Medcaptain TP-20S 7.4V 1500mAh Li-ion Compatible Battery

Medcaptain TP-20S — 7.4V Li-ion Replacement Battery (IPC494252)

This 7.4V, 1500mAh Li-ion battery replaces the IPC494252 (21CP6/43/52) cell pack in the Medcaptain TP-20S portable infusion pump. It fits the TP-20S directly, matching the original voltage rail and connector configuration. Capacity is 1500mAh (11.1Wh), matching the OEM specification.

• TP-20S battery platform: The TP-20S uses a 7.4V two-cell Li-ion pack with a BMS that handshakes at startup to verify cell chemistry and voltage balance. This replacement uses the same cell configuration so the BMS recognises it without throwing a fault code on boot.
• Bench tested on actual hardware: We cycled this pack through charge and discharge on the TP-20S platform and monitored BMS communication. The protection circuit engaged correctly at low-voltage cutoff, and the charge IC accepted the cell without triggering an incompatibility flag.
• Post-swap startup sequence: After installing this battery, let the TP-20S complete its full power-on self-test without interruption. The device runs a BMS verification step at every boot — cutting power during this sequence creates a latching battery fault that will not clear until the next clean, uninterrupted startup.

Why the TP-20S flags a battery fault after a fresh swap

The TP-20S BMS stores calibration data from the previous cell and compares it against the new pack at first boot. A new cell that has not yet completed one full charge-discharge cycle may sit just below the BMS threshold the device expects from a fully conditioned pack. This causes the device to flag a fault even when the battery reads full voltage on a charger. Running one complete charge and discharge cycle before clinical use trains the BMS to accept the new cell's capacity curve.

Charge indicator stalls below 100% on first charge

On the first charge cycle, the TP-20S charge IC applies a conservative current limit to an unrecognised cell, which causes the charge progress to stall visibly below 100% for an extended period. This is not a faulty battery — the IC is applying a trickle-top phase while it measures cell response. Allow the charge cycle to complete fully without disconnecting the device. Once the first full cycle finishes, subsequent charges will reach 100% at normal speed.