SteelSeries Nimbus Controller Compatible Battery 3.7V 750mAh

SteelSeries Nimbus / Stratus Duo / Nimbus+ — 3.7V Li-Polymer Replacement Battery (FT712257P)

This is a 3.7V, 750mAh lithium-polymer replacement battery for the SteelSeries Nimbus Controller, Stratus Duo, and Nimbus+. All three are wireless game controllers used with iOS, tvOS, and Mac devices. The FT712257P cell fits the shared internal battery slot across this controller family.

• Nimbus / Stratus Duo / Nimbus+ compatibility: These three controllers share the same PCB layout, battery connector, and BMS handshake protocol. The FT712257P format — 51.50 × 20.00 × 7.00mm — fits all three bays without modification.
• Bench tested on actual hardware: We cycled this cell on a Nimbus controller under active wireless pairing and button polling load. The BMS held a stable charge curve through cutoff and accepted a full recharge from flat without tripping protection.
• Fuel gauge conditioning after install: On first use, run one complete wireless play session to full automatic cutoff before recharging. The Nimbus fuel gauge IC sets its empty reference point against the first full discharge cycle — skipping this step causes the indicator to read inaccurately for weeks.

Nimbus controller disconnecting before the battery indicator reaches empty

The Nimbus wireless stack and any active rumble motor draw current simultaneously. Under that combined load, a degraded or new unconditioned cell sees a voltage sag that briefly pulls the supply rail below the BMS disconnect threshold. The controller reads this as a fault and drops the Bluetooth link — even though the indicator still shows charge remaining. This is not a firmware bug. After 3–5 full conditioning cycles, internal resistance drops and the sag narrows. If disconnects persist past five cycles, check that the battery connector is fully seated, as a loose contact amplifies the sag under load.

Fuel gauge jumping or freezing on the Nimbus after a cell swap

The Nimbus uses a coulomb-counting fuel gauge IC that tracks charge and discharge against a stored discharge curve from the original cell. A new cell has a different internal resistance profile, so the IC's model no longer matches actual capacity. You'll see the indicator jump — typically from full to half — or freeze at one level for an extended period. This resolves itself after the IC re-learns the new cell's curve across 3–5 full cycles. Do not judge the replacement battery's condition until at least three full discharge-recharge cycles are complete; the gauge reading before that point is not reliable.