About this replacement
Samsung YP-K5 / YP-K5J — 3.7V Li-Polymer Replacement Battery (503040)
This is a 3.7V, 600mAh lithium-polymer replacement battery for the Samsung YP-K5 and YP-K5J portable media players. Part number 503040. It fits the compact form factor of both units and matches the original connector and cell dimensions (40.02 × 29.26 × 4.50mm).
- YP-K5 and YP-K5J compatibility: Both models share the same battery bay dimensions, connector pinout, and 3.7V power rail. The cell is a flat lithium-polymer pouch — not a cylindrical cell — so the physical fit and BMS voltage thresholds are identical across both variants.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on a YP-K5 unit. The BMS accepted the cell without flagging a fault, and the device registered a full charge state at 4.2V. No protection-circuit tripping occurred during normal playback draw.
- Post-swap charging on the YP-K5: After fitting this cell, connect the player to a charger before attempting to power it on. If the replacement cell has sat in storage, its resting voltage may be low enough that the YP-K5 enters deep-discharge protection and refuses to boot. A slow trickle from the charger for 20–30 minutes resolves this before you apply full charge current.
Battery percentage jumping on the YP-K5 after a cell swap
The YP-K5 uses a voltage-threshold method to estimate battery level — it does not count charge cycles. After fitting a new cell, the player's indicator may jump between values or show a full bar then drop suddenly. This happens because the internal reference points were calibrated to the wear curve of the old cell. Run the player down to auto-shutoff, then charge it uninterrupted to 4.2V. One full cycle re-anchors the voltage thresholds and the indicator stabilises.
Playback cutting out before the battery indicator shows empty
The audio amplifier in the YP-K5 draws a brief current spike when driving headphone output at higher volumes. Near the end of discharge — typically below 3.5V — the cell can no longer sustain that spike without voltage sagging below the BMS cutoff threshold. The device shuts off even though the indicator still shows one bar. This is a cell-voltage floor issue, not a firmware fault. Keeping playback volume below 80% extends usable discharge depth on an aging or newly fitted cell.