Telekom Speedphone 300 Replacement Battery 3.7V 650mAh

Telekom Speedphone 300 — 3.7V Li-ion Replacement Battery

This is a 3.7V, 650mAh Li-ion replacement battery for the Telekom Speedphone 300 DECT cordless handset. It fits directly into the handset's battery compartment and restores normal wireless calling operation. Capacity is 2.41Wh, matching the original cell specification.

• Speedphone 300 fit: The Speedphone 300 uses a slim single-cell Li-ion pack at 3.7V nominal. The cell dimensions — 47.00 x 34.00 x 4.60mm — match the original bay exactly, so the connector seats without modification and the handset's charge circuit reads the pack correctly.
• Bench tested on actual hardware: We cycled this pack through the Speedphone 300's charge circuit and confirmed the BMS accepted a full charge without flagging a fault. The cell held voltage within expected range across standby and active RF transmission.
• First charge after installation: Place the handset in its base cradle immediately after fitting this battery and leave it for a full 16 hours before use. Li-ion cells shipped in partial-charge storage states need a complete slow charge through the handset's own circuit to reach rated capacity accurately.

Talk time shorter than the original battery after replacement

A Li-ion cell shipped from storage arrives at roughly 40–60% state of charge. The handset's charge circuit tops it up, but the cell hasn't been cycled yet. Capacity readings settle after three to five full charge and discharge cycles as the cell's internal resistance stabilises. If talk time is still noticeably short after five cycles, check the handset contacts and base cradle pins for oxidation — a high-resistance connection limits charge current and the cell never reaches 4.2V full charge.

Base station showing no charge or error light after battery swap

Some DECT base stations check the handset battery voltage before initiating the charge cycle. A cell that has dropped below roughly 3.0V during storage may sit outside the base's acceptance window, causing it to display an error light or simply not charge. Remove the handset, leave it off the base for 30 seconds, then reseat it firmly so all cradle contacts touch. If the error persists, check that the cradle pins are clean and that the handset battery compartment cover is fully closed — a loose cover can shift the cell slightly off the contacts.