Cell Design and Materials

Battery Performance Metrics: Definitions and Applications 2/2 Performance Metric

Definition

Improvements Enable

Coulombic Efficiency

The ratio of charge extracted during discharge to charge supplied during charge in a single cycle.

Understanding long-term capacity fade, lithium inventory loss, and cycle life prediction EV, Grid, R&D.

Depth of Discharge DoD Capability

The allowable fraction of total capacity that can be repeatedly used without accelerated degradation.

Lifetime optimization and usable energy planning Grid storage, EVs).

State of Charge SOC Accuracy

The accuracy with which the batteryʼs remaining charge can be estimated during operation.

Reliable battery management, range prediction, and user confidence EV, Consumer, Medical).

Round-Trip Energy Efficiency:

The ratio of energy delivered during discharge to energy required during charge

Enables applications where energy losses directly impact operating cost and system sizing Grid, EV, Storage)

Usable Energy vs. Temperature:

The fraction of nominal energy that can be delivered as a function of operating temperature

Enables applications requiring predictable runtime across climates EV, Grid, Aerospace, DOD

Usable Power vs. Temperature:

The maximum deliverable power output as a function of temperature without exceeding voltage or Enables cold-start and high-power operation in extreme thermal limits environments EV, eVTOL, Aerospace, Military)

Internal Resistance DCIR / ACIR

The effective resistance of the cell that causes voltage drop and heat generation under load

Enables assessment of power capability, efficiency, and aging behavior EV, Power Tools, Grid)

Resistance Growth Over Time:

The increase in internal resistance with cycling and calendar aging

Enables lifetime power prediction and end-of-life criteria definition EV, Aerospace, Grid)

Self-Discharge Rate:

The rate at which stored energy is lost over time without external load

Enables long-duration storage, standby systems, and infrequently used assets Grid, DOD, Backup Power)

Source: Battery Report 2023 and 2024, Battery Talk: Battery Application Break Down 12/31/2025 Version 3.0)

Extracted from the PDF; charts and images may read imperfectly.