How do I replace the batteries on my Norelco Spectra 8845XL shaver? I read somewhere that they need to be soldered on. That's not a problem, just want to make sure I do it correctly. Also, where can I purchase the batteries? Thanks.

You will find the correct battery type for model 7865XL at shaveroutlet.com. See link below.

http://shaveroutlet.com/shaver-replacement-parts/shaver-battery-pack-for-most-norelco-more-p-278.html

To replace, you will need to remove the back cover by removing the two screws. You may need to extend the long hair trimmer to get to the second screw. Take off back cover to access inside. For easier replacement, it is sometimes suggested that you use a modified installation technique. This is to break the tabs off of the old batteries with small needle nose pliers rather than unsoldering them from the circuit board. This allows the old batteries to be removed but leaves the tabs attached to the circuit board. You can then solder the tabs from the new batteries to the old existing tabs
If you are not able to do this yourself, you can have shaveroutlet.com do it for you. See link below
http://shaveroutlet.com/shaver-replacement-parts/professional-battery-replacement-for-most-models-p-374.html