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replacing the backup battery of Ipaq hw6500 series do not require soldering.
there is a video at www.repairHPpda.com showing how to replace it
hw6900 series require soldering but backup battery of hw6515 and hw6510 does not require soldering
as you can see the photo of the backup battery at below link, the backup battery looks like a watch battery, there are no pins for soldering
http://www.repairhppda.com/product_info.php?pName=backup-battery-for-hw6500-series&cName=select-your-ipaq-model-hw6500-series&osCsid=68d28a717cc263469a1aad3e72f4ffc3