Batteries that must indicate to users its real time state-of-charge information, either via an integrated indicator display or remotely through electronic communication with host equipment, require the use of a gas gauge to do so. A gas gauge is a sophisticated microprocessor that converts the analog information of a battery’s cells into digital registers that compute into an accurate state-of-charge value for the battery.
The interesting thing about lithium chemistries is that there is no direct correlation between a battery’s voltage and its state-of-charge. There is a correlation however between a battery’s amperage, time of discharge, closed-circuit voltage, temperature and internal resistance and that battery’s state-of-charge. By properly characterizing reasonably foreseeable use cases and collecting those necessary data points, it is possible to accurately predict (and compensate) a battery’s state-of-charge in real time.
Battery manufactures are in the perfect place to acquire this characterization data as they are the original designers. Ultralife offers this service for many of its battery products, including custom battery designs. After the algorithm has been compiled and loaded onto the battery’s microprocessor, a gas gauge for the battery has been created and state-of-charge information can be sent via SMART communications to either integrated indicator displays or host equipment.
