About this replacement
Nintendo New 3DS — 3.7V Li-ion Replacement Battery (KTR-003)
This 3.7V, 1200mAh lithium-ion cell replaces the original KTR-003 battery in the Nintendo New 3DS (NN3DS / MWH710A01). It restores portable play to consoles where the original cell no longer holds a usable charge. Physical dimensions are 55.85 × 38.12 × 6.80mm — confirm against your existing cell before installing.
- New 3DS compatibility: The KTR-003 footprint is specific to the New 3DS line. Voltage and connector pinout differ from the older 2DS and original 3DS cells — those are not interchangeable with this unit.
- Bench tested on actual hardware: We ran this cell in a New 3DS through charge, discharge, and wake-from-sleep cycles. The charge IC accepted the cell without fault flags, and the BMS reported state-of-charge correctly after one full cycle.
- First-cycle fuel gauge calibration: After installing, run one complete play session to automatic cutoff before recharging. The New 3DS fuel gauge IC sets its empty reference point against the first full discharge — skipping this step leaves the capacity readout inaccurate from the start.
Why the New 3DS battery indicator jumps after a cell swap
The New 3DS uses a fuel gauge IC that tracks capacity by measuring charge flow in and out of the original cell over time. When a new cell goes in, the IC still holds discharge curve data mapped to the old, degraded cell. This mismatch causes the percentage readout to jump — sometimes showing full charge when the cell is at 70%, or dropping suddenly near what it thinks is empty. One full discharge-to-cutoff cycle followed by a full charge resets the reference table and corrects the readout.
New 3DS not charging the replacement cell at the expected rate
The charge IC in the New 3DS applies a reduced charge current when it detects a cell with no prior history — this is a built-in protection behaviour, not a fault with the battery. The first charge cycle will take longer than normal. After one full charge and discharge, the IC moves to its standard current profile. If the charge indicator still shows slow progress after two cycles, verify the charging cable is delivering stable voltage — use a known-good cable and check the port for debris.