Stromtank S-4000 ProPower MK-II XT computer-controlled battery power source
In my enthusiastic 2022 review of the Stromtank S-1000 ($16,900), I described the Stromtank as a computer-controlled lithium iron phosphate (LiFePO4) battery array that, coupled with its AC inverters and all the trimmings, supplies clean, constant, stable off-grid AC power to hi-fi components. By softly depressing a single button on the front panel, Stromtank owners can easily switch from wall-connected mode (when the Stromtank's dimmable front-panel meter is blue) to a disconnected, battery-only state (when the meter is green). At the end of a listening session, users can return to blue mode to recharge the battery array.