Battery Guard addresses a critical aspect of mobile device maintenance by implementing scientifically-supported battery preservation techniques. Developed by x1y9, this Android application focuses on extending lithium battery lifespan through controlled charging patterns rather than conventional battery saving methods. The app occupies a niche position in the utility market, targeting users who prioritize long-term device health over immediate power availability. The core functionality revolves around customizable charge thresholds that enable shallow discharge cycles. Users can set both upper and lower percentage limits (typically 80-90% for high threshold and 20-30% for low threshold), with the app providing audible and visual alerts when these boundaries are reached. This approach leverages lithium battery research indicating that partial charging cycles significantly reduce battery degradation compared to full 0-100% cycles. The application operates as a background service with minimal resource consumption, consistently monitoring battery levels without requiring constant user interaction. User experience centers around a minimalist interface that prioritizes functionality over aesthetic complexity. The main screen displays current battery percentage alongside configurable slider controls for threshold settings. Notification preferences allow customization of alert types and frequencies. Real-world usage patterns show the app most effectively serves users with consistent charging routines, particularly those who charge devices overnight or during work hours. The lightweight design ensures negligible impact on system performance, though continuous background monitoring does require persistent notification presence. No user reviews are currently available for detailed analysis of real-world implementation experiences. The absence of user feedback makes comprehensive assessment challenging, though the 4.06 rating suggests generally positive reception among those who have installed the application. Without specific user testimonials, performance evaluation relies primarily on technical specifications and battery science principles rather than crowd-sourced experiences. The application demonstrates clear strengths in implementing scientifically-validated battery preservation techniques through an efficient, lightweight package. However, limitations include the requirement for user discipline in responding to alerts and the potential inconvenience of maintaining partial charge states. Battery Guard proves most valuable for device owners planning long-term usage, particularly those using premium smartphones where battery replacement costs justify behavioral adjustments. The app serves less practical purpose for users frequently requiring maximum battery capacity or those replacing devices frequently.