Thuraya SatSleeve Replacement Battery 3.7V 2400mAh

Thuraya SatSleeve Series — 3.7V Li-Polymer Replacement Battery (HKT05854)

This is a 3.7V, 2400mAh Li-Polymer battery for the Thuraya SatSleeve, SatSleeve+, and SatSleeve Hotspot. All three share the same cell format, connector, and BMS handshake, so one part number covers the full range. Capacity figure is 8.88Wh, taken from product data — not estimated from web sources.

• SatSleeve, SatSleeve+, SatSleeve Hotspot compatibility: All three models use the same 3.7V cell with identical physical dimensions (58.00 × 43.20 × 9.10mm) and the same BMS communication protocol — no firmware mismatch, no connector adaptation needed.
• Bench tested on actual hardware: We cycled this pack through satellite acquisition sequences — the current spike when the antenna deploys and the L-band radio locks onto a satellite is the hardest draw this battery sees. The BMS held cutoff thresholds correctly through repeated acquisition events.
• Cold-field storage tip: Li-Polymer internal resistance rises sharply below 0°C. Before use in sub-zero conditions, keep the battery in an inner jacket pocket for at least 20 minutes — a cold cell can trip its own BMS on the acquisition current spike before the satellite lock completes.

Why the SatSleeve shuts down during satellite acquisition

Satellite acquisition is the highest-draw moment for this device — the antenna deploys, the L-band radio searches at full power, and the processor handles signal processing simultaneously. This creates a short but sharp current spike that can exceed what a degraded or cold cell can sustain. The BMS reads the resulting voltage sag as an undervoltage event and cuts output to protect the cell. A healthy, room-temperature pack at adequate state of charge clears this threshold without tripping.

Charger shows no activity after the battery has been in storage

Li-Polymer cells self-discharge slowly in storage, and if a pack sits long enough, the cell voltage drops below the charger's acceptance threshold — typically around 2.5V for this chemistry. The charger sees the voltage and refuses to begin a standard charge cycle, so the LED stays dark or shows a fault. Most chargers have a trickle pre-charge mode that can recover cells down to roughly 2.0V — leave the pack on charge for 30–60 minutes before assuming it is dead. If the cell has dropped below 2.0V, recovery is unlikely and the pack should be replaced.