Owing to its superior characteristics, lithium titanate batteries have been widely adopted in energy storage systems, rail transit, military industry, and scientific exploration. Domestic research and pilot applications have explored replacing traditional lead-acid batteries with lithium titanate batteries in substation DC power systems. This study investigates the influencing factors for battery operating voltage setting and capacity selection in lithium titanate battery system design based on battery characteristics and substation DC power requirements. It further analyzes the effects of long-term float charging on lithium titanate batteries and proposes mitigation strategies. Measures such as optimizing float voltage, implementing intermittent charging, and utilizing smart BMS with active equalization control are introduced to reduce degradation from prolonged float charging.