Auxiliary Battery for 2020 Jeep Compass: Essential Upgrade

Upgrade your 2020 Jeep Compass with an auxiliary battery for enhanced power management, improved accessory performance, and reliable starting in demanding conditions. This guide simplifies the process, making it an achievable DIY project for better Jeep performance and peace of mind.

Your 2020 Jeep Compass is built for adventure, but sometimes, it needs a little extra power to keep up. If you’re adding extra lights, a winch, or just want to ensure your Jeep starts reliably after a long day of running accessories, an auxiliary battery can be a game-changer. It’s like giving your Jeep a second heart for power, ensuring your main battery isn’t drained by all the fun stuff. Don’t worry if you’re new to this; we’ll walk through why it’s a smart move and how it works, making it feel simple and totally doable.

Why an Auxiliary Battery for Your 2020 Jeep Compass?

Think of your Jeep Compass as a mobile command center. It powers your engine, your lights, your infotainment system, and sometimes, extra gear you’ve added for trails or camping. Your main battery does a great job with the basics, but when you start running accessories that draw a lot of power, especially with the engine off, your main battery can get stressed and eventually depleted. This is where an auxiliary battery, or a dual-battery setup, shines.

Understanding the Power Drain

Engine Start: Your main battery is designed to deliver a massive jolt of power to crank the engine. This is its primary job.
Accessory Power: Things like powerful LED light bars, winches, refrigerators, rooftop tent motors, sound systems, and even charging multiple devices can pull continuous power.
Engine Off: When the engine is off, your alternator isn’t recharging the battery. Any accessory draw comes solely from the battery’s stored energy.

Reliable Starting: Your main battery stays charged and ready to go.
Extended Accessory Use: Run lights, fridges, and more for longer periods with peace of mind.
Power for Upgrades: Supports demanding additions like winches or advanced audio systems.
Improved Vehicle Longevity: Prevents over-discharging your main battery, extending its lifespan.
Off-Grid Comfort: Enjoy campsite amenities without worrying about a dead battery.

This upgrade isn’t just for extreme off-roaders; it’s for any 2020 Jeep Compass owner who wants more dependable power for their adventures, big or small.

How a Dual-Battery System Works

A dual-battery system essentially adds a second battery to your Jeep and connects it to the main battery in a smart way. The goal is to let both batteries work together but also keep them somewhat separate, so one doesn’t kill the other.

Key Components of a Dual-Battery Setup

1. The Auxiliary Battery: This is your second power source. Its type and capacity are chosen based on your power needs.
2. Battery Tray and Mounting: A secure place to hold the auxiliary battery. This is crucial for safety.
3. Dual-Battery Isolator (or Management System): This is the brain of the operation. It’s a smart device that connects and disconnects the batteries.
When the engine is running: The isolator connects both batteries, allowing the alternator to charge them both.
When the engine is off: The isolator disconnects the auxiliary battery from the main battery. This protects your main battery so it always has enough power to start the Jeep.
4. Wiring and Fuses: Heavy-duty cables to carry the power and fuses to protect the system from electrical faults.
5. Optional: Battery Monitor: A device that shows you the voltage and charge level of your batteries.

The Charging Process

When your Jeep is running, the alternator generates power. The dual-battery isolator directs this power to recharge your main battery first. Once the main battery is topped up, the isolator then directs the excess power to charge the auxiliary battery. This prioritizes starting power, which is essential for a functional vehicle.

The Discharging Process

When you turn off the engine, the isolator automatically senses the change and disconnects the auxiliary battery. This means any accessories you power are drawing from the auxiliary battery only. Your main battery remains isolated and fully charged, ready for your next engine start.

This intelligent management ensures that even if you drain your auxiliary battery completely, your Jeep will still start. It’s a robust and reliable way to add significant power capacity to your 2020 Jeep Compass.

Choosing the Right Auxiliary Battery for Your 2020 Jeep Compass

Not all batteries are created equal, especially when you’re looking for an auxiliary power source. You’ll want a battery that can handle deep discharges and provide consistent power output for your accessories.

Types of Batteries for Auxiliary Use

AGM (Absorbent Glass Mat) Batteries: These are a very popular and excellent choice for auxiliary batteries.
Pros: Spill-proof, vibration-resistant, can be mounted in various positions, and handle deep discharges better than flooded lead-acid batteries. They also have a lower self-discharge rate.
Cons: Can be more expensive than flooded batteries.
Gel Batteries: A type of sealed lead-acid battery.
Pros: Also spill-proof, good deep-cycle performance, and generally require minimal maintenance.
Cons: Can be sensitive to overcharging, which might require a more sophisticated charging system. They can also be more expensive.
Lithium-ion (LiFePO4) Batteries: The premium option.
Pros: Significantly lighter, extremely long lifespan, can be discharged more deeply with less degradation, and charge very quickly.
Cons: Most expensive option and may require a specific type of charging system and isolator designed for lithium batteries.

Amperage-hour (Ah) Rating: This tells you how much power the battery can deliver over time. A higher Ah rating means more capacity.
Deep Cycle vs. Starting Battery: For an auxiliary battery, you want a “deep cycle” battery. These are designed to be discharged to a lower state of charge repeatedly without damage, unlike a starting battery which is meant for short, powerful bursts.
Calculating Your Needs: A simple way to start is to list your accessories, estimate how many amps they draw, and how long you typically run them.
Example: A 50W LED light bar might draw about 4 amps (Watts / Volts = Amps). If you run it for 4 hours, that’s 16 Ah needed (4 amps 4 hours). Add up all your accessories and expected usage.
Remember: It’s wise to choose a battery with a higher capacity than your calculations, and never discharge an AGM or flooded battery below 50% to maximize its lifespan. Lithium batteries can often be discharged to 80-90%.

Basic Voltage-Sensitive Relay (VSR) Isolators: These are the most common and simplest type. They connect the batteries when the alternator voltage is high enough (indicating the engine is running) and disconnect them when the voltage drops. They are generally affordable and effective for basic needs.
Intelligent/Smart Dual-Battery Systems: These are more advanced and can include features like:
Priority Charging: Ensures the main battery is fully charged before charging the auxiliary.
Overcharge Protection: Prevents damage to batteries.
Manual Override: Allows you to manually connect the batteries in specific situations (like a jump-start scenario, though this should be used with caution).
Temperature Compensation: Adjusts charging based on battery temperature.
Specific Lithium profiles: Essential if you choose a lithium-ion auxiliary battery.

Brands like REDARC offer sophisticated battery management systems that go beyond simple isolation, providing comprehensive power control and monitoring.

Key Features to Look For

Current Rating: The isolator needs to handle the maximum current your alternator can produce and the current your accessories will draw. For most Jeep Compass models, an isolator rated for 100-150 amps is usually sufficient.
Compatibility: Ensure it’s compatible with your alternator’s output and the type of auxiliary battery you choose (especially if going with lithium).
Ease of Installation: While all require wiring, some are simpler to integrate than others.

1. Under the Hood (If Space Allows):
Pros: Keeps all electrical components together, convenient for routing wires.
Cons: Limited space; requires careful placement to avoid heat and moving parts. You might need to relocate existing components or use a specialized battery tray designed to fit around existing obstacles.
2. In the Cargo Area:
Pros: More space available, easier to fit larger batteries or multiple batteries, less heat exposure.
Cons: Requires running longer, heavier gauge wires from the alternator to the back of the vehicle, potentially through firewall grommets. Battery needs to be secured in a sealed battery box to prevent acid leaks or fumes from entering the cabin.
3. Toolbox or Specialized Auxiliary Battery Tray: Aftermarket companies often produce trays designed to mount a second battery in specific vehicle models, sometimes utilizing unused space in the engine bay or near the existing battery.

Material: Choose a sturdy metal tray, often powder-coated steel, designed to withstand vibration and the weight of the battery.
Securing the Battery: The battery must be held firmly in place with straps or brackets. A loose battery is a major safety hazard, as it can short circuit, leak acid, or cause damage.
Ventilation: If using a flooded lead-acid battery (though less common for auxiliary), it needs to be properly vented to the outside of the vehicle to prevent dangerous gas buildup. AGM and Gel batteries are sealed and don’t require external venting in the same way, but good airflow around them is still beneficial.

Wiring the Dual-Battery System: A Step-by-Step Guide

This is where the system comes together. Safety is paramount here. Always disconnect the negative terminal of your main battery before starting any electrical work.

Tools and Materials You’ll Need

New Auxiliary Battery: AGM or LiFePO4 recommended.
Dual-Battery Isolator: VSR or smart system.
Auxiliary Battery Tray: And mounting hardware.
Heavy-Duty Battery Cables: Red (positive) and Black (negative), with appropriate gauge for the expected current (e.g., 4 AWG or 2 AWG). Use online cable gauge calculators to ensure you have the right size based on length and expected amps.
Ring Terminals: For connecting cables to battery posts and the isolator.
Inline Fuses or Circuit Breakers: Sized appropriately for each battery circuit.
Wire Loom/Protective Tubing: To protect wires from abrasion.
Crimping Tool: For attaching terminals securely.
Wire Strippers:
Wrench Set/Socket Set: For battery terminals and mounting hardware.
Drill and Bits: If you need to drill mounting holes or pass wires through the firewall.
Multimeter: For testing voltage and continuity.
Safety Glasses and Gloves: Essential PPE.

1. Disconnect Main Battery: Crucial safety step. Locate your main car battery (usually under the hood) and disconnect the negative (-) terminal first, then the positive (+).
2. Install Auxiliary Battery Tray: Find your chosen location and securely mount the auxiliary battery tray using appropriate hardware. Ensure it’s firmly attached to the vehicle chassis.
3. Mount Auxiliary Battery: Place the new auxiliary battery into the tray and secure it with straps or brackets.
4. Install Dual-Battery Isolator: Mount the isolator securely. It’s often best placed near the auxiliary battery or in a central location under the hood. Follow the manufacturer’s instructions for placement and mounting orientation.
5. Wire the Isolator:
Connect to Main Battery Positive (+): Run a red battery cable from the positive terminal of your main battery to the designated “B+” or “Battery 1” terminal on the isolator. Install an inline fuse or breaker on this line, close to the main battery, sized to protect this circuit (e.g., 100A).
Connect to Auxiliary Battery Positive (+): Run another red battery cable from the positive terminal of your auxiliary battery to the designated “Aux” or “Battery 2” terminal on the isolator. Install an inline fuse or breaker on this line, close to the auxiliary battery, sized appropriately (e.g., 100A).
Connect to Ground/Negative (-): Your isolator may have a separate ground terminal. Connect this to a solid chassis ground point. Alternatively, ensure both batteries have a good ground connection to the vehicle chassis via their own negative cables. The negative terminal of both battery cables should be connected to the vehicle’s chassis or engine block. Never run your main power cables directly to the negative battery terminal without connecting to the chassis first.
6. Wire Accessories to Auxiliary Battery: Connect your accessories (lights, fridge, etc.) to the auxiliary battery’s positive terminal (via a fuse block or individual fuses) and to a good chassis ground. If your isolator has an “accessory” or “load” terminal, you might connect some accessories there to be managed by the isolator system. Follow your isolator’s manual.
7. Secure All Wiring: Use zip ties and wire loom to neatly secure all cables, keeping them away from hot or moving engine parts. Ensure no wires are rubbing against the chassis or other components.
8. Double-Check Connections: Carefully inspect all connections. Ensure terminals are tight and all fuses/breakers are correctly installed.
9. Reconnect Main Battery: Reconnect the positive (+) terminal of your main battery, then the negative (-) terminal.
10. Test the System:
Start the Jeep’s engine. The isolator should engage, showing both batteries are charging (voltage should rise).
Turn off the engine. The isolator should disengage (you might hear a click).
* Turn on some accessories. They should draw power from the auxiliary battery. Monitor battery voltage; it should drop slowly, but the main battery should remain unaffected.

For detailed wiring diagrams and specific isolator instructions, always refer to the documentation provided by the manufacturer of your chosen isolator. Resources like Blue Sea Systems can offer general principles of DC electrical systems for vehicles.

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