Sterling Power AB12400 12V 400A Alternator to Battery Charger

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Sterling Power AB12400 — 12V / 400A Alternator to Battery Charger

The Sterling Power AB12400 is the largest and most powerful unit in Sterling's Alternator to Battery (AB) series — a high-output, marine-grade charger that transforms your alternator's raw output into a sophisticated 4-stage charge profile for your house or domestic battery bank. At 400A input capacity, it can handle a single large alternator or multiple alternators combined, provided the total input current does not exceed 400A.

The AB series works by placing a controlled load on the alternator, pulling its voltage down to a high-current, low-voltage state, then amplifying that power into a proper 4-stage charging profile at the output — bulk, absorption, float, and equalization. The result is house bank charging up to five times faster than a standard alternator connection, with correct charge voltages that condition battery plates and extend battery life. No modification to the alternator is required, and no interference with engine management systems or ECU wiring is needed for installation.

The AB12400 includes an internal split charge system that maintains a sufficient maintenance charge on the starter battery while prioritizing full 4-stage charging on the house bank. It supports multiple battery chemistries including AGM, gel, flooded lead acid, and LiFePO4, with built-in alternator and battery temperature sensing to protect both the charger and the alternator under sustained load.

Important compatibility note: The AB series is not recommended for modern European or Japanese vehicles equipped with Euro 5/6+ regenerative braking systems or integrated engine management. For these vehicles, Sterling's Battery to Battery (BB) Saturn series is the correct solution. The AB12400 is well suited to traditional American vehicles, older engines, marine applications, and commercial equipment with conventional alternator systems.

Key Specs:

• Input voltage: 12V DC
• Maximum input current: 400A
• Dimensions: 370mm × 288mm × 70mm
• Weight: 5.1 kg
• Compatible battery types: AGM, gel, flooded lead acid, LiFePO4
• Temperature sensing: alternator and battery
• Optional remote control: ABNRC (sold separately)

Not recommended for use with lithium batteries without an external current limiter. The AB series is not current limiting — for lithium installs, Sterling's BB Saturn series DC-DC chargers are the recommended solution.