Siemens 240 Cordless Phone Compatible Battery 3.6V 1200mAh

Siemens 240 / 242 Series — 3.6V Ni-MH Replacement Battery (B-7010)

This is a 3.6V, 1200mAh Ni-MH battery for Siemens cordless phone models 240, 242, CS240, and CS242. It replaces OEM part B-7010 and fits directly into the handset battery bay. Capacity is rated at 4.32Wh — identical to the original spec.

• 240 and CS240 series fit: All four models — 240, 242, CS240, CS242 — share the same 3.6V single-cell Ni-MH pack with matching connector orientation and footprint. The B-7010 part number covers the full range.
• Bench tested on actual hardware: We cycled this pack through charge and discharge on the 240 platform. The handset accepted charge from the base without error, and the BMS held voltage within the expected Ni-MH discharge curve across multiple cycles.
• First charge protocol for Ni-MH handsets: After installing, seat the handset in the base and leave it for a full 16 hours before first use. Ni-MH cells in cordless phones need a slow first charge to reach rated capacity — skipping this is the primary reason users report short talk time out of the box.

Base station showing a charging error after fitting a new Ni-MH pack

Siemens base stations check for a minimum voltage threshold before initiating the charge cycle. A new Ni-MH battery that has sat in storage can drop below this threshold — typically under 3.0V — and the base reads it as a fault rather than a dischargeable cell. This is not a defective battery. Placing the handset in the base for 30 minutes, removing it, then reseating it often allows the base to re-detect and begin charging. If the error persists, check that the handset contacts are clean and making full contact with the base cradle pins.

Range drops noticeably when the battery is below half charge

DECT handsets like the Siemens 240 regulate transmit power partly based on available voltage. As a Ni-MH cell discharges, its terminal voltage sags — and below roughly 3.3V under RF load, the handset reduces transmission power to stay within its operating envelope. This shows up as shortened range or increased call drop rate, not a flat dead battery. The fix is straightforward: return the handset to the base more frequently. After 3–5 full charge cycles, the cell reaches its rated 1200mAh capacity and the voltage sag during RF transmission becomes less pronounced.