Vehicle settings lost when replacing 12v battery ?

Some in the past have hooked up small battery (I forget what maybe a 9v ?) to keep the settings.
But I just disconnect and lose the settings.

 

I believe the service manual does suggest jumping another 12v battery while changing the old one. Got to be careful or a crossed jump could cost you more than just the settings. The only one that makes a difference to me would be the radio presets although a few like all doors open from drivers would have to be redone as well. In some cases, starting with a hard reset can be a good thing for computers in the car.

 

I use a jump pack with 12 volt accesory outlet, and plug into it a chord with a special obd connector at the other end: it just has a few pins, the ones that connect to 12 volt. This chord also has indicator light, so you can verify your connections are good. Hooked up, you can then remove/replace your 12 volt battery, and the car's none the wiser.

I've actually got a couple of the cords, this is one of them, but they're fairly common:

Memory Saver Cord - ESA30 | Call us at 1-800-328-2921 | Clore Automotive

I've occasionally (purposefully) disconnected the 12 volt, doing brake work, just no way to avoid it, and this is what I've found:

1. Radio presets gone.
2. Trip meters lost.
3. Displays reset to defaults.
4. Window auto up/down sometimes lost.
5. Odd behaviour on start up, the next few times: excess rev-up, like the car is relearning throttle response or something.

 

If you pick up one of those OBD memory saver cables, use it with your jump pack, that would be ideal. They're about $20.

I'm not sure, but I suspect what you're proposing is doing exactly the same thing. Maybe someone with more electrical smarts will comment.