It depends on the settings. Some settings default to what you have now, so if there's something that gets cleared and defaults back to it's place, then no keychip necessary. These are the things off the top of my head that will need Keychip if you change battery:
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[/size]1 Sas settings for TITO (if you have a home Tito solution)
[/size]2 Paytable other than the default, which varies from game to game. (this is the game's holdback percentage)
[/size]3. Any other custom setting regarding sounds, volume level, limits, etc.