If you’re building a capable off-grid adventure vehicle, a dual battery setup is one of the smartest upgrades you can make. Whether you’re powering a fridge, LED lights, or charging gear at camp, a dedicated auxiliary battery system keeps your essentials running—without draining your starter battery.
In this post, I walk you through the installation and function check of the Vevor 140 Amp Voltage-Sensing Split Charge Relay in my Volvo XC70. This upgrade transforms the XC70 from a comfortable soft-roader into a reliable overlanding and expedition-ready rig.
🔧 What This Setup Does
The Vevor 140A relay automatically detects when the engine is running and connects the starter battery to the auxiliary battery. When the vehicle is off, the relay isolates the two, ensuring you never kill your starting power while using accessories.
This system is:
- Efficient
- Budget-friendly
- Simple to install
- Perfect for overlanding, vanlife, and soft-roader builds
🛠️ What You’ll Need
Here are the main components I used for the install:(Included with the kit)
- Vevor 140A Voltage-Sensing Split Charge Relay
- 6 AWG cable (for safe, low-resistance power transfer)
- 100A inline fuses (one near each battery)
- Battery terminals
- Heat shrink and crimp connectors
This kit provides solid protection and performance, and can handle most typical 12V adventure gear.
⚡ Installation Overview
The setup connects directly from the starter battery to the auxiliary battery using thick-gauge wire, with inline fuses placed near both battery terminals for safety. The relay is grounded to the chassis and mounted securely within reach of both batteries.
Key steps:
- Route and secure 6 AWG cable between batteries
- Install 100A fuses within 12″ of each battery
- Mount and ground the relay
- Double-check all crimps and heat shrink connections
- Test the system with the engine off and running
Once running, the relay closes the circuit and charges the auxiliary battery. When the engine shuts off, it isolates again to preserve starter power.
🏕️ Why This Setup Rocks
If you’re doing any kind of:
- Bikepacking
- Weekend hiking trips
- Overlanding
- Remote camping
- Vanlife support
…then this simple dual battery solution gives you reliable power anywhere. The Volvo XC70, with its all-wheel drive and wagon versatility, is a fantastic soft-roader platform. This system gives it a serious upgrade in independence and capability.
✅ Final Thoughts
This DIY install is a great intro to automotive electrical work, and the Vevor relay offers solid performance at a budget-friendly price point. If you’re building a self-sufficient vehicle for off-grid adventures, this is a key step.