Alternator to Battery Chargers

What Does an Alternator to Battery Charger Do?

An alternator to battery charger (AB series) places a controlled load on the alternator, pulling its output voltage down to approximately 13V. This forces the alternator's standard regulator to operate at full current. The charger then takes that high-current, low-voltage input and amplifies it to a regulated charging voltage, delivering intelligent, software-controlled, 4-stage charging to the auxiliary battery bank, including temperature compensation.

The result: auxiliary batteries receive up to 50% more charge current and charge up to 5 times faster than they would through a direct alternator connection.

Who Should Use an AB Series Alternator to Battery Charger?

The Sterling Power AB series suits marine vessels, North American RVs, and off-grid vehicles running traditional alternator systems with lead-acid or AGM auxiliary batteries. It supports single or multiple alternators and charges multiple battery banks simultaneously through its built-in split-charging function.

The AB series is not recommended for:

• Modern Euro 5/6 vehicles (Ford, VW, Mercedes, Renault, Citroën) or Japanese vehicles with regenerative braking systems, use the Sterling Power BB (battery to battery) series instead
• Lithium battery banks without an external current limiter, the AB system maximizes available current without limiting draw, which can overload lithium cells

If your setup includes lithium batteries or a smart alternator, browse the Battery to Battery Chargers collection.

How Do You Choose the Right Alternator to Battery Charger Amperage?

The model number tells you the maximum total alternator input. AB1280 accepts up to 80A total input; AB12160 accepts up to 160A. Match the unit to your alternator's rated output, or the combined output if running dual alternators.

12V Models

• AB1280: Supports up to 80A alternator input.
• AB12130: Supports up to 130A alternator input.
• AB12160: Supports up to 160A alternator input.
• AB12210: Supports up to 210A alternator input.
• AB12300: Supports up to 300A alternator input.
• AB12400: Supports up to 400A alternator input.

24V Models

• AB2480: Supports up to 80A alternator input.
• AB24100: Supports up to 100A alternator input.
• AB24200: Supports up to 200A alternator input.

If you're unsure which unit suits your alternator, contact Volts Energies, our team will confirm compatibility before you order.

Key Features of the Sterling Power AB Series

• 4-stage intelligent charging, bulk, absorption, float, and de-sulphation, with temperature compensation
• No alternator modification required, installs between the alternator output and battery bank
• Multi-alternator compatible, supports one or two alternators on a single unit
• Built-in split charging, charges starter and domestic battery banks simultaneously; starter battery always takes priority
• Alternator overtemperature protection, temperature sensors disengage charging before the alternator overheats
• Optional remote control, displays live voltage, current, and temperature readings
• Battery de-sulphation, extends AGM and lead-acid battery lifespan

Alternator to Battery Charger vs. Battery to Battery Charger: Which Do You Need?

The right charger depends on your vehicle, battery type, and charging system.

Choose an AB Series (Alternator to Battery Charger) if you:

• Need to install the charger between the alternator and battery bank.
• Have a traditional alternator without smart charging technology.
• Are building a marine system, North American RV, or conventional engine setup.
• Can use an external current limiter when charging lithium batteries.

Choose a BB Series (Battery to Battery / DC-DC Charger) if you:

• Need to install the charger between the starter battery and auxiliary battery.
• Have a smart alternator or a vehicle with regenerative braking.
  Are charging lithium batteries, as the charger includes built-in current limiting.
• Are building a modern van, Euro 5/6 vehicle, or any system that requires DC-DC charging.

Shop the Battery to Battery Chargers collection for DC-DC solutions compatible with Victron Orion-Tr Smart and Sterling Power BB series units.

FAQs

What Does An Alternator To Battery Charger Do?

It connects between your alternator and auxiliary battery bank. The charger pulls the alternator to full output, then delivers a regulated 4-stage charge to your batteries, up to 5 times faster than a direct alternator connection alone.

Do I Need To Modify My Alternator To Use An AB Series Charger?

No. The AB series installs between your existing alternator output and your battery bank with no alternator modifications required.

Can The Sterling Power AB Series Charge Lithium Batteries?

Not without an external current limiter. The AB series maximizes available current without limiting draw, which can overload lithium cells. If you run lithium batteries, the Battery to Battery (BB) series is the better fit.

Will An AB Series Charger Work With My Modern Van Or Euro 5/6 Vehicle?

No. Vehicles with smart alternators or regenerative braking, including most modern Ford, VW, Mercedes, Renault, and Citroën models, should use the Sterling Power BB series instead.

How Do I Know Which Amperage Model I Need?

Match the model number to your alternator's rated output. For example, the AB1280 handles up to 80A total input, while the AB12400 handles up to 400A. If you run dual alternators, add their combined output together.

Can One AB Series Unit Charge Multiple Battery Banks?

Yes. The AB series has a built-in split-charging function that charges your starter and domestic battery banks at the same time, with the starter battery always taking priority.

Does The AB Series Protect Against Alternator Overheating?

Yes. Built-in temperature sensors monitor the alternator and disengage charging before it overheats.

What's The Difference Between The AB Series And The BB Series?

The AB series installs between the alternator and battery bank and suits marine vessels and traditional North American RVs with lead-acid or AGM batteries. The BB series installs between the starter and auxiliary battery, and works with smart alternators, regenerative braking vehicles, and lithium battery banks.