Available in two versions, the Palmer Bat Packs are purpose-designed to power multiple stompboxes and pedalboards. They feature high grade, long-life lithium polymer batteries providing 500 mA each from two 9 volt DC center negative barrel outputs that are fully regulated. Recharging the 4,000 mAh capacity Bat Pack 4000 takes approximately four hours and twice that for the 8,000 mAh Bat Pack 8000. Both come in low-profile all-metal enclosures with 5-segment battery status indicators and convenience type A USB port for charging smartphones or tablets. Run time depends on your pedals' current draw.