Yoto YP004 Replacement Battery 3.7V 5000mAh Li-ion

Yoto YP004 Player 3rd Gen — 3.7V Li-ion Replacement Battery (INR21700)

This is a 3.7V, 5000mAh (18.5Wh) Li-ion INR21700 cell for the Yoto YP004 and Player 3rd Gen children's audio device. It replaces the original cell when the player no longer holds a charge or shuts down during playback. Dimensions are 73.70 × 22.00 × 22.00mm — confirm these against your existing cell before ordering.

• YP004 and Player 3rd Gen compatibility: Both devices share the same INR21700 cell format, 3.7V nominal voltage rail, and physical bay dimensions. The BMS inside the player communicates directly with this cell chemistry, so no firmware or handshake issues arise on swap.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the YP004 platform. The BMS accepted the cell without triggering protection cutoffs, and the fuel gauge tracked accurately from full to low-battery warning.
• Fuel gauge reset after replacement: After fitting a new cell, run the player down past the low-battery indicator and then charge to 100% in a single uninterrupted session. This recalibrates the fuel gauge — skipping this step causes the indicator to report inaccurate charge levels for weeks.

Why the YP004 reads full charge but audio cuts after extended play

This happens when the fuel gauge has drifted from shallow-cycle use — the player being topped off repeatedly without ever reaching a full discharge. The BMS loses its reference for true empty, so the reported state of charge runs ahead of actual cell capacity. The player cuts out when the cell hits the BMS low-voltage threshold, even though the screen still shows significant charge. A full discharge-to-charge cycle resets the gauge reference and corrects the reading.

USB-C not waking the YP004 after the battery went completely flat

When the cell drops below approximately 2.5V, the BMS enters deep-discharge lockout and the USB-C port stops responding to standard chargers. The charger handshake expects the cell to be above the minimum PD acceptance voltage before negotiating power delivery. To recover, leave the cable connected for 10–15 minutes — most chargers will trickle a small pre-charge current that brings the cell up to the 2.8–3.0V threshold, at which point the BMS re-enables normal charging.