Can I buy an Optima battery for my 2008 S40?

 

You should be able to find one for it.

 

How would I know if it would work or not? and also dont you need a code for the radio if the battery is disconnected?

 

Measure your current battery then find one with the same size or smaller and with the same top mount or side mount poles. Get the red-top regular battery not the yellow-top deep cycle battery. This article deals with charging a dead one: How To Charge an AGM Battery - Hot Rod Magazine

You have a radio code in your 2008? I don't think my 2005 has a code as there is no way in hades you can remove the radio and install it in any other car. (being it's part of the "waterfall" center console and has the climate control built-in.

 

There are some special instructions for changing the battery. See my post in this thread: https://volvoforums.com/forum/volvo-...acement-52807/
Stan