The Intel® Galileo Board Gen 2 uses a 12V power supply but a power supply ranging from 7V to 15V can be used without problem. The portable charger you are suggesting will not work with Galileo Gen 2 because it's rated as 5V. You can check the following document to get more details about this topic: Intel® Galileo Boards Power Supply.
About battery alternatives, you can use a portable charger but make sure it meets the Galileo Gen 2 requirements.
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