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2018 Sorento EX - Battery keeps draining, suspect alternator or parasitic draw

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Chris P. · rep 0 · May 22, 3:08 AM · 1 replies · solved · Question

Vehicle: 2018 Kia Sorento EX

Hey everyone,

I've got a 2018 Kia Sorento EX with about 75,000 miles, and I'm having a persistent issue with the battery draining. It's happened a few times now where I'll go to start it in the morning, and it's completely dead. I've had the battery tested, and it seems fine, but it just won't hold a charge.

I'm wondering if it could be the alternator not charging properly, or maybe a parasitic draw somewhere. I've noticed the headlights seem a little dim sometimes when it's running. Has anyone else experienced this with their Sorento? Any tips on how to diagnose it myself before taking it to a shop?

I've tried checking the fuses, but nothing obvious seems blown. It's really frustrating to wake up to a dead car!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 3:08 AM

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ClearTheCode admin answer:

Battery draining issues in a 2018 Kia Sorento EX can stem from several electrical problems. It's crucial to diagnose this accurately to avoid further damage or inconvenience.

Possible Causes:

  1. Failing Alternator: The most common cause of a battery not holding a charge is a faulty alternator. It's responsible for recharging the battery while the engine runs and powering the electrical system. If it's not producing enough voltage (typically 13.5-14.5V), the battery will slowly discharge.
  2. Parasitic Draw: This occurs when an electrical component continues to draw power from the battery even when the vehicle is turned off. Common culprits include:
    • Aftermarket accessories (stereo, alarm systems)
    • Stuck relays
    • Faulty body control modules (BCM)
    • Glove box or trunk lights staying on
    • Faulty infotainment system components
  3. Weak or Failing Battery: Even if a battery tests 'good' under a basic load test, it might have internal issues preventing it from holding a charge effectively, especially if it's several years old.
  4. Loose or Corroded Battery Terminals: Poor connections can prevent proper charging and lead to intermittent power issues.

Diagnostics & Troubleshooting Steps:

  1. Check Battery Terminals: Ensure they are clean, tight, and free of corrosion.
  2. Test Alternator Output: With the engine running, use a multimeter to measure the voltage across the battery terminals. It should read between 13.5V and 14.5V. If it's lower, the alternator might be failing. A common OBD-II code for low system voltage is P0562.
  3. Perform a Parasitic Draw Test:
    • Ensure all doors are closed, lights are off, and the key is out of the ignition.
    • Disconnect the negative battery cable.
    • Connect a multimeter in series between the negative battery post and the negative battery cable (set to amperage, usually 10A or 20A range).
    • Wait 15-30 minutes for all modules to 'sleep'.
    • A normal draw is typically under 50mA (0.05A). If it's significantly higher, start pulling fuses one by one until the draw drops, indicating the circuit with the fault.
  4. Professional Battery Test: Have the battery professionally tested with a conductance tester, which can better assess its internal health.

When to See a Shop:

If you're uncomfortable performing these electrical tests, or if your multimeter readings indicate an issue (low alternator output, high parasitic draw) that you can't pinpoint, it's best to take your 2018 Kia Sorento EX to a qualified mechanic. They have specialized tools and diagnostic equipment to accurately identify the root cause, especially for complex parasitic draws or internal module failures. Ignoring a persistent battery drain can leave you stranded and potentially damage other electrical components.

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