Solar Charge Controller Sizing (PWM/MPPT)

Inspectable records

Ledger state

The current ledger marks this instrument verified clean within the source-bound verification corpus.

Area

Electrical & Electronics Engineering — Circuits, Power Systems, Electronics Lab

Tranche

tranche-4

Evidence ID

t4-162

Ledger rows

1

No ledger note is attached.

Review findings

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.

Formula and scope findings

• 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.

Unit assumptions

• 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.

Boundary hardening

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.

Errata and corrections

No applied erratum is attached to this unique-name record.

Inspectable example

4 review vectors are recorded. One source-bound sample is shown below.

{
  "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."
}

Related workflows

Sources and evidence

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

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