Automatic 20 A 12 V DC-to-DC battery-to-battery charger with built‑in solar input, multi‑stage charging and selectable modes for Lead‑acid, AGM/Gel, Calcium or Lithium‑ion batteries.

• Calcium or Lithium-ion Batteries Function: This powerful, high-quality battery-to-battery charger can charge a 12 V battery from another 12 V battery or from a solar panel; up to 20 A charging current.
• Powerful solar charge controller with overload protection: compatible with solar panels 16.0–25.0 V, maximum solar input 20 A; automatically activates when no battery-to-battery charging is present.
• Fully automatic high-frequency multi-stage charging: bulk, absorption and float stages with pulsed charging to keep temperatures low and extend battery life.
• Easy battery-type selection: push-button switching between Lead Acid, AGM/Gel, Calcium or Lithium‑ion; unit remembers the selected battery type even without power.
• Safe unattended charging: built-in protections against overload, overheating, overvoltage, over-discharge, short circuit and reverse discharge so it can be left permanently connected.
• Continued charging during battery/load use and ignition on/off control: can be set to begin battery-to-battery charging when ignition is on and stop when ignition is off.
• Deep-discharge recovery: soft-start charging programme and a minimum output battery voltage of only 2.0 V to recover batteries with a high depth of discharge.
• Additional features: LED indicators show target charging stage and selected battery type; compatible with any 12 V lead‑acid, AGM, Gel, Calcium or Li‑ion battery; user manual included for wiring and installation.
• Specifications: Battery input voltage 12.5–16.0 V; maximum charging current 20 A; solar input voltage 16.0–25.0 V; maximum solar input current 20 A; bulk charge voltage 14.3 V (AGM/Gel), 14.0 V (Lead Acid), 15.0 V (Calcium), 14.0 V (Li‑ion); float charge voltage 13.5 V; float charge current 100 mA; battery capacity 18–250 Ah; minimum output voltage 2.0 V; dimensions 21 x 13 x 4 cm (8.3 x 5.1 x 1.6 in); weight 900 g (2.0 lb); 1 year manufacturer warranty.

Suitable for caravans, motorhomes and boats to share alternator charging and extend off‑grid runtime via solar. Follow the supplied user manual for correct wiring and safe installation.