NRG EPAC Voltage Stabilizer - P/N: EPAC-400 Product Model: NRG-EPAC-400 Charging System - Battery Doctor Connected to battery terminals, this unit stabilizes power output to all electrical components drawing power from battery. Using an independent power source, this unit boosts battery power when under high loads, thus regulating fluctuations coming from the battery that can result in loss of power or responsiveness from ignition system components. Can also improve interior lighting as well as stereo equipment performance.