Nintendo DSi Replacement Battery TWL-003 3.7V 550mAh

Nintendo DSi / NDSiL — 3.7V Li-Polymer Replacement Battery (TWL-003)

This is a 3.7V, 550mAh Li-Polymer replacement cell for the Nintendo DSi, NDSi, and NDSiL handheld consoles. It fits the original battery slot and connects via the factory connector without modification. OEM part numbers TWL-003 and C/TWL-A-BP both cross to this cell.

• DSi, NDSi, and NDSiL compatibility: All three models share the same battery bay dimensions, voltage rail, and connector pinout. The DSi's charge IC expects a 3.7V nominal Li-Polymer cell — this replacement matches that spec exactly, so the charge circuit behaves normally from the first session.
• Bench tested on actual hardware: We seated this cell in a DSi unit and cycled it through the console's onboard charge IC. The BMS accepted charge without flagging a fault, voltage at full charge measured 4.19V, and the fuel gauge updated correctly across the discharge curve.
• Fuel gauge calibration on first install: The DSi reads cell state by tracking coulombs from a known reference point. After swapping cells, run one complete play session to automatic shutoff before recharging — this lets the console's fuel gauge IC lock onto the new cell's actual empty voltage and recalibrate its capacity estimate accurately.

DSi battery indicator jumping or showing wrong charge level after a cell swap

The DSi uses a simple coulomb-counting fuel gauge that references discharge data from the previous cell. When a new cell goes in, the IC has no baseline, so it interpolates — badly. The indicator can jump from three bars to one, or show full charge and then cut off unexpectedly. One complete discharge to automatic shutoff followed by a full charge resets the reference. After that cycle, the gauge tracks accurately against the new cell's actual 3.7V nominal curve.

New DSi battery lasting noticeably less than the original at first

Fresh Li-Polymer cells ship with partial formation cycles — the electrolyte hasn't fully wetted all active material yet. On the first one to three cycles, usable capacity sits below the rated 550mAh. This is normal cell chemistry, not a fault. Capacity builds toward the rated figure over three to five full charge-discharge cycles. If capacity hasn't improved by cycle five, check that the battery contacts are clean and seating flush against the console's spring terminals.