Source: https://guthlabs.ai/docs/instruments/battery-capacity-c-rate-runtime-calculator/
instrument / verified-clean
# Battery Capacity / C-Rate / Runtime Calculator
The current ledger marks this instrument verified clean within the source-bound verification corpus.
Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**
## Inspectable records
[01**Overview**Purpose and lifecycle]()[02**Mechanism**Method and assumptions]()[03**Implementation**Binding and validation]()[04**Qualification**Evidence and errata]()
## 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**: t4-114
**Ledger rows**: 1
No ledger note is attached.
## Review findings
The two stated arithmetic formulas are valid only under the Ah/A ideal-battery assumptions. The specification is incomplete because it advertises Ah/Wh capacity, current/power load, and derated capacity without defining the required Wh/W formula, voltage conversion, derating model, or constraints.
### Formula and scope findings
- t = Capacity(Ah) / I(A) is correct for an ideal battery when capacity is in ampere-hours and load is a constant current in amperes.
- I_max = C-rate × Capacity(Ah) is correct for nominal maximum discharge current when C-rate is dimensionless and capacity is in ampere-hours.
- The declared capacity input may be Ah or Wh, but the runtime formula only supports Ah; Wh requires t = Energy(Wh) / Power(W), or conversion using nominal voltage.
- The declared load input may be current or power, but no voltage input or power-based runtime formula is provided for power loads.
- The declared output derated capacity has no formula or defined inputs; it cannot be computed from the supplied formulas.
- The exact ambiguity requiring review is whether runtime inputs are capacity/current in Ah/A or energy/power in Wh/W, and how nominal voltage should be supplied for conversion between them.
### Unit assumptions
- Capacity is in Ah for the supplied runtime and C-rate formulas.
- Load is a constant current in A; runtime is returned in hours.
- C-rate is dimensionless, expressed as a multiple of the rated capacity per hour; for example, 1C × 100Ah = 100A.
- For Wh/W operation, runtime would be in hours only after using t = Wh/W; converting power to current requires voltage in volts.
- The formulas are ideal estimates and do not include Peukert behavior, voltage sag, cutoff voltage, temperature, aging, or discharge-rate-dependent capacity.
## Boundary hardening
**BREAK_CLAIMED** · SELF_FLAGGED
A zero load current creates a division-by-zero runtime result, and the specification does not define whether to reject it or report unlimited idealized runtime. Negative-current sign handling is also unspecified, producing either a misleading negative runtime or a charging-state interpretation. No derated-capacity formula or true piecewise branch is supplied.
## 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": {
"capacity_Ah": 100,
"load_current_A": 5,
"c_rate": 0.5
},
"expected_outputs": {
"runtime_hours": 20,
"max_discharge_current_A": 50
},
"working": "Runtime: t = Capacity / current = 100 Ah / 5 A = 20 h. Maximum current: I_max = C-rate × Capacity = 0.5 × 100 Ah = 50 A."
}
````
## Related workflows
[Off-Grid Solar Designerruntime check]()
## 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`