GreatCall Jitterbug Plus Replacement Battery 3.7V 800mAh

GreatCall Jitterbug Plus — 3.7V Li-ion Replacement Battery

This 3.7V, 800mAh lithium-ion cell replaces the original battery in the GreatCall Jitterbug Plus mobile phone. It fits the simplified senior-focused handset and restores power to devices where the original cell no longer holds charge. Dimensions are 49.50 x 33.80 x 4.70mm — verify against your existing cell before installation.

• Jitterbug Plus fit: The Jitterbug Plus runs a low-complexity interface but the display backlight and emergency call feature draw steady current from a single cell. This replacement matches the original 3.7V rail and connector orientation so the phone's charge IC recognises the new cell without modification.
• Bench tested on actual hardware: We cycled this cell through a full discharge and charge sequence on the Jitterbug Plus platform. The BMS accepted the cell on the first connection, charge current ramped normally through CC/CV stages, and the phone reached full charge without thermal events.
• Fuel gauge recalibration after swap: After fitting this cell, run one complete discharge down to auto-shutoff, then charge uninterrupted to 100% before normal use. The Jitterbug Plus fuel gauge IC calibrates its coulomb counter against a full discharge curve — skipping this step causes the percentage readout to drift against the new cell's actual capacity.

Why the Jitterbug Plus reports wrong battery percentage after a cell swap

The fuel gauge IC stores a discharge curve from the original cell. When a new cell goes in, the IC is still mapping voltage to percentage against that old curve. The two curves rarely match exactly, so the displayed percentage drifts — sometimes reading 50% when the cell is near cutoff voltage. One full discharge-charge cycle forces the IC to relearn the curve against the new cell. After that cycle, percentage readouts stabilise at the correct values.

Sudden shutdown at 20–30% on the replacement cell

This happens when the cell voltage drops sharply under load from the screen or emergency-call radio module — a voltage cliff the fuel gauge did not predict. The phone hits the low-voltage cutoff and shuts down even though the percentage display showed charge remaining. The fix is completing the recalibration cycle first: drain the phone to auto-shutoff, then charge fully to 100%. After recalibration, the fuel gauge tracks the actual discharge curve and triggers the warning at the correct remaining voltage rather than cutting out at 3.4V without notice.