There's really no reason to risk doing that with the power on. Back up the unit, swap the battery, restore the unit. Easy going, no risk.Unless you backed them up they are gone forever. If you change the battery you have to do it with the unit on.
WARNING: Don't do this if you don't know what you are doing. The power supply section will obviously carry a mains voltage.
CONTACT WITH THIS SECTION COULD CAUSE DEATH OR SERIOUS INJURY.
I changed the batteries in both my ultras when the units were on.....I covered the power supply section with a plastic sheet as a precaution against my clumsyness. Wearing a wrist strap is a good idea to prevent static damage to any of the components. While there are no mains voltages after the power supply.... if you can't identify this section don't do it.
The battery just slides out and can purchased just about anywhere.
BACKUP BACKUP BACKUP is the rule. Sorry you lost all your presets but there are some brilliant presets around by Yek and many others.
True.....I did it because the backup process on the ultra was buggy and took several tries and changes of speed and buffer to get it to reload. There's not a great risk to people with training or and experience in electronic repair.........but if you dont know what you are doing then the safe way is to follow your advice.There's really no reason to risk doing that with the power on. Back up the unit, swap the battery, restore the unit. Easy going, no risk.