The FLUKE-BT521ANG is an advanced battery analyzer from the Fluke 500 Series designed for comprehensive testing and maintenance of stationary batteries of all types. It measures internal battery resistance, DC and AC voltage, DC and AC current, ripple voltage, frequency, and temperature using an integrated intelligent test probe with LCD display and infrared temperature measurement capability. The instrument features automatic or manual sequence testing of battery strings with automatic measurement storage, threshold comparison with configurable reference values for resistance and voltage, and wireless communication for data download and remote display via the dedicated mobile app. The angled test probe design provides long reach for double-stacked cells, while the ergonomic rugged coaxial two-pole Kelvin test pins with remote SAVE button reduce test time and increase efficiency. With 7.4 V 3000 mAh lithium-ion battery providing over eight hours of continuous operation, CAT III 600 V safety rating, and included battery management software for trend analysis and PDF report generation, the BT521ANG is ideal for maintenance, troubleshooting, and performance testing of battery systems in data centers, UPS installations, and other critical power applications.