First, did you call your local BMW dealership’s PARTS department to get a price quote for the 105AH BMW battery? I replaced mine in Jan/2023 and my local dealer sold it for $236. With my BMW CCA discount and core charge return…I was out the door for $227.
The only aftermarket 105AH AGM battery I cold find locally was one sold at Batteries Plus…but it was also the most expensive of all the 100AH & 105AH batteries…at over $300+.
In regard to the AH coding in Bimmercode…if your battery’s exact AH rating is not listed…simply select the rating that is closest to the battery you’re installing. A 100AH battery can use the 105AH coding. A 90AH/92AH/95AH can use the 90AH coding selection.
In regard to the vent tube…you pull the little black elbow out of your old battery and reuse it along with the car’s gray vent tube. Sometimes (like in my case) the BMW battery came with both a new little black elbow and an additional plug to insert into the vent hole on the other side of the battery. If you go aftermarket battery, they usually have a knock-off plug built into one of the battery posts covers. So don’t throw your covers away until you’ve remove the plug to insert into the other vent hole in your battery.
If you’re aux battery doesn’t have an IBS on its negative battery cable….then it doesn’t need to be registered. If it does have an IBS (intelligent battery sensor), then when you open your BIMMERLINK app to register the new replacement battery, the app should see it/recognize it and offer you a selection for registration. The aux battery in my f06 didn't have an IBS so it didn’t need to be registered when replaced. It is managed by the PCU (power control unit).
Just an FYI for those that don’t know…CODING & REGISTRATION are two different things. You only need to code a battery if you change its type and/or size. In the scenario where you’re installing a new battery and your old one was a 105AH AGM battery and you replace it with a 100AH AGM battery…then you don’t need to code the battery change because they are basically the same type and size. BUT…you will need to REGISTER the new battery.
In the pics below you can see the car’s (gray) vent tube and the old little black elbow that facilitates connecting the vent tube to the battery…I didn’t need to use the new black elbow that came attached in a little plastic baggy…but I did have to use the new additional plug (it was black just like the elbow piece) to insert into the other vent hole on the opposite side of the battery. This prevents any off gasses from the battery from filling the enclosed battery compartment. Any off gasses are carried to the exterior of the car through the gray vent tube.