The Varta battery is not needed for home use and it is highly recommended that they be removed as soon as you get any board with it. The game should boot up normally without it, if you are getting netplex errors or door open errors, then you have battery chemical damage on your board. They are difficult to fix since these are multi-layered boards and you don't know which leads are damaged by just looking at the surface. If the game works fine, then just make sure you clean up the remaining battery gunk with preferably 99% iso alcohol.