Turn amp-hour or milliamp-hour readings into a clear remaining capacity percentage. Built for technicians, fleet operators, and storage engineers who need defensible SoC numbers before dispatch or maintenance.
Benefits
- Expresses leftover energy as a percentage: (remaining charge ÷ rated capacity) × 100—aligned with how BMS dashboards and warranty logs report state of charge.
- Works with any chemistry when you know present and full capacity in the same unit—ideal for cross-checking shunt readings, coulomb counters, or bench tests.
- Flags over-capacity inputs so QA teams catch unit mix-ups before they reach commissioning reports or customer handoffs.
How it works
- Measure or estimate the remaining charge stored in the pack (mAh or Ah).
- Enter the manufacturer-rated full capacity in the same unit.
- The tool returns remaining capacity percentage to one decimal place, with ratio detail for your audit trail.
FAQ
What is remaining battery capacity percentage?
It is the fraction of rated capacity still available, expressed as a percent. If a 100 Ah pack holds 72 Ah, remaining capacity is 72%. This is equivalent to state-of-charge (SoC) when rated capacity matches the nameplate value.
How is this different from a voltage-based SoC estimate?
Capacity-percent methods use charge quantities (Ah/mAh). Voltage curves infer SoC from open-circuit voltage and temperature. Use capacity percentage when you have trusted coulomb data; use voltage guides when the pack has been at rest and OEM OCV tables are available.
Should I derate capacity for aged cells?
Yes for accurate remaining energy. Replace the rated capacity input with your aged capacity estimate (e.g., after cycle-life testing) so the percentage reflects usable charge versus present pack capability, not the original datasheet figure.
Technical specifications
- Formula: remaining capacity (%) = (Q_remaining ÷ Q_rated) × 100; clamped 0–100%.
- Inputs: positive numeric values; Q_remaining and Q_rated must share the same unit (mAh or Ah).
- Output: percentage to ±0.1%, capacity ratio detail string, over-capacity advisory when Q_remaining > Q_rated.
- Reference: pairs with IEC 62619 pack documentation and field coulomb-counting validation workflows.
Remaining charge vs. rated nameplate
Remaining capacity percentage answers a simple question: how much of the rated bucket is still full? It does not, by itself, account for temperature, Peukert effect, or internal resistance—pair results with load tests when sizing runtime-critical applications.
When to recalculate after partial cycles
After shallow cycles, remaining percentage from coulomb counting tracks well. After long storage or deep discharge, verify against a full charge/discharge benchmark or BMS calibration routine so drift does not accumulate in fleet logs.