What’s Causing Your Car Battery to Drain?

by | Jan 31, 2024 | Towing Service

A dead battery when you least expect it is beyond frustrating. But don’t despair quite yet—identifying the culprit can get you back on the road. By methodically looking at potential battery drainers, you can pinpoint issues and make fixes.

Rule Out a Faulty Battery

Before assuming a parasitic drain, check battery date codes. Most last 3-5 years. If yours is 5+ years old, replacing it may solve everything. Use a voltmeter to test its charge after a full night’s rest. If still low, it’s likely time for a new battery.

Consider Your Driving Habits

Frequent short trips and stop-and-go traffic never fully recharges batteries. Their chemical reactions maximize charge via extended highway speeds. If possible, take your car on 20+ minute trips to prevent sulphation buildup on plates from undercharging.

Watch For Warning Lights

Battery/charging system warning lights indicate trouble. Don’t ignore them! Take your car to a shop to test for defective alternators or loose terminals right away. Catching minor issues now prevents being stranded later.

Use a Voltmeter to Find Parasitic Drains

If the battery and alternator test fine, a parasitic current drain is likely. Turn off all electronics in your parked car. Carefully disconnect the negative battery cable and set a voltmeter to its 20V DC scale. Attach the voltmeter leads across the battery posts. Any measurement above 50 milliamps indicates a problem.

Track Down the Source

Now systematically pull fuses while watching voltmeter readings. When drain drops significantly upon pulling a certain fuse, you’ve found the circuit containing the parasitic drain. Inspect connections and wiring along that circuit (stereo, security system, computer modules, etc.) to locate and fix breaches allowing current to trickle out. Need help with this? Check with an auto mechanic in Fitchburg WI.

Prevention Is Ideal

Once everything checks out fine, get in habits to avoid future battery drain headaches:

  • Turn electronics/accessories off fully when parking
  • Fix minor electrical issues quickly
  • Clean battery terminals monthly
  • Let car run long enough to fully charge battery

With some diligence and voltage testing, you can figure out what’s prematurely sapping your battery capacity. A bit of prevention and early troubleshooting keeps your car battery in top shape for reliable starts every time.

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