CAT B25 Replacement Battery 3.7V 1450mAh Li-ion UP073450AL

CAT B25 — 3.7V Li-ion Replacement Battery (UP073450AL)

This is a 3.7V, 1450mAh Li-ion cell for the CAT B25 rugged mobile phone. It replaces OEM part UP073450AL and fits the B25 body directly. Capacity is 1450mAh (5.37Wh) — matching the original specification.

• CAT B25 fitment: The B25 uses a specific cell footprint — 56.00 x 34.10 x 7.70mm — with a connector and BMS handshake tied to the phone's charge IC. This cell matches that footprint and connector orientation, so the charge circuit recognises it on first insertion.
• Bench tested on actual hardware: We ran this cell through a full charge cycle on the B25 charge IC and confirmed the BMS communicated correctly, charge current ramped as expected, and the phone did not throw a battery fault at any charge state.
• Fuel gauge recalibration after installation: On first use, disable any fast-charge mode and run one complete discharge-charge cycle at standard current. This lets the phone's fuel gauge IC map the new cell's discharge curve before it starts reporting percentages or triggering low-battery cutoffs against stale data from the old cell.

Sudden shutdown at 20–30% on the replacement cell

The B25 fuel gauge IC stores a discharge model calibrated to the old cell. When a new cell goes in, that model is wrong — the IC thinks there is charge remaining when the actual cell voltage is already sagging under load. Screen-on or active call states draw enough current to collapse cell voltage below the BMS cutoff threshold, causing an abrupt shutdown even though the status bar still showed charge. One full discharge-charge cycle at standard current forces the coulomb counter to reset and relearn the new cell's actual capacity. After that cycle, shutdown events at 20–30% stop.

Phone reports wrong battery percentage after cell swap

The CAT B25 uses a fuel gauge IC that tracks capacity via a coulomb counter — it integrates charge and discharge current over time against a stored cell model. Swapping cells does not reset that model automatically, so the IC continues using the old cell's charge curve as reference. This produces percentage readings that jump, stall, or plateau at values that do not reflect actual cell state. Charge the phone to 100% until the charge IC terminates, then drain it fully to automatic shutdown — one complete cycle recalibrates the counter against the new cell and stabilises the percentage display.