Renogy 12V 40A DC-DC On-Board Battery Charger

Renogy 12V 20A/40A DC-DC Battery Charger with MPPT

The Renogy 12V DC-DC Battery Charger with MPPT is a versatile on-board charger that keeps your auxiliary (house) battery reliably topped up from two sources — your vehicle’s alternator while driving, and solar panels when parked. Available in 20A (RBC20D1U) and 40A (RBC40D1U) models, it combines a DC-DC alternator charger and an MPPT solar charge controller in a single compact unit.

Compatible with both traditional and smart alternators and with a full range of battery chemistries — SLD/AGM, Gel, Flooded, and Lithium (LiFePO4) — it’s the ideal charging hub for RVs, caravans, camper vans, boats, and off-grid dual-battery systems.

Key Features

• Dual-input charging — alternator (DC-DC) and solar (MPPT) in one unit
• Available in 20A and 40A models
• Built-in MPPT solar charge controller for maximum solar harvest
• Compatible with traditional and smart DC alternators (IGN signal wire for smart alternators)
• Supports SLD/AGM, Gel, Flooded, and Lithium (LiFePO4) batteries
• One-touch Battery Type Setting Button with colour-coded LED
• User Mode for fully customisable charging parameters
• Adjustable charging current (20A: 20A/10A · 40A: 40A/30A/20A/10A)
• Battery Temperature Sensor support (for lead-acid batteries)
• Bluetooth monitoring via the DC Home app with the Renogy BT-2 module
• Long-range monitoring and control via Renogy ONE Core
• App-based parameter setting, diagnostics, and fault alarms

Two Ways to Charge

While you drive, the DC-DC charger draws from your vehicle’s alternator to charge the auxiliary battery quickly and safely — with a dedicated IGN signal wire connection for smart alternators. When parked, the built-in MPPT solar charge controller harvests power from your solar panels, so your house battery stays charged whether you’re on the move or off-grid.

Wide Battery Compatibility & Easy Setup

A single Battery Type Setting Button lets you switch between battery types, with an LED that changes colour to confirm your selection — SLD/AGM, Gel, Flooded, or Lithium (with lithium activation enabled). Settings synchronise automatically between the charger and the DC Home app. For advanced users, User Mode unlocks fully customisable charging parameters (boost, float, equalisation, voltage thresholds, and more) directly in the app.

Charging Current Overview

Smart Monitoring & Control

Add the Renogy BT-2 Bluetooth Module (via the RS485 port) for short-range monitoring and programming through the DC Home app — track real-time input/output voltage and current, adjust charging parameters, and receive fault alarms. For long-range, cloud-connected monitoring, pair the charger with the Renogy ONE Core, which links to the DC Home app over Wi-Fi so you can keep an eye on your system from anywhere.

Battery Temperature Compensation

An optional Battery Temperature Sensor measures the ambient temperature around the battery and compensates the float charge voltage when it’s cold — protecting battery health. (Note: the temperature sensor should not be used on LiFePO4 batteries that have their own built-in BMS.)

Ideal Applications

• RVs, caravans, and motorhomes
• Camper van and 4×4 dual-battery builds
• Boats and marine installations
• Overlanding and off-grid setups
• Auxiliary/house battery charging systems
• Solar-plus-alternator hybrid charging

Important Setup Note

Always set the correct battery type before use — an incorrect battery type setting can damage the charger and voids the warranty. When using User Mode or customising a preset, consult your battery manufacturer’s recommended charging parameters first.

Choose the Renogy 12V 20A/40A DC-DC Battery Charger with MPPT for smart, dual-input charging that keeps your auxiliary battery powered from both alternator and solar — the reliable heart of any RV, marine, or off-grid dual-battery system.