A hobbyist dissected the proprietary Sennheiser BA2015 battery pack used in many of the brand’s wireless microphones and rebuilt it from off‑the‑shelf parts. The original unit costs $80‑$100 and houses two Ni‑MH cells, a temperature sensor, and a chip that prevents charging non‑rechargeable AA batteries. By reverse‑engineering the case and circuitry, the maker demonstrated a cheaper alternative for field recording and stage use.

The teardown revealed two cells oriented oppositely—one flat‑top and one button‑top—joined by a metal strip. A tiny 10kΩ NTC sensor monitors temperature, while a third contact signals whether a genuine pack is present. The author 3D‑printed a new housing, rotated it for better layer strength, and used a bent paperclip as a low‑cost bridge between the cells to maintain alignment and electrical continuity.

Component costs drop dramatically: Panasonic Ni‑MH cells run under $3 each, the NTC resistor under $0.20, and bulk plastic filament is a few dollars. Assembling five copies costs under $30, far below the official price. While the DIY pack lacks the durability of commercial third‑party units, it proves the official design is overpriced and easily replicated for hobbyists who need reliable power on gigs.