The charging current of the MAX1873 circuit is read through the sense resistor connected between CSSP and CSSN, so if your circuit is charging at a current lower than what you have set it is possible there is a fault with how you are connecting the Sense resistor. It is important that you follow the guidelines for connecting these pins as described in the datasheet such as connecting CSSP directly to Vin and that you connect the sense resistor as close to the IC as possible to minimize trace resistances that could cause offsets in current readings.