Separating System Load From Battery Charge Termination

A charger can remain in a charging state because the measured current includes a system load as well as battery current. Whether that happens depends on the charger’s power path architecture and the board connections. Review where current is measured before adjusting a termination threshold to make a status indicator change.

Draw the source, system, and battery paths

Identify the input source, system output, battery connection, and any external load sharing components. Mark which current the charger uses for regulation and termination. The TI BQ2407x data sheet describes a power path charger family with separate system and battery connections and device specific charge termination behavior.

Use the actual device’s functional description rather than assuming every charger separates those currents. Connecting the system to a battery pin when the design expects a system output can change the behavior even if the battery still receives current.

Review the termination conditions

List the required voltage region, current threshold, timing conditions, and states that suspend or modify termination. Include input current limiting and thermal regulation where relevant. A low programmed charging current or constrained input source can interact with the termination decision.

Do not alter charging limits outside the battery manufacturer’s requirements to compensate for a wiring or architecture problem. The battery chemistry and approved charging profile remain the controlling design inputs.

Measure currents separately

Observe input, system, and battery currents with an appropriate measurement arrangement. Compare the charging process with the system idle and with representative activity. Check whether the battery current falls as expected while another path continues to supply the running electronics.

As an illustrative situation, a 30 mA system load can exceed a hypothetical 20 mA termination threshold if the architecture measures their combined current. That example explains the mechanism; it is not a recommended threshold for any battery.

Test source removal and load changes

Verify behavior when input power arrives, disappears, or becomes current limited. Observe system voltage and battery current direction during those transitions. Record any temporary battery supplement operation separately from normal charging. A charging test with the system disconnected does not establish the complete product’s behavior.

Save the power path diagram, charger settings, battery requirements, current measurements, and status transitions. Acceptance should show that charging and termination operate correctly while the product performs its intended functions. A full battery icon or a change in the charger status pin is supporting evidence only after the underlying current paths and specified termination conditions have been verified.