old battery was low ( but not dead) so i bought OEM from the dealer. Plus the old one lasted me like 7 years . anyways the reason i am posting that i was reading online and on youtube that before and after changing the battery one need to do some kind of calibration ( like turn the key on II position or open and close the sunroof couple of time etc) in order to reset the computer.
But when i read the owners manual on my 2006 S80 2.5T there was no mention about this at all.
Its just a simple remove the old one and put in new one
And thats what i did with no problems. The car started up just fine and there was no problems in electronics in the car.
I was going to do a DIY but its actually pretty straight forward.

 

akabond, thanks for update. I changed mine last month but soon after changing i am facing issues...like some times when my car is warm enough or 100 KM drive after...though I changed exactly the way you did......but when I turn off the car and start again, my RPM zooms up and down....any suggestions?

 

looks like yours is a different year and engine. did you read the manual about any calibration and/or talked to the dealer just to get their opinion about replacing battery. i had to ask the dealer too when i was there to get the new battery and they 1st asked what kind of engine. so maybe that might be a factor.
But you said after a month. so could be something else. You only mentioned that the issue is rpm goes up and down. that could be some minor electronic signal . mine did that too but on my old battery and it was random. With the new one it stopped.
As you know older S80s have lot of electrical problems

 

I also just changed out the battery in our '06 S80 2.5T. I turned off the A/C system and the radio. The radio worked with no code needed and A/C blew cold air. No problems in over a week.

 

We got winters here from few days its working fine, so I am sure either my Starter cables are culprit or Starter it self. Thanks.