Solar Charge Controller Sizing (PWM/MPPT) mechanism

Model scope

The existing honest label is appropriate but should explicitly state that this is not a complete MPPT-window or controller-capacity determination. To pass, define series/parallel aggregation, require cold-corrected Voc from module datasheet temperature coefficients, check both MPPT voltage limits using array Vmp and temperature conditions, and define whether current sizing is PV-input current or regulated battery-output current.

• Icontroller ≥ Isc × 1.25 is a valid NEC-style minimum-current estimate only if Isc is the total array short-circuit current in amperes and the controller rating being checked is the applicable current rating. It does not by itself verify charge-controller output-current sizing from array power and battery voltage.
• Voc_string < controller max Vin checks only the upper voltage limit. It is not a complete MPPT input-voltage-window check because the controller's minimum MPPT voltage and the array's operating Vmp are missing.
• The formula requires Voc_string at the coldest expected temperature, but no cold-temperature correction formula or required datasheet coefficient is provided. A nominal or STC Voc is insufficient for the maximum-voltage check.
• The specification does not define how Isc and Voc are aggregated for series and parallel strings. Isc normally adds across parallel strings, while Voc adds across series-connected modules.
• The strict less-than comparison is conservative at the controller maximum-voltage boundary, but the specification should explicitly state whether manufacturer-required voltage margin is also required.

Units and conventions

• Isc is the total array short-circuit current, expressed in amperes.
• Voc_string and controller max Vin use the same voltage unit, volts, and Voc_string is the cold-corrected maximum open-circuit voltage of the complete series string.
• The 1.25 factor is dimensionless.
• The controller current rating is assumed to be compared directly with the calculated 1.25 × Isc value; actual controller output-current sizing may additionally require array power, battery voltage, and controller efficiency or manufacturer limits.
• A complete MPPT-window check would require controller minimum and maximum MPPT voltages plus array Vmp under relevant temperature conditions.

Inspectable vector

One of 4 source-bound review vectors:

{
  "inputs": {
    "array_Isc_A": 10.8,
    "cold_corrected_string_Voc_V": 41.2,
    "controller_max_input_voltage_V": 60
  },
  "expected_outputs": {
    "required_controller_current_A": 13.5,
    "maximum_voltage_check": "PASS"
  },
  "working": "Required current = Isc × 1.25 = 10.8 A × 1.25 = 10.8 A + (10.8 A × 0.25) = 10.8 A + 2.7 A = 13.5 A. Voltage check: 41.2 V < 60 V, so PASS."
}

Failure boundary

BREAK_CLAIMED · SELF_FLAGGED

An extreme but numerically valid Isc input produces Infinity in JavaScript arithmetic, and a negative signed Isc can produce an invalid negative required rating unless the instrument explicitly applies a magnitude convention. Exact voltage equality also correctly fails because the specified comparison is strict.

Other records

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json
• evidence-tranche4/tranche4-results.json
• BOUNDARY_HAZARD_CATALOG.json