Source: https://guthlabs.ai/docs/instruments/battery-pack-series-parallel-configurator/
instrument / verified-clean
# Battery Pack Series/Parallel Configurator
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**: t4-126
**Ledger rows**: 1
No ledger note is attached.
## Review findings
The core series/parallel arithmetic is standard and correct under the stated ideal assumptions. The specification needs an explicit voltage convention (nominal, maximum, or operating range), explicit validation constraints for S and P, and either removal of the optional weight output or a defined weight formula and required inputs.
### Formula and scope findings
- Vpack=S·Vcell, Cpack=P·Ccell, and Wh=Vpack·Cpack are correct for identical cells in an ideal SxP arrangement.
- The formulas do not account for voltage sag, usable-depth-of-discharge limits, charge/discharge efficiency, cell mismatch, wiring losses, or BMS limits; outputs are therefore nominal/theoretical values.
- The listed optional weight estimate has no formula, cell-mass input, enclosure-mass input, or definition of whether it is an estimate or a measured result.
### Unit assumptions
- Vcell is in volts (V), Ccell is in ampere-hours (Ah), and Wh is watt-hours.
- Vcell and Ccell are nominal cell ratings; Wh is nominal stored energy, not guaranteed usable energy.
- S and P are positive integer counts: S is the number of cells in series and P is the number of parallel strings.
- Cells in every series and parallel position are assumed identical and connected in a conventional SxP topology.
- If capacity is supplied in mAh, it must be divided by 1000 before applying Cpack=P·Ccell; for example, 2500 mAh=2.5 Ah.
- The spec does not explicitly state nominal versus maximum/minimum cell voltage, so the voltage interpretation is ambiguous.
## Boundary hardening
### Recorded hazards
- Reject S<=0 or P<=0; zero or negative counts are physically invalid and can produce zero or nonsensical pack ratings.
- Require S and P to be integers; fractional cell counts are invalid.
- Reject missing, nonnumeric, zero, or negative cell voltage and capacity inputs.
- Avoid division by zero in any future reverse-calculation feature when deriving S, P, or cell values.
- Prevent accidental mixing of mAh and Ah; silently treating 2500 mAh as 2500 Ah creates a 1000-fold capacity and energy error.
- A pack's actual usable energy is lower or different than nominal Wh depending on cutoff voltage, load, temperature, aging, and efficiency.
- A weight output without a defined model must not be presented as an authoritative result.
## 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": {
"cell_voltage_V": 3.7,
"cell_capacity_Ah": 2.5,
"S": 3,
"P": 4
},
"expected_outputs": {
"pack_voltage_V": 11.1,
"pack_capacity_Ah": 10,
"pack_energy_Wh": 111
},
"working": "Vpack=S·Vcell=3·3.7=11.1 V. Cpack=P·Ccell=4·2.5=10 Ah. Wh=Vpack·Cpack=11.1·10=111 Wh."
}
````
## Related workflows
[Off-Grid Solar Designerpack build]()
## 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`