Maintenance-free StromTank products, manufactured in Germany, eliminate all AC-born pollution, regardless of source, by converting AC to DC, storing it in their computer-controlled rechargeable lithium iron phosphate (LFP) batteries, and then converting it back to clean AC during playback. Models range from the S 5000 High Power, S 4000 Pro Power, S 2500 Quantum, and S 1000. The larger the StromTank, the more power it can output for longer periods of time. When batteries near depletion, the unit automatically switches to wall current and recharges without interrupting playback. Average autonomous operating time oper-8 hours, depending upon the StromTank model and total energy consumption of connected components.