Normal battery could use for 4 days or above. According to your information, the battery should be used for more than half year. In Yahoo HK bidding, a HK PDA half year second hand full set with two battery, two stylus selling in about 2400 to 2500 HKD but in 90% new. Be hornest, the Treo 650 mentioned above should sell not more than HKD$1600.