About this replacement
Sagem Sagemcom HM40 — 7.2V Ni-MH Replacement Battery (1118)
This 7.2V, 2000mAh Ni-MH battery is a direct replacement for the Sagemcom HM40 portable DAB digital radio. It replaces OEM part number 1118 and restores the radio to full operation when the original cells have degraded. Dimensions are 101.36 × 29.68 × 29.68mm — confirm these against your existing pack before ordering.
- Sagemcom HM40 fitment: The HM40 uses a single proprietary pack at 7.2V to power both the DAB+ decoder and the RF front-end from one source. Voltage and physical dimensions must match exactly — the radio's power management circuit will reject packs outside its expected range.
- Bench tested on actual hardware: We ran this pack through charge and discharge cycles on a DAB radio platform, confirmed the Ni-MH cells held stable voltage across the decoder's operating range, and verified the pack seated and made contact correctly.
- Post-swap station scan: After fitting the new battery, run a full auto-scan before manual tuning. The HM40 stores its station list in volatile memory — any power interruption resets it, and the radio needs a fresh scan to rebuild the complete DAB multiplex list for your area.
DAB radio cutting out mid-station at low battery
The HM40's DAB decoder needs a stable voltage to maintain stream synchronisation. As Ni-MH cells discharge, terminal voltage drops — not gradually, but in a steeper curve near the end of the charge cycle. When voltage sags below the decoder's minimum, the digital stream breaks up or the radio mutes entirely rather than producing distorted audio. Replacing an aged pack that can no longer hold voltage under the decoder's current draw stops this behaviour immediately.
Reception worse than expected after fitting a new battery
DAB radios increase RF output power when searching for weak or marginal multiplex signals — this draws more current than normal playback. If the installed pack is undercharged or the cells haven't been through a full conditioning cycle, terminal voltage sags under the higher RF load and the tuner can't sustain full search power. Allow the battery to complete at least one full charge before judging reception quality. If the issue persists on a weak signal, move the radio to a location with a stronger DAB signal to rule out coverage gaps rather than a battery problem.