SeaLife Sea Dragon 1200 Replacement Battery 7.4V 3000mAh

SeaLife Sea Dragon Series — 7.4V Li-ion Replacement Battery (SL9831)

This is a 7.4V 3000mAh Li-ion replacement for the SeaLife SL9831 battery. It fits the Sea Dragon 1200, 1500, 2000, and 2100SF underwater flashlights, plus additional Sea Dragon variants. These are high-draw diving torches used by underwater photographers who need consistent output at depth.

• Sea Dragon platform compatibility: The Sea Dragon line shares a common 7.4V dual-cell architecture and the same physical pack format across the 1200 through 2100SF models. The BMS pinout and connector are standardised across the range, so one pack covers the full series without modification.
• Bench tested on actual hardware: We ran this pack on the Sea Dragon driver circuit and confirmed the BMS handshake completed correctly on first insertion. The protection circuit tripped at expected low-voltage cutoff, and charge acceptance across both cells was balanced throughout the cycle.
• Multi-cell replacement timing: The Sea Dragon pack houses two cells in series. If you mix a fresh replacement with a partially degraded original cell, the weaker cell depletes first under high-current turbo draw. Replace both cells from the same batch simultaneously — the SL9831 is a paired pack, so this happens automatically when you swap the full unit.

Why the Sea Dragon steps down output before the battery indicator reads low

The Sea Dragon's driver circuit uses brownout protection that monitors cell voltage in real time. As the pack approaches the lower end of its discharge curve, the driver steps output down before the indicator LED changes state. This is intentional — it protects the cells from dropping below safe voltage under the high current that turbo mode pulls. The indicator reflects state-of-charge, not the driver's voltage threshold, so the two can diverge by several minutes of use.

Turbo mode draining the pack significantly faster than standard mode

Turbo mode on the Sea Dragon 1200 draws substantially more current than standard or low modes — the ratio is typically five to ten times higher depending on the driver configuration. At that draw rate, a 3000mAh pack discharges along the steep section of the discharge curve faster than the indicator can track. If turbo runtime feels too short, switch to standard mode for mid-dive use and reserve turbo for targeted shots. Resting cell voltage after a turbo session should read above 6.4V on a multimeter — anything below that indicates the pack was taken close to cutoff.