If you own a Vanagon and dream of extended off-grid adventures, a dual battery system with a proper isolator is essential. This quick guide will walk you through everything you need to know about battery isolators, why they’re crucial, and how to choose the right one for your VW Vanagon.
What Is a Battery Isolator and Why Do You Need One?
A battery isolator is an electrical device that allows your Vanagon’s alternator to charge both your starting (main) battery and auxiliary (house) battery simultaneously while keeping them electrically separate when the engine is off. This separation is critical because it ensures your vehicle will always start reliably, even if you’ve drained your auxiliary battery running appliances like fridges, lights, or other camp accessories.
Without an isolator, you risk draining your starting battery when using accessories, potentially leaving you stranded with a vehicle that won’t start. The isolator acts as an intelligent switch, managing power flow between your batteries to maintain the starting battery’s charge.
Max Battery Size Under Vaangon Seat
The space beneath a VW Vanagon driver’s seat can accommodate a maximum battery size of approximately 10.5″ length × 6.75″ width × 8″ height (267mm × 171mm × 203mm), which typically allows for Group 24 or Group 27 batteries. This limited space requires careful measurement before purchasing an auxiliary battery.
Most Vanagon owners successfully install a Group 24 AGM or deep cycle battery in this location, though some have modified the seat bracket slightly to fit Group 27 batteries with additional capacity. The factory Westfalia models used this under-seat location for their auxiliary batteries, demonstrating its practicality.
When selecting a battery, consider not only physical dimensions but also terminal orientation, as side terminals are often easier to connect in this confined space. Always ensure at least 1/2″ clearance around the battery for proper ventilation and secure mounting to prevent movement during driving.
Popular Battery Isolator Options for Vanagons
1. Intelligent Isolator Wiring Kit (Van Cafe)
This advanced battery management system offers several benefits:
- Prioritizes charging your starting battery first until it reaches 13.2V, then diverts charge to your auxiliary battery
- Features a safety function that parallels both batteries if your starting battery is low, helping with engine starts
- Comes with pre-cut, terminated wires and all necessary installation hardware
- Works well with traditional lead-acid and AGM batteries (note: not compatible with lithium batteries)
2. 2nd Battery Isolator Solenoid (GoWesty)
For those seeking a straightforward and reliable solution:
- Used in GoWesty’s popular auxiliary battery kits
- Automatically connects batteries when the engine runs and isolates them when off
- Compatible with all Vanagon models from 1980 to 2003
- Cost-effective option for basic dual battery setups
3. Dual Battery Relay Kit (Bus Depot)
Designed to mirror the factory dual battery setup found in Westfalia models:
- Includes a fused relay, necessary wiring, and clear instructions
- Works automatically with your ignition key
- Simple yet effective design prevents starting battery discharge
- Ideal for those wanting a setup similar to factory Westfalia configurations
Installation Basics
Most Vanagon owners install the auxiliary battery under the driver’s seat, which offers a convenient location with adequate space. When installing your battery isolator:
- Follow the manufacturer’s instructions carefully – many suppliers like Van Cafe provide detailed PDF guides
- Ensure all connections are secure and properly fused
- Use appropriate gauge wire for your system’s amperage requirements
- Verify compatibility between your isolator and battery type before installation, especially if using lithium batteries
Real-World Performance
Vanagon owners report significant improvements after installing battery isolators. With proper installation using heavy-gauge wire (4-gauge is recommended by many), you can achieve consistent charging voltages between 13.5 and 13.9 volts across both batteries. This ensures reliable starting power and sufficient auxiliary power for your camping or travel needs. Check out our guide on the proper way to jump-start a vehicle.
Conclusion
A battery isolator is a worthwhile investment for any Vanagon owner looking to enhance their vehicle’s electrical capabilities. By selecting the appropriate isolator for your needs and following proper installation procedures, you’ll gain the freedom to use electrical accessories without worry, knowing your Vanagon will start reliably every time.
Whether you choose an intelligent management system, a simple solenoid, or a relay kit, the right battery isolator will significantly improve your Vanagon’s off-grid capabilities and overall reliability.
