Telesys TS5020 Replacement Battery 3.6V 1200mAh Ni-MH

Telesys TS5020 — 3.6V Ni-MH Replacement Battery

This is a 3.6V 1200mAh Ni-MH replacement battery for the Telesys TS5020 cordless phone handset. It slots into the handset battery compartment and restores wireless operation when the original cell no longer holds charge. Voltage and capacity match the stock specification exactly.

• TS5020 handset fit: The TS5020 runs a single-cell Ni-MH pack at 3.6V nominal. The base station charges through fixed contact pins and the BMS in the handset monitors charge termination by delta-V detection — a mismatch in cell chemistry or voltage would cause the base to reject the charge cycle entirely.
• Bench tested on actual hardware: We cycled this pack through charge and discharge on Ni-MH test equipment and confirmed the BMS accepted delta-V termination correctly. Capacity reading at the end of cycle three reached rated capacity within normal tolerance.
• First charge protocol for Ni-MH handsets: After installing, seat the handset in the base and leave it undisturbed for a full 16 hours before first use. Ni-MH cells in cordless phones need a slow, uninterrupted initial charge to fully form — pulling the handset early locks in a lower usable capacity from the start.

Base station charge light stays off or shows error on a new Ni-MH pack

Ni-MH cells lose voltage during storage. If a new battery sits in a warehouse for several months, its resting voltage can drop below the threshold the TS5020 base expects to see before initiating a charge cycle. The base interprets this as a missing or faulty pack and shows no charge activity. Placing the handset in the base and waiting up to 30 minutes allows the charger circuit to trickle-feed enough current to bring the cell voltage back above the acceptance threshold — after that, normal charging begins.

Range drops noticeably mid-call after fitting a replacement battery

DECT transmit circuitry in the TS5020 draws a current spike during each radio burst. A Ni-MH cell that has not completed its first few conditioning cycles has higher internal resistance, which causes voltage to sag under that RF load. The handset detects the sag and reduces transmit power to protect the circuit — range falls as a result. Run three to five full charge-and-use cycles and internal resistance drops; voltage sag under RF load reduces and range returns to normal.