[JimD]

The ways to code for a battery change include having the dealer do it (probably most expensive), having an independant BMW garage do it, paying somebody who does coding to do it (including remotely), doing it yourself with NCSExpert and INPA, and doing it yourself with BMWhat. I didn't realize BMWhat does it but I checked it out yesterday and the android/Apple app says it will do it although it's a small add on. If you were starting with nothing, BMWhat may be the way to go. The app + bluetooth adapter seems to be equal to maybe a few dollars less than buying a good cable to use NCSExpert. NCSExpert is very powerful but not real easy to use. The videos I've seen of BMWhat look more like "normal" software. Issue a command and the software does it. Registration with the NCSExpert code set is like that but changing the battery size is the more typical (for that software) process of downloading a software module, changing it, and then reloading it.

In NCSExpert, in other words, it's a one or two step process depending on if you are changing the battery size and type. If you change from a wet cell to a AGM or you go up or down in size, you have to do two steps. One step, always required, is to tell the car the battery is new. I think that is in Tool32. The other step is to load the necessary software module to tell the car the battery size or type changed - if it did.

What battery to use is to me a personal preference. I am pretty confident there is nothing very special about the battery from the dealer, however. You need one with terminals in about the same location, however, given the somewhat unusual hookup. It also needs to be vented outside so it needs the port for that. But I don't think that's hard to find, just something to check.

I also don't think battery replacement and coding have to happen on the same day. If you charge the new battery a little wrong for a few days, it should not really impact it. If you do it for months or years, then you shorten it's life.

If you are worried about your battery, it is not hard to check. Advance Auto may do it for you if you ask. I have a little tester I bought from Harbor Freight for about $20 that does it. It is just a fancy volt meter with a resistor that can displace around 100 amps for a few seconds. You hook the meter to the battery and push a button and read what it says. You are measuring the battery voltage under load but the display give you the cold cranking amps your battery is capable of.

My 09 battery seems fine but I haven't checked it. I probably should. It sits for a few days at a time most weeks (I also drive a SUV).