Source: https://guthlabs.ai/docs/instruments/battery-charge-time-estimator/implementation/

instrument implementation / implementation-contract

# Battery Charge Time Estimator implementation

A source-bound implementation contract for Battery Charge Time Estimator; deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t4-138

**Effect**: Computation or source lookup only

## Input and validation requirements

A zero charging current produces an undefined division-by-zero result, and the CC-CV note describes a second regime without supplying a CV taper formula or data needed to calculate it. Negative-current handling is also unspecified and can produce a nonsensical negative time if applied literally.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "capacity_Ah": 2.4,
    "charge_current_A": 1.5,
    "efficiency_percent": 90
  },
  "expected_outputs": {
    "estimated_charge_time_hours": 1.77777778
  },
  "working": "efficiency_fraction = 90 / 100 = 0.90; base_time = 2.4 Ah / 1.5 A = 1.6 h; estimated_time = 1.6 h × (1 / 0.90) = 1.6 / 0.90 = 1.77777778 h."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/battery-charge-time-estimator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/battery-charge-time-estimator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/battery-charge-time-estimator/qualification/>)

## 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`