Meet the Mastervolt Charge Mate Pro 90 (Model: 83309002) — a smart electronic charge coupling designed for seamless dual-battery charging with minimal voltage drop. It enables effective distribution of charging current between two battery banks, so your starter and service batteries stay ready when you need them.

Key advantages

• Unidirectional protection that blocks return current under all circumstances, preventing power dips in your onboard electrical network.
• Priority charging ensures the primary (starter) battery is charged first, reducing the risk of a flat engine battery.
• All battery types supported, including Lithium Ion, with a dedicated charge solution for a secondary battery if needed.
• High current capability up to 90 A output, with the secondary battery charging limited to 40 A, making it ideal for larger alternators and Li‑ion packs.
• Robust, marine-grade design featuring IP65 electronics in a corrosion‑resistant housing with aluminum heat sinks for reliable performance at sea or on land.
• Easy installation and universal compatibility with all chargers and alternators. The unit supports parallel configurations for even higher power demands.
• LED status monitoring provides clear warnings and operation cues for quick diagnostics.
• Remote operation options with on/off/auto/start assist controls and an emergency start bypass (optional), giving you flexibility in how you manage charge and start routines.
• Two battery outlets with automatic 12/24 V detection, enabling simple setup for two battery banks (starter and service).
• Marine-ready example – connect a bow thruster or other auxiliary battery and ensure the service battery remains charged while maintaining power to essential systems.

Specifications

• Output current: 90 A (secondary battery charging limited to 40 A)
• Input voltage range: 9–32 V
• Number of battery outlets: 2
• Battery voltage automatic detection: 12/24 V
• Remote switch functions: On, Off, Auto, Start Assist
• Dimensions (HxWxD): 6.2 x 5.5 x 3.1 inches
• Weight: 1.9 lb
• Connection: 3 x fast-on connectors (switch, ground and status)
• Battery types: All types (Lithium Ion protection via multipurpose contact)
• Protection: IP65 electronics in a corrosion-resistant casing with aluminum heat sinks