How to Add an AUX Battery to Your Infiniti Q50

If you're running a serious audio system, powering accessories off-grid, or just want peace of mind with a backup power source, adding an auxiliary battery to your Infiniti Q50 is one of the best upgrades you can do. In this guide, I'll walk you through exactly how I installed a GloWe Voltage Series 2 LiFePO4 battery in my Q50's trunk — including the wiring, components, and lessons learned.

Why LiFePO4 Instead of AGM?

Traditional AGM batteries are heavy, slow to charge, and only give you about 50% usable capacity before you risk damage. LiFePO4 (lithium iron phosphate) changes the game:

• Weight: The GloWe S2 weighs just 12 lbs vs. 40+ lbs for a comparable AGM
• Usable capacity: You can safely use 90-100% of the 48Ah rated capacity
• Cycle life: 3,000+ cycles vs. 300-500 for AGM
• Discharge rate: 460A continuous, 600A burst — enough for a 12,000W amplifier
• Built-in BMS: Overcharge, over-discharge, and short-circuit protection built right in

The GloWe Voltage Series 2 is specifically designed for car audio and 12V accessory applications. At 10.5" × 6.5" × 8.5", it fits perfectly in the Q50's trunk side well.

What You'll Need

Core Components

Wiring & Protection

Wiring Diagram

Here's how everything connects. Study this before you start — understanding the full circuit will save you from mistakes.

Step-by-Step Installation

Step 1: Initial Battery Charge

The GloWe S2 ships at 10-11V due to shipping regulations. You must fully charge it with a LiFePO4-compatible charger before installing. Do not connect it to your vehicle's electrical system at shipping voltage — the alternator will try to dump maximum current into it.

Step 2: Plan Your Wire Route

The power wire needs to run from your engine bay battery to the trunk — roughly 15-18 feet in a Q50. The cleanest route:

1. From the main battery positive terminal, through an ANL fuse holder (within 18" of the terminal)
2. Through the firewall via the rubber boot near the clutch pedal area — use a rubber grommet to seal the penetration
3. Along the driver-side rocker panel, under the door sill covers
4. Through the rear seat area and into the trunk

Wrap the engine bay section in high-temperature electrical tape. Use split loom for the interior run to protect against chafing.

Step 3: Mount the Aux Battery

The Q50's trunk side well is the ideal location. The GloWe S2 at 10.5" × 6.5" × 8.5" and only 12 lbs fits comfortably. Secure it with a battery tray and hold-down straps — you don't want 12 lbs sliding around in a hard stop.

Step 4: Install the DC-DC Charger

Mount the Victron Orion-Tr Smart 12|12-30 in the trunk near the aux battery. This is the brain of the system — it takes the variable voltage from your alternator and converts it to a proper LiFePO4 charge profile (14.2V absorption, 13.5V float).

Why not just use an isolator? A simple VSR (voltage-sensitive relay) connects both batteries directly. LiFePO4's extremely low internal resistance means your alternator sees it as a near-short-circuit and dumps maximum current — which can overheat the alternator. The Q50's smart alternator also doesn't play well with passive isolators. A DC-DC charger regulates current draw and provides proper charge stages.

Step 5: Wire It Up

Use ferrules on every wire end and heat shrink on every connection. No exceptions. Here's the connection order:

1. Main battery (+) → ANL fuse #1 (150A) → 0 AWG red wire through firewall → DC-DC charger input (+)
2. DC-DC charger output (+) → ANL fuse #2 (150A) → Aux battery (+)
3. Aux battery (−) → 0 AWG black wire → chassis ground point (bolt to bare metal in trunk)
4. DC-DC charger input (−) → chassis ground point (engine bay or trunk)

Step 6: Install the Battery Monitor

The Dioche Battery Monitor lets you keep tabs on both your main and aux battery voltage from your phone via Bluetooth. Wire the shunt inline with the aux battery's negative cable. I also have one on my main battery — peace of mind knowing both batteries are healthy at a glance.

Step 7: Test Everything

1. With the vehicle off, verify aux battery voltage reads 13.2-13.4V (full LiFePO4)
2. Start the vehicle — the DC-DC charger should activate and begin charging
3. Check that the charger is pulling 25-30A (the Victron has Bluetooth monitoring built in)
4. Verify main battery voltage stays above 13.5V while the aux charges
5. Turn off the vehicle — verify the aux battery holds voltage with no parasitic drain

What Can You Power?

With 48Ah of LiFePO4 capacity, you've got serious juice:

• Car audio: Run a 2,000W amp system for hours without touching your main battery
• Dash cam parking mode: Days of recording without drain risk
• Camping/tailgating: Power a 12V fridge, lights, or a small inverter
• Emergency backup: If your main battery dies, the aux is completely isolated and unaffected

Common Mistakes to Avoid

1. Skipping the fuse at the main battery. With two batteries, power is live from both directions. Every positive connection needs a fuse within 18" of its battery.
2. Using a simple isolator instead of a DC-DC charger. Your Q50's smart alternator and LiFePO4 chemistry both demand regulated charging.
3. Undersized wire. For a 15-18ft run, 0 AWG OFC is the minimum. Voltage drop is real — don't cheap out with 4 AWG.
4. Connecting to the OEM negative terminal. Use chassis ground. The battery current sensor exists for a reason.
5. Skipping ferrules. Bare stranded wire in a set-screw terminal will loosen over time. A $10 bag of ferrules prevents a fire.
6. Not charging before install. The battery ships at 10-11V. Connect it at that voltage and your alternator will work overtime trying to charge it.

Final Thoughts

This install took me about 3 hours, and it's one of the best mods I've done to my Q50. The GloWe Voltage Series 2 is a beast — 48Ah of LiFePO4 in a 12 lb package that fits perfectly in the trunk. Combined with the Victron DC-DC charger for proper charging and the Dioche battery monitor for keeping an eye on things from my phone, the system just works.

If you've got questions about the install or want to see more Q50 builds, drop us a line at support@squarewheelsauto.com.

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