About this replacement
Optoma PK201 / PK301 — 3.7V Li-ion Replacement Battery (BBPK3ALIS)
This is a 3.7V 1350mAh Li-ion battery for the Optoma PK201 and PK301 pocket projectors. It slots into either unit and restores wireless operation for mobile presentations away from a wall outlet. Capacity matches the original 5Wh specification.
- PK201 and PK301 compatibility: Both models share the same battery bay dimensions, connector pinout, and BMS handshake protocol — 65.00 × 38.50 × 5.50mm cell footprint with identical charge termination voltage. One part number covers both units.
- Bench tested on actual hardware: We cycled this battery through the PK201's internal charge circuit and confirmed the BMS accepted charge termination correctly and reported state-of-charge accurately on the projector's battery indicator.
- Lamp brightness and draw management: Set the PK201 or PK301 to eco mode when running on battery. Full brightness pulls 30–40% more current from the cell than eco mode. In most presentation environments, the visible difference is negligible, but the current draw difference is not.
Why the PK201 shuts off before the battery indicator reaches empty
The LED lamp module in the PK201 requires a higher minimum supply voltage than the projector's low-battery cutoff threshold is set to catch. When the cell drops below roughly 3.2V under the lamp's load, the projector loses the voltage headroom the lamp driver needs and cuts power — even if the battery indicator still shows a bar or two. This is a lamp driver voltage floor issue, not a faulty battery. A fresh cell with full capacity reduces how quickly you hit that floor.
Battery indicator shows full but projector won't start
A deeply discharged Li-ion cell can sit below the BMS re-initialisation threshold — the projector sees a connected battery but the BMS has locked output to protect the cell. The battery indicator reads incorrectly because the projector is sampling open-circuit voltage, not a live discharge load. Connect the projector to mains power first and leave it on charge for at least 15 minutes before attempting to boot on battery alone. If the BMS recovers, the indicator will reset; charge to 4.2V before the next battery-only session.