Off-Grid Battery Bank Sizing (Solar)

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

t4-174

Ledger rows

1

No ledger note is attached.

Review findings

The Ah equation is standard under its stated assumptions, but the unspecified efficiency definition and missing kWh formula prevent an unqualified PASS. The existing design-estimate label is appropriate; the instrument should also disclose that it is not a complete professional battery, inverter, conductor, protection, temperature, aging, or energy-harvesting design.

Formula and scope findings

• The Ah formula is conditionally standard: Ah = daily_load_Wh × autonomy_days ÷ (DoD × Vsystem × efficiency), assuming efficiency represents the total loss factor between nominal battery energy and delivered load energy. The efficiency definition and measurement point are unspecified.
• The declared kWh output has no formula. If it means nominal battery-bank energy, the required formula is bank_kWh = required_Ah × Vsystem ÷ 1000. If it means usable or load-delivered energy, it will have a different value and must be labeled accordingly.
• The formula does not specify whether daily load is measured at the AC loads, DC loads, inverter input, or battery terminals; this changes whether inverter and wiring losses belong in efficiency.

Unit assumptions

• daily_load_Wh is energy consumed per day in watt-hours, not load power in watts.
• autonomy_days is in days.
• DoD is a decimal fraction, such as 0.8 for 80%, not the integer 80.
• Vsystem is volts and is consistent with the battery-bank nominal voltage.
• efficiency is a dimensionless decimal fraction, such as 0.9 for 90%, and is greater than zero.
• The reported bank_kWh in these vectors means nominal bank energy before DoD and efficiency losses: required_Ah × Vsystem ÷ 1000.

Boundary hardening

BREAK_CLAIMED · SELF_FLAGGED

The formula is undefined when depth of discharge is zero, and the specification does not state required input validation. It also has no actual formula branches and leaves negative-load convention and efficiency range behavior ambiguous.

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": {
    "daily_load_Wh": 3000,
    "autonomy_days": 2,
    "DoD": 0.8,
    "system_V": 48,
    "efficiency": 0.9
  },
  "expected_outputs": {
    "required_bank_Ah": 173.6111111111,
    "bank_kWh": 8.3333333333
  },
  "working": "Daily autonomy energy = 3000 Wh/day × 2 days = 6000 Wh. Denominator = 0.8 × 48 V × 0.9 = 34.56. Required Ah = 6000 ÷ 34.56 = 173.6111111111 Ah. Nominal bank energy = 173.6111111111 Ah × 48 V ÷ 1000 = 8.3333333333 kWh."
}

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