Replacement Battery for Large VoiceBooster & Aker Voice Amplifiers This is a 7.4volt, 2000 mAh Lithium ion rechargeable battery. Only one is needed per amplifier. The VoiceBooster brand is owned by TK Products, LLC. Each VoiceBooster product comes with a 6 month parts and Labor Warranty that is serviced by TK Products, LLC. The VoiceBooster must be purchased through TK Products or one it's authorized dealers for Warranty Claims to be honored. Buy with confidence!