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GPSMAP 66i and 67i Battery and Charging Specifications

For charging purposes using any commercially available charger that charges USB devices should be fine to use on the GPSMAP® 66sr, 66i or GPSMAP® 67, outdoor handheld. The battery is not removable or replaceable. 

Battery Specifications:

1 battery, 1 cell, 3100 mAh at 3.8V

Battery - containing product information data sheet