I wonder how many people are getting their cars registered incorrectly because the service people are just guessing Amp Hours?
I just changed my battery on the weekend in my 2007 E90 because my coding cable arrived last week.
I installed a Deka 9AGM49 battery, which is an "Exact OE fit" group 49 battery with ~95Ah and ~900CCA. I looked at a bunch of the coding howtos but, in my opinion, none of them got it quite right. Each was missing a part of the process and combining everything together was what I felt was most correct.
1/ physically swap the battery - piece of cake, exact fit, no issues
- disconnect negative terminal
- disconnect IBS data line and positive post sampling connection
- remove cross brace above battery
- remove positive post connection (including the entire distribution block
- disconnect the large positive lead that clicks into the distro block
- disconnect the bolt-in positive lead which connects into the rear of the distro block
- move the positive and negative wire harnesses out of the battery cavity
- remove the battery hold-down (Philips or nut driver)
- exchange the battery, reverse steps to reinstall
2/ Update the VO/FA to remove -B090 (90 Ah wet cell) and add -A090 (90 Ah AGM). Push the VO/FA to CAS and FRM
3/ Recode CAS (normal coding, not VO) battery type from "90ah" to "90ah_agm"
4/ Use toolset32 to register the new battery
5/ Use INPA to read the IBS status pages, you'll now see the current battery capacity listed is "91.0" instead of "90.0" (I believe they use the offset of 1 to tell the tech that it's set to AGM mode instead of wet cell mode).
Most write ups have EITHER re-coded CAS *or* updated the VO. I believe both are necessary because in general I found follow up requests for help saying that others trying to follow the howto were having trouble.