About this replacement
Logitech Harmony Touch / Ultimate Series — 3.7V Li-ion Replacement Battery (533-000084)
This is a 3.7V, 1050mAh Li-ion battery for the Logitech Harmony Touch and Harmony Ultimate series remotes, including the Harmony Ultimate One (915-000198). It replaces OEM part numbers 533-000084, 533-000083, and 1209. When the original cell depletes, this swap restores full remote function without replacing the entire unit.
- Harmony Touch, Ultimate, and Ultimate One compatibility: These models share the same battery bay dimensions, connector orientation, and 3.7V supply rail. The same cell fits all three without modification.
- Bench tested on actual hardware: We ran this cell in a Harmony Touch and verified that the onboard BMS accepted the charge cycle, held the cutoff voltage correctly, and powered the touchscreen and IR emitter through full operating range.
- Touchscreen power threshold: The Harmony Touch runs a capacitive touchscreen alongside its IR emitter — both drawing from the same cell. If the remote powers on but the screen is unresponsive, check that the connector tab is fully seated. A partially connected cell drops below the voltage the screen controller needs before the IR circuit shows any symptom.
Why the Harmony Touch shows a charging indicator but the battery never fills
The Harmony Touch charges through a micro-USB port feeding a small internal charge controller. If the original cell has discharged below roughly 2.5V, that controller may not recognise the battery as valid and will cycle on and off without delivering a full charge. A new cell starts above this threshold, so the charge controller accepts it immediately. If the charge indicator still loops after install, seat the connector firmly — the contact pins on this remote are shallow and a loose fit interrupts the charge path.
Remote stops responding mid-session even though the battery shows as charged
An aged Li-ion cell can report adequate voltage at rest but sag sharply the moment the IR LEDs fire a burst command. The Harmony Touch sends multi-device command strings that trigger several IR pulses in quick succession, which pulls more current than a single-button press. If the cell's internal resistance has risen, voltage drops below the processor's minimum during that burst and the remote resets or drops the command. A fresh cell at 3.7V nominal holds steady through those multi-device bursts. If the issue returns quickly on a new battery, check whether a stuck or jammed button is creating a parasitic draw that drains the cell between uses.