Victron Buck-Boost DC-DC Converter

The Victron Buck-Boost DC-DC Converter is a fully programmable, non-isolated DC-DC converter designed to charge a 12V or 24V service (auxiliary) battery in vehicles equipped with a smart alternator — where the alternator output is controlled by the vehicle's onboard electronics and may not deliver sufficient or consistent charging voltage to the service battery. Available in three output current ratings — 25A, 50A, and 100A — all models feature automatic buck/boost control, engine-running detection, adjustable current limiting, M8 connections, USB configuration, and an onboard battery monitor, making them the professional solution for controlled auxiliary battery charging in camper vans, trucks, buses, and professional vehicles.

Modern Euro 5 and Euro 6 vehicles use intelligent alternator control systems that reduce alternator output voltage at cruise speed to recover energy during deceleration — a fuel-saving measure that also means the alternator often produces insufficient voltage to properly charge a service battery connected in parallel. The Buck-Boost converter solves this by accepting any input voltage between 10V and 30V and producing an independently regulated output voltage also between 10V and 30V — using automatic buck or boost control to maintain the correct charge voltage at the service battery regardless of whether the alternator output is above or below the target charge voltage.

The converter activates automatically when the engine is running — detected via an engine-running detection protocol on the ignition or via a dedicated input wire — and deactivates when the engine stops, preventing battery drain when parked. Two output pins (maximum 1A each, output voltage equal to input voltage) can be used to activate or deactivate external loads or relays based on engine-running status. An optional battery temperature sensor input enables temperature-compensated charging. All settings — including output voltage, current limit, and charge algorithm — are fully configurable via USB connection to a PC using dedicated Victron software.

Features

Automatic Buck/Boost Control — Works with Any Smart Alternator

Accepts any input voltage between 10V and 30V and automatically applies either buck (step-down) or boost (step-up) conversion to maintain a stable, correctly regulated charge voltage at the service battery — regardless of whether the alternator output is above or below the target charge voltage at any given moment.

Fully Programmable via USB

All converter parameters — including output voltage, charge current limit, charge algorithm, low voltage cut-off, and engine-running detection thresholds — are fully configurable via USB connection to a PC using dedicated Victron configuration software, enabling precise customisation for any vehicle and battery type.

Automatic Engine-Running Detection and Activation

The converter activates automatically when it detects the engine is running — via an alternator input signal or ignition wire — and deactivates when the engine stops. This prevents the service battery from discharging the starter battery when the vehicle is parked, without requiring any manual switching.

Adjustable Current Limiter — Alternator Protection

The maximum output current is adjustable and enforced precisely — preventing the combined load of the alternator charging both batteries from exceeding the alternator's rated capacity. This is particularly important in lithium battery installations where a depleted lithium service battery could otherwise overload a standard alternator.

Two Auxiliary Output Pins — Load Activation and Deactivation

Two output pins (1A each, output voltage equal to input voltage) can be used to activate or deactivate external relays, DC loads, or accessories based on engine-running status — enabling automatic switching of refrigerators, auxiliary heaters, or other vehicle equipment with the engine state.

Battery Monitor — State of Charge and Current Measurement

A built-in battery monitor tracks output current and battery state of charge in real time — providing visibility of service battery charging progress and status via the USB configuration interface and optional LED indicators on the converter front panel.

Optional Temperature Sensor Input

An optional battery temperature sensor can be connected to the temperature monitoring input — enabling temperature-compensated output voltage adjustment for accurate charging across a wide range of ambient temperatures, particularly important for lead-acid batteries in cold climates.

Available in 25A, 50A, and 100A

Available in three output current ratings to suit different auxiliary battery bank sizes and vehicle electrical loads — 25A (300W at 12V), 50A (600W at 12V), and 100A (1200W at 12V) — all with the same input/output voltage range, feature set, and configuration interface.

Specifications

Datasheets and Manuals

Datasheet

Product Manual