Owning a Jeep Wrangler means enjoying adventure and rugged performance. But when you hear about the auxiliary battery, you might wonder where it is and why it matters.
Many Jeep owners are surprised to find their Wrangler has a second battery. This small battery plays a big role in how your Jeep’s electronics and start-stop system work.
If you’re searching for the exact location and the purpose of the auxiliary battery, this guide will answer your questions clearly.
What Is The Auxiliary Battery In Jeep Wrangler?
The auxiliary battery is a secondary power source. It’s not used for starting the engine but supports electrical systems. Many Jeep Wranglers, especially models from 2018 and newer, include this battery to help with the engine start-stop system. When you stop at a traffic light, the start-stop system saves fuel by turning off the engine. The auxiliary battery keeps electronics running during this time.
This battery also helps with accessories like radio, navigation, and climate control. It’s much smaller than the main battery. For example, the 2018–2023 Jeep Wrangler JL uses a 12V AGM auxiliary battery with about 200–250 cold cranking amps (CCA). The main battery is larger, usually 600–700 CCA.
Where Is The Auxiliary Battery Located?
Finding the auxiliary battery is not obvious. Jeep didn’t place it in a separate compartment. Instead, it sits in a hidden spot near the main battery. Here’s how to locate it step-by-step:
- Open the hood. The batteries are under the hood, on the passenger side.
- Find the main battery. It’s the bigger battery near the firewall.
- Look for the battery tray. The auxiliary battery sits in the same tray as the main battery, but underneath it.
- Sometimes, a plastic cover hides both batteries. Remove it to see the batteries clearly.
- The auxiliary battery is about the size of a deck of cards, much smaller than the main battery.
Below is a comparison of battery locations and sizes:
| Model Year | Main Battery Location | Auxiliary Battery Location | Auxiliary Battery Size |
|---|---|---|---|
| 2018–2023 Wrangler JL | Under hood (passenger side) | Under main battery tray | Small, 12V AGM |
| 2011–2017 Wrangler JK | Under hood (passenger side) | No auxiliary battery | Not applicable |
| 2024 Wrangler | Under hood (passenger side) | Under main battery tray | Small, 12V AGM |
Why Does The Auxiliary Battery Matter?
The auxiliary battery is crucial for modern electronics. Without it, your start-stop system and accessories might not work correctly. If this battery fails, you may see warning lights or lose features like auto start-stop. Replacing it is important for smooth operation.
Most drivers overlook this small battery. Mechanics often report that faulty auxiliary batteries cause mysterious electrical issues.
For example, a Jeep Wrangler owner might notice the radio or air conditioning shuts off when the engine stops at a light. This usually means the auxiliary battery is weak or dead.
How To Replace The Auxiliary Battery
Changing the auxiliary battery is more difficult than the main battery. You can do it yourself, but it takes patience and a few tools.
- Disconnect the main battery first for safety.
- Remove the main battery from the tray.
- Locate the auxiliary battery underneath. It’s held by a bracket or clips.
- Remove the bracket and disconnect the terminals.
- Replace with a new 12V AGM auxiliary battery.
- Reinstall the main battery and reconnect everything.
Below is a quick comparison of replacement difficulty:
| Battery Type | Replacement Steps | Average Time | Skill Level |
|---|---|---|---|
| Main battery | Remove cover, disconnect terminals, swap battery | 10–15 minutes | Beginner |
| Auxiliary battery | Remove main battery, remove bracket, swap battery | 30–45 minutes | Intermediate |
Tip: Always use the correct battery type. Jeep uses AGM batteries for both main and auxiliary to handle frequent start-stop cycles.
The auxiliary battery can cause issues if neglected. Here are problems Jeep owners often face:
- Auto start-stop failure: If the battery is dead, the system won’t work.
- Warning lights: Dashboard may show battery or start-stop warnings.
- Accessory power loss: Radio, AC, and navigation may turn off during stops.
- Battery drain: A weak auxiliary battery can drain the main battery faster.
Many people mistake these problems for larger electrical faults, but replacing the auxiliary battery often fixes them. It’s a small part, but it keeps many systems running.
How The Auxiliary Battery Works With The Main Battery
Both batteries are connected through a relay system. When the engine stops, the relay switches power to the auxiliary battery. When the engine starts again, the main battery takes over. This process happens in seconds.
Below is a simple comparison of roles:
| Function | Main Battery | Auxiliary Battery |
|---|---|---|
| Engine starting | Yes | No |
| Start-stop power | No | Yes |
| Accessory support | Yes | Yes (during stops) |
| Charging | Alternator | Alternator (via relay) |
Auxiliary Battery Maintenance Tips
To keep your Jeep running well, check the auxiliary battery every 12 24 months. Look for corrosion or swelling. Use a voltmeter to check voltage healthy batteries show 12. 4 12. 7 volts. If voltage drops below 12V, consider replacing it.
Two insights many beginners miss:
- The auxiliary battery can fail before the main battery, causing hidden electrical issues.
- If you remove the auxiliary battery, some systems may not work, even if the main battery is fine.
If you want more details about battery care, visit the official Jeep site: Jeep Research.
Frequently Asked Questions
Where Is The Auxiliary Battery In Jeep Wrangler Jl?
The auxiliary battery is under the main battery tray, on the passenger side under the hood. You must remove the main battery to access it.
Can I Drive Without The Auxiliary Battery?
You can drive, but many features like auto start-stop and accessory power during stops may not work. It’s not recommended for long-term use.
How Often Should I Replace The Auxiliary Battery?
Most Jeep mechanics suggest every 2–3 years or when you notice electrical problems. Climate and driving habits affect battery life.
Does Every Jeep Wrangler Have An Auxiliary Battery?
No. Only newer models (2018 and up, JL series) have it. Older JK Wranglers do not use an auxiliary battery.
Is The Auxiliary Battery Expensive To Replace?
The battery itself costs around $50–$100. Labor can add another $100–$150 if done at a shop. Doing it yourself saves money but takes time.
Knowing where the auxiliary battery is in your Jeep Wrangler helps you keep your vehicle in top shape. It’s a small part with a big impact.
If you understand how it works and how to replace it, you’ll avoid common electrical problems and save money on repairs.
