Sanyo DY002 Replacement Battery 3.7V 600mAh Li-ion

Sanyo DY002 — 3.7V Li-ion Replacement Battery (TY02)

This is a 3.7V, 600mAh Li-ion cell for the Sanyo DY002 portable media player. It replaces OEM part TY02 directly. If your DY002 no longer holds a charge or won't power on after sitting unused, this is the battery that fits it.

• DY002 fit: The DY002 runs a single-cell 3.7V Li-ion configuration. Voltage, connector pinout, and BMS handshake all match the original TY02 spec. No modification needed.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a Li-ion analyzer. The BMS tripped correctly at low-voltage cutoff and accepted a full charge without thermal event or cell imbalance.
• Post-swap charge cycle: After fitting a new cell, connect the DY002 to its charger before attempting to power it on. A deeply discharged or long-stored cell can sit below the BMS activation threshold — the player needs a slow trickle input first to bring the cell voltage up enough for the protection circuit to release.

Battery percentage jumping after cell swap in the DY002

The DY002 estimates remaining charge using voltage thresholds calibrated to the original cell's discharge curve. A new cell has a slightly different internal resistance profile, so the indicator can jump — showing 80%, then 60%, then 95% within minutes. This settles after two or three full charge-discharge cycles as the player re-maps the curve. Don't judge capacity from the first cycle's readout.

Playback cutting out before the battery indicator shows empty

The audio amplifier in the DY002 is the highest-draw component on the board. As the cell approaches the bottom of its discharge curve, voltage sags under load faster than the indicator updates. The player's protection circuit then cuts power to prevent over-discharge — even if the display still shows one bar remaining. If this happens consistently, charge the unit back to full and check that the charge port isn't intermittent. A confirmed full charge should bring terminal voltage to 4.2V.