Uniwell CX3500 POS Backup Compatible Battery 7.4V 2600mAh

Uniwell CX3500 — 7.4V Li-Polymer Replacement Battery (YT784262-2S)

This 7.4V, 2600mAh Li-Polymer battery replaces the YT784262-2S backup cell in the Uniwell CX3500 cash register. The CX3500 uses this battery to hold volatile RAM data — including programmed prices, PLUs, and tax tables — during mains power loss. Without a functional backup battery, a power cut can wipe the register's entire configuration.

• CX3500 compatibility: The CX3500's backup circuit expects a 7.4V two-cell Li-Polymer pack with the YT784262-2S pinout. The BMS communicates charge state back to the register's trickle charger — a mismatched pack will either fail to charge or trigger a protection cutoff before the register sees full capacity.
• Bench tested on actual hardware: We cycled this pack through the CX3500's trickle charge circuit and confirmed the BMS accepted charge correctly, held voltage under the register's RAM-sustain load, and released cleanly on mains restore without a reset fault.
• First-install charge requirement: After fitting this battery, leave the CX3500 running on mains power for a full 12 hours before testing backup function. The register charges this pack through a low-current trickle circuit — skipping this step means the battery will not hold enough charge to sustain RAM through even a brief outage.

Why the CX3500 loses programmed prices after a power outage

The CX3500 stores PLUs, price lookups, and tax tables in volatile RAM — not flash. That RAM requires a constant voltage supply to retain data. The backup battery's only job is to hold that rail up the moment mains drops. If the battery voltage has sagged below the RAM sustain threshold — typically around 6.8V under load for a 7.4V pack — data loss happens in seconds. A depleted or degraded original battery is almost always the cause. Fit the replacement, complete the 12-hour trickle charge, and reprogram any lost data before testing.

CX3500 display goes blank the moment mains power fails

The display going blank on mains loss is a different failure from data loss — it means the backup battery cannot sustain the full system load, not just RAM. The CX3500's display and printer draw significantly more current than the RAM-only standby load. If the battery has degraded or was never fully charged, voltage collapses under this combined draw and the register shuts down completely. Charge the replacement pack for 12 hours on mains before testing, then simulate a mains cut — if the display stays live and the printer is idle, the battery is sustaining load correctly.