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Great question! The Portable Home Speaker is able to support a maximum power input of 5 VDC, 3 A. Due to this, a fast charger would no be recommended as it may damage the speaker. A fast charger typically runs at 20V with 5A meaning it would be far too powerful.
However, the speaker does have up to an incredible 12 hours of battery with a 4 hour charge time. It also comes with the possibility to add a charging cradle. So the need to charge your speaker will be eliminated as it will always be fully charged. Just place the speaker onto the cradle at the end of each day, for another day of wireless listening.