The largest online repair guide library for every car

About us
Contact support
FAQ
Sign up
Sign in

2018 Civic Si Battery Draining Fast - Alternator or Parasitic Draw?

0

Chris P. · rep 0 · May 25, 1:49 AM · 1 replies · solved · Question

Vehicle: 2018 Honda Civic Si

My 2018 Honda Civic Si has been having battery issues lately. The battery died twice in the last month, and I had to jump-start it. I replaced the battery about 6 months ago, so it's relatively new.

After charging it up, it seems okay for a day or two, but then if it sits for a couple of days, it's dead again. I'm wondering if it's the alternator not charging properly or if there's a parasitic draw somewhere.

I checked the battery terminals, and they seem clean and tight. No warning lights are on while driving, but it's really frustrating to come out to a dead car. Any ideas on how to diagnose this myself before taking it to a shop?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 1:49 AM

0

ClearTheCode admin answer:

It sounds like you're dealing with either a charging system fault or a parasitic draw. Here's how to approach diagnosing it:

  1. Test the Alternator:

    • With the car running, use a multimeter to check the voltage across the battery terminals. It should read between 13.5 and 14.5 volts. If it's significantly lower (e.g., below 13V), your alternator might not be charging the battery effectively.
    • Turn on all accessories (headlights, AC, radio) and re-check the voltage. It should remain above 13V. A significant drop indicates a weak alternator.

  2. Check for Parasitic Draw:

    • Ensure the car is off, all doors are closed, and interior lights are off. Wait about 15-20 minutes for all modules to 'go to sleep'.
    • Disconnect the negative battery cable. Connect a multimeter in series between the negative battery post and the disconnected negative battery cable (set to amperage, usually 10A or 20A range).
    • A normal draw is typically under 50 milliamps (0.05 amps). If you see a significantly higher reading (e.g., 200mA+), you have a parasitic draw.
    • To find the source, start pulling fuses one by one while watching the multimeter. When the amperage drops significantly, you've found the circuit with the draw. Common culprits include aftermarket accessories, faulty relays, or modules not shutting down properly.

When to See a Shop: If you're uncomfortable performing these electrical tests, or if you identify a parasitic draw but can't pinpoint the exact component, it's best to consult a professional mechanic. They have specialized tools and diagnostic equipment to quickly identify and resolve complex electrical issues. A shop can also perform a more thorough load test on your battery and alternator to ensure they are functioning optimally under various conditions.

Menu

Help & account