Bose recommends a current rating of 1A (or 1000mA) or higher for optimal charging. If your charger's amperage is lower than this, it may cause the speaker to charge slowly or not at all.

The Bose New Soundlink Flex is a portable outdoor speaker with 12 hours of battery life, a booming sound, and a solid ...

That means you can take it on a full day trip without hunting for a charger ... the Bose SoundLink Flex is a pretty great find for anyone who needs a tough, dependable speaker.