Replacing the auxiliary battery in your Jeep Wrangler JL may sound tricky, but it’s a manageable task for most people with basic tools. This small battery is crucial for systems like the Start/Stop feature and keeps electronics running smoothly. If your Jeep shows warning lights, slow starts, or electrical glitches, the auxiliary battery could be the culprit. Knowing how to replace it yourself can save money and keep your vehicle reliable.
Understanding The Auxiliary Battery
The auxiliary battery is different from your main battery. It’s smaller, usually around 12 volts and 200-240 CCA (cold cranking amps). Its job is to support electronics when the engine turns off, especially during Stop/Start events.
Many Jeep Wrangler JL owners miss the fact that their vehicle has two batteries. The auxiliary battery is often hidden beneath the main battery, making it easy to overlook during regular maintenance. If your Jeep acts strangely after a few years—like shutting off accessories or not starting reliably—it’s smart to check this battery.
Signs You Need A Replacement
Watch for these symptoms:
- Start/Stop system disabled message
- Flickering lights or slow power windows
- Trouble starting after stops
- Battery warning light on dashboard
If you notice one or more, test the auxiliary battery. It usually lasts 3-4 years, but heavy use can shorten its life.
Tools And Parts Required
Before starting, gather these:
- Replacement auxiliary battery (compatible with Jeep Wrangler JL)
- 10mm and 13mm wrenches or sockets
- Screwdriver (flathead and Phillips)
- Ratchet with extension
- Gloves and safety glasses
Check your owner’s manual or dealer for the correct battery model. Prices range from $40-$80 for quality brands.
Step-by-step Replacement Guide
Follow these steps to safely replace the battery:
1. Prepare Your Jeep
- Park on a level surface.
- Turn off the ignition and remove the key.
- Wait at least 10 minutes to let electrical systems power down.
2. Locate The Batteries
- Open the hood.
- The main battery is in the engine bay’s passenger side.
- The auxiliary battery sits under or beside the main battery, often hidden by a plastic cover.
3. Disconnect The Main Battery
- Using a 10mm wrench, loosen the negative (black) cable from the main battery.
- Move the cable away to prevent accidental connection.
4. Remove Battery Hold-downs
- Unscrew the bolts securing the main battery with a 13mm socket.
- Lift the main battery carefully and set it aside.
5. Access The Auxiliary Battery
- Remove any covers or brackets blocking the auxiliary battery.
- Using a 10mm socket, disconnect the negative cable first, then the positive cable.
6. Remove The Auxiliary Battery
- Unscrew the mounting bracket.
- Lift out the old auxiliary battery. Handle gently to avoid spills or damage.
7. Install The New Battery
- Place the new auxiliary battery in the same position.
- Reattach the mounting bracket.
8. Connect Cables
- Attach the positive cable first, then the negative.
- Tighten the bolts securely.
9. Reinstall Main Battery
- Place the main battery back in position.
- Secure with the hold-down bolts.
- Reconnect the positive cable, then the negative.
10. Test Your Jeep
- Start the vehicle.
- Check for warning lights or error messages.
- Test the Start/Stop system and basic electronics.
Common Mistakes To Avoid
- Disconnecting the positive cable first – Always remove the negative cable first to reduce electrical hazards.
- Forgetting to reset the Start/Stop system – Sometimes the Jeep needs a few minutes or miles to recalibrate after a battery change.
- Choosing the wrong battery size – Double-check the specs before buying.
Comparison: Oem Vs Aftermarket Batteries
Choosing between OEM (original equipment manufacturer) and aftermarket batteries is important. Here’s a quick overview:
| Type | Price Range | Warranty | Performance |
|---|---|---|---|
| OEM | $70-$90 | 12-24 months | Consistent, reliable |
| Aftermarket | $40-$80 | 6-18 months | Varies by brand |
OEM batteries usually last longer, but some aftermarket brands can offer similar performance for less money.
Auxiliary Battery Locations In Wrangler Jl Models
Some Wrangler JL models have slightly different battery placements:
| Model | Auxiliary Battery Location | Access Difficulty |
|---|---|---|
| Sport | Under main battery | Medium |
| Sahara | Beside main battery | Easy |
| Rubicon | Under main battery | Medium |
Always check your model before starting. Sahara models are usually easier to access.
Real-world Example
A 2019 Jeep Wrangler JL owner reported the Start/Stop system error at 38,000 miles. Replacing the auxiliary battery fixed the issue immediately. This is common for Jeeps used in city traffic, where Stop/Start activates often.
Practical Tips For Success
- Wear gloves to avoid acid burns.
- Take photos before removing cables to help with reassembly.
- Dispose of old batteries at recycling centers—never in regular trash.
- Keep radio codes handy, as battery removal can reset some settings.
If unsure, consider watching a trusted video tutorial or consulting your dealer. For more technical details, visit the Jeep Official Website.
Frequently Asked Questions
How Long Does The Auxiliary Battery Last In A Jeep Wrangler Jl?
Most auxiliary batteries last 3-4 years, depending on driving habits and climate. Frequent Stop/Start use can reduce lifespan.
Can I Drive Without Replacing A Failed Auxiliary Battery?
You can drive for a short time, but features like Start/Stop and some electronics may stop working. Prolonged driving can cause electrical issues.
Do I Need To Reset Anything After Replacement?
Usually, the Jeep recalibrates automatically. If warning lights persist, drive for a few miles or check with a dealer for a quick system reset.
Is It Safe To Replace The Auxiliary Battery Myself?
Yes, if you follow safety steps and use proper tools. Always disconnect the negative cable first and wear protective gear.
Where Can I Buy The Correct Auxiliary Battery?
Buy from auto parts stores, Jeep dealerships, or reputable online retailers. Always match the battery specs to your Jeep Wrangler JL.
Replacing the auxiliary battery in your Jeep Wrangler JL is straightforward if you prepare well and follow each step carefully. With the right tools and attention to detail, you’ll restore your Jeep’s reliability and keep all features running smoothly. For most owners, learning this skill saves money and prevents future headaches.
