A Powershell module can detected encoding automatically. And can transcode file to other encoding. It is powered by UTF-unknown. Based on Mozilla Universal Charset Detector.
#Get files encoding with wildcard.
Get-FileEncoding *.txt
#Convert files with wildcard.
Convert-FileEncoding *.txt -SourceEncoding "shift-jis" -NewEncoding "utf-8" -OutputWithBom
#Auto detect and convert
Get-FileEncoding *.txt | Convert-FileEncoding -NewEncoding "utf-8" -OutputWithBom