Unfortunately , I am not aware of a separate device that can be added to an existing product to to the fuel gauge function . That is because the fuel gauge function is something that , if it ' s implemented , is always integral to the product that uses the battery . For example , a cell phone integrates the fuel gauge function in its software a laptop computer as well . A computer server integrates the the fuel gauge function in the UPS the battery . So , either a product doesn ' t have any fuel gauge function , and it ' s not expected that a user like you would want to add one to it or , a product does have the fuel gauge function built in . I want to build a Camera Stabilization deviceIf you ' re designing your own product , then you would design a fuel gauge function into its battery , either in software , or using a specialize fuel gauge IC from Texas Instruments . Look up fuel gauge in the Texas Instruments website .