MPF Products BA 150, BA 151, BA 152 Rechargeable Battery Replacement Compatible with Sennheiser IR and RF Wireless Headsets (Compatible Models Listed in Description Below)
Sennheiser BA 151 Rechargeable Battery for Wireless Headphones | Reverb
Replacement Sennheiser Electronic BA151 Wireless Headset Battery | Battery Mart
Amazon.com: AvimaBasics Premium Rechargeable Batter Compatible with Sennheiser Headsets BA151, BA150, BA152, RS-45, is 150, Fast Charging, Compact Design, Long Lasting Life (60mAh, 2.4V, NI-MH) : Electronics