Bosch CTX-TAM514 Replacement Battery 3.6V 1200mAh Ni-MH

Bosch CTX-TAM514 / CT-COM Series — 3.6V Ni-MH Replacement Battery

This 3.6V, 1200mAh Ni-MH battery replaces the original pack in the Bosch CTX-TAM514 and CT-COM cordless phone range. It fits the handset directly and restores full wireless operation to the telephone system. Capacity figure is 1200mAh (4.32Wh) as rated by the manufacturer.

• CTX-TAM514, CT-COM157, CT-COM214, CT-COM316 and more: These handsets share a 3.6V single-cell Ni-MH pack with the same physical footprint — 42.40 × 49.90 × 14.40mm — and the same terminal layout, so one battery covers the full CT-COM lineup alongside the TAM514.
• Bench tested on actual hardware: We cycled this pack through charge and discharge on a DECT handset platform. The cell voltage held steady through the talk-power draw, and the protection circuit behaved correctly at both end-of-charge and low-voltage cutoff.
• First-charge conditioning on Ni-MH handsets: After installing, seat the handset in the base and leave it for a full 16 hours before first use. Ni-MH cordless batteries ship partially discharged, and a slow initial charge is what gets the pack to rated capacity — skipping it means the first few cycles will read short.

Base station showing no charge or error light on a new Ni-MH pack

Bosch DECT bases use a delta-V detection method to confirm a charge is in progress. A new Ni-MH battery that has sat in storage can drop below 3.0V, which some base units treat as a fault rather than a flat pack. The base then refuses to start the charge cycle and lights the error indicator instead. Seat the handset, remove it after 30 seconds, and re-seat it — this resets the handshake. If the error persists, a short 15-minute trickle from a standalone Ni-MH charger at the correct cell count brings the voltage back above the base acceptance threshold, typically 3.3V.

Range drops noticeably after fitting a replacement battery

DECT transmit power is constant by spec, but the RF output depends on the handset pulling stable voltage during the burst transmissions. When a fresh Ni-MH pack hasn't completed its first few conditioning cycles, internal resistance is higher than rated, and voltage sags under the RF load. This sag is what the user experiences as reduced range — the signal weakens mid-burst. Run three to five full charge-and-use cycles and internal resistance drops to spec. After that, range returns to the original baseline.