🔧 Flex - Battery Replacement

You’ll remove the old 12V battery from the engine bay and install a new one with the correct size and terminals. Doing it the right way prevents electrical glitches and helps your Flex’s charging system “learn” the new battery.

Difficulty Level: Beginner | Estimated Time: 0.5-1.0 hours

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⚠️ Safety & Precautions

• ⚠️ Wear eye protection and gloves; batteries can leak acid and spark.
• ⚠️ Key off, remove key/fob, and wait 5 minutes before disconnecting (lets modules go to sleep).
• ⚠️ Always disconnect the negative (-) cable first and reconnect it last.
• ⚠️ Do not let a tool touch both battery terminals (or terminal to body metal) at the same time.
• ⚠️ No airbag/ADAS work is required, but you may lose radio presets and clock settings.

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🔧 Required Tools

You'll need the following tools for this repair:

• 8mm socket
• 10mm socket
• 1/4" drive ratchet
• 6" extension (1/4" drive)
• Torque wrench (inch-pound)
• Battery terminal puller (specialty)
• Battery terminal cleaning brush
• Shop rags
• Nitrile gloves
• Safety glasses

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• 12V battery (correct group size for your Flex) - Qty: 1
• Battery terminal anti-corrosion pads - Qty: 2
• Battery terminal protectant spray - Qty: 1

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📋 Before You Begin

• Park on level ground, shift to Park, and set the parking brake.
• Turn everything off (lights, HVAC, radio). Remove the key/fob from the vehicle.
• Open the hood and keep it securely supported.
• Tip: Take a photo of cable routing first.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Locate the battery and remove any covers

• Open the hood and locate the battery at the front of the engine bay.
• If there’s a protective cover, remove it using a 10mm socket (fasteners vary by cover style).

Step 2: Disconnect the negative (-) battery cable

• Use an 8mm socket to loosen the negative terminal clamp nut (marked “-”, usually black cable).
• Twist and lift the clamp off the battery post. If it’s stuck, use a battery terminal puller (specialty) (this tool lifts the clamp without damaging it).
• Tuck the negative cable aside so it cannot spring back and touch the terminal.
• Torque to 6 Nm (53 in-lbs) when tightening later.

Step 3: Disconnect the positive (+) battery cable

• Use an 8mm socket to loosen the positive terminal clamp nut (marked “+”, usually red cover).
• Remove the clamp from the post and move it aside carefully.
• Torque to 6 Nm (53 in-lbs) when tightening later.

Step 4: Remove the battery hold-down

• At the base of the battery, remove the hold-down bolt using a 10mm socket and 6" extension (1/4" drive).
• Lift out the hold-down bracket.
• Torque to 10 Nm (89 in-lbs) during re-install.

Step 5: Remove the old battery

• Lift the battery straight up and out. Batteries are heavy—use good posture and keep it close to your body.
• Set it on the ground upright (don’t tip it).

Step 6: Clean and prep the terminals

• Use a battery terminal cleaning brush to clean the inside of the cable clamps until shiny metal is visible.
• Wipe with shop rags.
• Install battery terminal anti-corrosion pads on the new battery posts.

Step 7: Install the new battery

• Place the new battery into the tray with terminals oriented the same way as the original.
• Reinstall the hold-down bracket and bolt using a 10mm socket.
• Torque to 10 Nm (89 in-lbs).

Step 8: Reconnect the positive (+) cable, then the negative (-) cable

• Install the positive clamp first and tighten using an 8mm socket.
• Torque to 6 Nm (53 in-lbs).
• Install the negative clamp last and tighten using an 8mm socket.
• Torque to 6 Nm (53 in-lbs).
• Spray terminals lightly with battery terminal protectant spray.

Step 9: Reset the Battery Monitoring System (BMS)

• Your Flex uses a battery monitoring strategy; resetting helps charging behavior match the new battery.
• Manual reset (no scan tool):
• Turn ignition to ON (engine off).
• Within 10 seconds: pull the high-beam stalk to flash high beams 5 times, then press and release the brake pedal 3 times.
• Watch for the battery/charging indicator to flash (confirmation varies by cluster).
• Scan-tool reset: Use a capable scan tool and run BMS Reset / Battery Replacement for the BCM (preferred if available).
• Tip: If it doesn’t confirm, repeat calmly.

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✅ After Repair

• Start the engine and confirm normal cranking.
• Confirm there are no warning lights related to charging/battery after a short drive.
• Reset clock and radio presets as needed.
• Make sure the battery is secure (it should not move by hand).

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💰 DIY vs Shop Cost

Shop Cost: $220-$450 (parts + labor)

DIY Cost: $140-$280 (parts only)

You Save: $80-$170 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 0.5-1.0 hours.

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🎯 Ready to get started?

HowToo makes it easy: same-day/2-day shipping on every part, plus all the tools and specialty tools you need! Check out the parts and tools sections below to add everything to your cart.