bq27Z561-R2 Impedance Track™ Gas Gauge IC Texas Instruments bq27Z561-R2 Impedance Track™ Gas Gauge IC is a highly integrated, accurate 1-series cell gas gauge with a flash programmable custom reduced instruction-set CPU (RISC). It includes SHA-256 authentication for li-ion and li-polymer battery packs. The 1-series cell capability includes parallel cells for increased capacity.