Compact SJ20 automatic step-up/step-down MPPT forward/backward converter power supply module with an adjustable board for flexible solar charging and lithium battery management - Charges lithium batteries and supports professional solar charging for off-grid or backup systems - LED constant-current driver provides a stable current for LEDs and for battery charging control - Visual adjustment of the tracking point voltage lets you optimize MPPT efficiency for your panel and battery - Compact PCB based module designed for easy integration into DIY projects, enclosures, or control boards - Forward and backward conversion with automatic stepping expands input/output compatibility for common solar panels and lithium packs - Adjustable output and tracking settings improve charging speed, battery protection, and overall system performance Use scenarios - Off-grid cabin solar charger with a lithium battery bank - DIY portable solar generator or emergency backup pack - Solar lighting or signage projects that require a reliable constant-current LED driver