Navy

Lithium-Ion battery state-of-health monitor

Single-point diagnostic to determine instability of a single lithium-ion battery cell within a rechargeable battery pack

Energy
The US Navy has developed a fast, simple, and highly sensitive diagnostic to assess the health of individual cells within a battery pack. Damage to a single cell can be detected and the relative impairment level reported from minor (green) to severe (red)

The US Navy has developed a fast, simple, and highly sensitive diagnostic to assess the health of individual cells within a battery pack. Damage to a single cell can be detected and the relative impairment level reported from minor (green) to severe (red).

The US Naval Research Laboratory (NRL) has developed a diagnostic tool that tests entire battery packs to determine in real-time if a cell within the pack has suffered damage without the need to individually test each cell separately. A single damaged cell can create an unreliable or even dangerous situation even though the battery pack as a whole exhibits “normal” voltage behavior. NRL’s diagnostic applies a small AC current or voltage to a battery at a specific frequency which is invariant with battery state-of-charge. Changes in the impedance response are indicative of damage or abuse within the cells.

The NRL single-point diagnostic technology can operate as a stand-alone diagnostic or in real-time as part of an online monitoring system. Testing has demonstrated that the diagnostic is sensitive enough to detect a single overcharge event in one cell of a battery pack. Thresholds can be established to indicate relative damage and safety levels of a battery pack, from a unit that has a single cell that is starting to fail up to a unit that is nearing catastrophic failure.

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