About this replacement
Casio QT-6000 / QT-6100 / QT-6200 / QT-6600 — 3.6V Ni-MH Replacement Battery (HHR-21H3G1B)
This 3.6V, 2000mAh Ni-MH battery replaces the OEM pack in the Casio QT-6000 series portable payment terminals. It fits the QT-6000, QT-6100, QT-6200, and QT-6600 models. All four share the same battery bay, connector pinout, and charge circuit — one part number covers the range.
- QT-6000 series platform fit: Casio built the QT-6000, QT-6100, QT-6200, and QT-6600 on a common chassis with an identical 3.6V battery rail and the same BMS handshake protocol. This replacement matches that voltage and connector geometry exactly — no adapters, no wiring changes.
- Bench tested on actual hardware: We cycled this cell through the QT-6000's charge IC and verified the BMS accepted the new pack without fault codes. The charge controller completed its top-off phase normally and the terminal logged a full capacity reading after one complete boot-charge cycle.
- First deployment tip for POS terminals: After installation, run one complete transaction cycle — receipt print included — before putting the terminal into a live queue. The QT-6000 maps battery capacity during normal operation and won't display an accurate charge indicator until it has completed at least one full power cycle under real load.
Terminal not completing PCI boot sequence after battery swap
The QT-6000 runs a PCI compliance check during every cold boot. On a freshly installed Ni-MH cell, the terminal's BMS handshake can time out if the cell voltage hasn't stabilised above the boot threshold — typically around 3.4V measured at the connector. This causes the boot sequence to halt before the payment application loads. Fully charge the new battery before the first power-on, then allow the terminal to complete one uninterrupted boot cycle.
Terminal won't power on after sitting unused in a drawer
Ni-MH cells self-discharge at roughly 1–2% per day at room temperature. A QT-6000 left unused for several months can see its cell drop below the BMS recovery threshold — around 3.0V — causing the terminal to appear completely dead. Connect the terminal to its dock or AC adapter and leave it on charge for a minimum of 4 hours before attempting to power on. If the charge LED doesn't activate within 10 minutes, check the dock contacts for corrosion and clean with isopropyl alcohol before retrying.