Fixing Your Challenger's Electrical Warnings: Battery & Alternator Guide

How to Fix Battery Replacement

For 2020 Dodge Challenger owners, a failing battery can trigger a cascade of confusing electrical warnings and leave you stranded. While replacing the battery itself is often the solution, proper diagnosis is key to ensure you're fixing the root cause and not just a symptom. As one owner shared after experiencing a series of alarming warnings: "Then the forward collision warning and the power steering warning lights came on and it refuses to shut off. I did have to jump the battery a couple days ago." — AlphaDogGaming2. This guide will walk you through the symptoms, diagnosis, and replacement process based on real owner experiences.

Symptoms

Owners report a variety of symptoms that point toward a weak or failing battery, often mistaken for more complex electrical gremlins. The most common initial sign is difficulty starting the car or needing a jump-start. However, the advanced electronics in this vehicle mean a low battery voltage can cause seemingly unrelated systems to malfunction.

You may experience a cluster of warning lights illuminating on your dashboard. As documented by an owner, these can include the forward collision warning and electronic power steering warnings, which can be startling and suggest major system failures. The vehicle may also refuse to shut down properly or exhibit strange behavior in accessory mode, like power seats or infotainment screens not functioning. "I was on my lunch break and had it on Acc when I tried to move the seat up and it wouldn't work." — AlphaDogGaming2.

Other symptoms include general electrical sluggishness. You might notice the interior lights dimming, the radio resetting, or windows moving slower than usual. In severe cases, the car may not recognize the key fob or have issues with the security system. It's crucial to recognize these as potential battery issues before investigating more expensive components like alternators or control modules.

Most Likely Cause

The primary cause of battery failure and related electrical issues, as identified by owners, is a compromised charging system, specifically an alternator that is not properly maintaining the battery's charge. A healthy alternator should recharge the battery while the engine runs. If it fails, it allows the battery to be depleted by the vehicle's constant electrical draws, even during short drives.

This failure mode is critical to understand. A battery can test as "bad" simply because it has been deeply discharged and damaged by an underperforming alternator. As one owner wisely advised for diagnosis: "Check voltage with engine off and with engine running. If voltage is below 12-13 with engine off and with engine running, it's likely a bad alternator that's allowed your battery to run low. Battery may still be ok" — Hop-Dizzle-Drizzle. Therefore, the most likely cause of recurring battery problems is not the battery itself, but an alternator that is no longer outputting sufficient voltage (typically 13.5-14.5 volts when running).

How to Diagnose

Accurate diagnosis prevents you from replacing a good battery or missing a failing alternator. You will need a digital multimeter, which is an inexpensive and essential tool for any DIYer.

First, perform a static voltage test. With the vehicle completely off and all doors closed for at least an hour, connect the multimeter's red lead to the battery's positive terminal and the black lead to the negative terminal. A healthy, fully charged battery should read between 12.4 and 12.7 volts. Anything below 12.2 volts indicates a significantly discharged state and the battery may be failing or have been drained by a parasitic draw or bad alternator.

Next, perform a charging system test. Have a helper start the engine and let it idle. Reconnect the multimeter to the battery terminals. A functioning alternator should now show a voltage between 13.5 and 14.5 volts. If the voltage is below 13.5 volts (or is the same as your static test), your alternator is not charging properly. If the voltage is above 14.8 volts, the alternator is overcharging and will cook the battery. As Hop-Dizzle-Drizzle's advice confirms, this two-step test is the cornerstone of diagnosis: checking both states tells you if the battery is bad, the alternator is bad, or both.

Finally, if the alternator tests good but the battery continues to die, you may have a parasitic draw. This is when a component (like a trunk light, infotainment screen, or aftermarket accessory) stays on and drains the battery overnight. Diagnosing this requires more advanced use of a multimeter to measure amperage draw with the car asleep and is often best left to a professional if you're not comfortable.

Step-by-Step Fix

Replacing the battery in a 2020 Challenger is straightforward, but location and electrical preservation are key. The battery is located in the trunk on the driver's side, behind a trim panel.

Step 1: Preparation. Park on a level surface, set the parking brake, and ensure the vehicle is off. Open the trunk and remove any cargo from the driver's side. Gather your new battery, basic socket set (typically 10mm), and your multimeter.

Step 2: Access the Battery. You'll need to remove the trunk side trim panel. This usually involves removing a few plastic push-pins or screws. Be gentle to avoid breaking the clips. Once the panel is off, you'll see the battery secured in a tray. "I was super confused. I just never looked under there before until I had to replace my battery." — MSG_Ximnis. This surprise is common for first-timers.

Step 3: Disconnect the Battery. CRITICAL: NEGATIVE FIRST. Using your socket, loosen and remove the nut on the negative (-) terminal clamp. Carefully lift the clamp off the terminal and tuck the cable away so it cannot accidentally touch the terminal. Repeat the process for the positive (+) terminal clamp.

Step 4: Remove the Old Battery. There is usually a hold-down bracket securing the battery. Remove the bolt(s) for this bracket and set it aside. The battery can be heavy (30-50 lbs), so lift with your legs. Carefully lift the battery straight up and out of the tray.

Step 5: Install the New Battery. Place the new battery into the tray in the same orientation. Reinstall the hold-down bracket and tighten securely. This prevents vibration damage.

Step 6: Reconnect the Battery. CRITICAL: POSITIVE FIRST. Connect the positive (+) cable clamp to the positive terminal and tighten the nut securely. Then, connect the negative (-) cable clamp to the negative terminal and tighten. A light coating of dielectric grease on the terminals can help prevent future corrosion.

Step 7: Reset and Test. Close the trunk. Enter the vehicle and start the engine. You will likely need to reset your clock, radio presets, and power window auto-up/down features (roll each window all the way down and then all the way up, holding the switch for a second at each extreme). Use your multimeter again to verify the alternator is charging (13.5-14.5V with engine running).

Parts and Tools Needed

• Battery: A Group 94R battery is the standard size for most 2020 Challengers. Opting for an AGM (Absorbent Glass Mat) battery is highly recommended for its longer life, better vibration resistance, and superior performance. Mopar part numbers vary, but a common replacement is 05092536AA (AGM). Always double-check your specific trim level (e.g., Hemi models may have different requirements).
• Basic Socket Set & Wrenches: A 10mm socket and ratchet are most common for terminal clamps and hold-downs. A small adjustable wrench can be a backup.
• Digital Multimeter: Essential for pre- and post-installation testing. A basic model from any hardware store is sufficient.
• Dielectric Grease: A small tube (often included with premium batteries) to coat terminals and prevent corrosion.
• Battery Terminal Cleaner/Brush: Useful if you encounter corrosion on the cable clamps.
• Trim Removal Tool (Optional): Helpful for prying off the trunk side panel without damaging it.

Real Owner Costs

Costs can vary widely based on the battery quality, whether you DIY, and if other issues are discovered.

• DIY Battery Replacement: The cost is primarily the battery itself. A standard flooded lead-acid Group 94R battery can cost $150-$220. A premium AGM battery, which is a better long-term investment, typically runs $250-$350. Your only other cost is for basic tools if you don't already own them. Total DIY cost: $150 - $350.

• Professional Battery Replacement (Shop/Dealer): This adds significant labor costs. Dealerships and repair shops will charge 0.5 to 1.0 hour of labor, which can range from $75 to $200 per hour depending on location. A dealership will almost certainly use a Mopar AGM battery at a premium price. As one owner's experience with body damage shows, dealer repair invoices can be high: "I paid a $1000 deductible but the dealer's service department presented a $9K invoice to the insurance company for the repairs..." — MetroGunslinger. While for a different repair, it illustrates dealer labor rates. Expect a professional battery replacement to total $400 - $600+ at a dealer, and slightly less at an independent shop.

• Additional Cost - Alternator: If diagnosis reveals a failed alternator, part costs can range from $250 for a remanufactured unit to $500+ for a new OEM part. Labor for alternator replacement is more intensive (2-3 hours), potentially adding $300-$600 in labor, making a full alternator replacement job $550 - $1,100+.

Prevention

Preventing premature battery failure involves managing the charging system and mitigating drain during storage.

The single best practice for owners who don't drive daily or plan to store the vehicle is to use a battery maintainer (tender). This is a small, smart charger that plugs into a wall outlet and connects to your battery to keep it at optimal charge without overcharging. "Don't need to remove the battery, you can use a battery tender to keep the car's electrics happy and the battery is still charged." — WoolyFox. For long-term storage, this is considered essential.

For extended storage, combine this with other preparation steps. "Fill the tank all the way up with non-ethanol premium then put stabilizer in it air the tires up to 40 psi to help with flat spots change the oil before storage I put damp rid inside the car to control moisture also under it to keep moisture off cover it if you can..." — mattfromaalta. A clean car also prevents pests: "Wash it and clean it inside and out really well. Any food left in the car will rot and attract rodents and make the car disgusting when you open the doors on return." — WoolyFox.

For daily drivers, have your charging system (battery and alternator output) tested annually, especially before winter. Avoid short trips that don't allow the battery to recharge fully, and minimize using accessories (radio, lights, seat warmers) when the engine is not running.

What Owners Say

Real experiences from DODGE owners:

Owner Experiences

"Wash it and clean it inside and out really well. Any food left in the car will rot and attract rodents and make the car disgusting when you open the doors on return." — WoolyFox (source)

"Don't need to remove the battery, you can use a battery tender to keep the car's electrics happy and the battery is still charged. Wash it and clean it inside and out really well." — WoolyFox (source)

"Check voltage with engine off and with engine running. If voltage is below 12-13 with engine off and with engine running, it's likely a bad alternator that's allowed your battery to run low." — Hop-Dizzle-Drizzle (source)

Lessons Learned

⚠️ "Then the forward collision warning and the power steering warning lights came on and it refuses to shut off. I did have to jump the battery a couple days ago." — AlphaDogGaming2 (source)

⚠️ "I was on my lunch break and had it on Acc when I tried to move the seat up and it wouldn't work. Then the forward collision warning and the power steering warning lights came on and it refuses to shut off." — AlphaDogGaming2 (source)

Real Repair Costs

"I paid a $1000 deductible but the dealer's service department presented a $9K invoice to the insurance company for the repairs (probably excessive but they were also the most qualified to make the repairs)." — MetroGunslinger (source)

FAQ

Q: How long does it take to replace the battery? A: For a first-time DIYer, allowing time to locate the battery in the trunk and carefully remove the trim panel, the job should take 30 to 45 minutes. If you're familiar with the process, it can be done in 15-20 minutes. A professional mechanic at a shop can typically complete it in under 30 minutes of billed labor time.

Q: Can I drive with a failing battery or alternator warning lights? A: It is not advisable. While you might be able to drive for a short while on battery power alone, once the battery's reserve is depleted, the vehicle will stall as all electronics fail. The sudden loss of power steering and braking assist (which are electronically controlled in many modern cars) creates a dangerous driving situation. If warning lights cluster as described by owners, you should drive directly to a repair facility or prepare to be towed.

Q: Is this a common issue on the 2020 Challenger? A: Based on owner discussions, electrical issues stemming from battery and charging system problems are a recurring topic. The complexity of the vehicle's electrical architecture makes it sensitive to low voltage, which manifests in various warning lights. The battery's location in the trunk is also a point of confusion, leading to questions. It's a common enough maintenance item that owners should be familiar with the diagnosis process.

Q: DIY vs mechanic - what's recommended? A: The actual battery replacement is very DIY-friendly if you are comfortable with basic hand tools and following safety procedures (disconnecting negative first). The crucial part is the diagnosis. If you can confidently use a multimeter to test battery and alternator voltage as outlined, you can save significant money. If the symptoms are intermittent or you suspect a parasitic draw, or if you are not tool-inclined, taking it to a trusted mechanic for a definitive diagnosis is the recommended path. They can perform a load test on the battery and a full charging system test.

Q: Do I need to reprogram anything after a battery change? A: Yes, you will need to reset some features. The clock and radio presets will be lost. More importantly, the power window "auto-up" and "auto-down" functions often need to be re-initialized. This usually involves rolling each window all the way down and then holding the switch in the up position for a few seconds after it closes. Your owner's manual has the specific procedure. Some higher-end audio or security settings may also need adjustment.

Q: Will a battery tender really prevent battery death during storage? A: Absolutely. Owner experiences strongly endorse this. A quality battery maintainer provides a small, regulated trickle charge that counteracts the vehicle's natural parasitic draw (from systems like the keyless entry computer). It keeps the battery at a full state of charge, preventing the sulfation that occurs in deeply discharged batteries and is a primary cause of failure. It's a small investment that can double the life of your battery if you store the car seasonally.