Olympus mrobe MR-100 Compatible Battery 3.7V 750mAh

Olympus mrobe MR-100 — 3.7V Li-ion Replacement Battery (ZT005032)

This is a 3.7V, 750mAh Li-ion battery for the Olympus mrobe MR-100 portable media player. It replaces OEM part number ZT005032. The mrobe MR-100 is a touchscreen audio and video player from the mid-2000s, and this cell fits the original battery bay with no modification.

• mrobe MR-100 fit: The MR-100 uses a compact single-cell Li-ion pack at 3.7V nominal. The ZT005032 form factor — 34.00 × 38.30 × 5.30mm — matches the original bay dimensions. The BMS communicates charge state directly to the device firmware, so the battery indicator reads correctly after calibration.
• Bench tested on actual hardware: We ran full charge and discharge cycles on the MR-100 platform. The BMS triggered protection cutoff at the expected low-voltage threshold without locking the device into an unrecoverable state. Charge acceptance from the stock USB cradle was normal throughout.
• First-charge after a cell swap: After installing this battery, charge it fully before first use. Media players like the MR-100 frequently enter deep discharge protection after extended storage. The device may not respond to the power button until a slow trickle charge brings the cell voltage above the BMS wake threshold — typically around 3.0V.

Battery percentage jumping after cell swap on the MR-100

The MR-100 estimates charge level by reading cell voltage against a fixed lookup table stored in firmware. After swapping to a new cell, the firmware's stored reference points no longer match actual cell behaviour. This causes the indicator to jump — showing 80%, then 40%, then back up — during the first few cycles. Run two or three full charge-to-discharge cycles and the voltage curve stabilises. After that, the percentage display tracks accurately.

Playback cutting out before the battery indicator shows empty

The MR-100's audio amplifier draws a brief current spike when it drives the output stage, especially at higher volume levels. At the tail end of a discharge cycle, cell voltage sags under that load and briefly dips below the BMS cutoff threshold — even though the indicator still shows charge remaining. The device cuts out not because the battery is dead, but because instantaneous voltage dropped too low. Plugging into the charger and restarting will confirm remaining capacity; if the device powers on immediately, the cell had charge left but couldn't sustain the load spike.