Symptoms
- Needed a jump more than once in the last few weeks
- Battery seems to drain even after driving
- Slow cranking before the car finally starts
- Dashboard battery light comes on while driving
Likely causes
- CommonBattery reaching end of lifeMost car batteries last 3–5 years; older batteries lose the ability to hold a charge.
- CommonParasitic drain from a light or accessoryA trunk light, glovebox light, or aftermarket accessory left partially on can drain a battery overnight.
- PossibleFailing alternator not recharging the battery while drivingIf the alternator underperforms, the battery never gets fully topped back up.
- PossibleLoose or corroded terminal reducing charging efficiencyPoor contact can prevent the battery from charging properly even if the alternator is fine.
What to do
- Have the battery load-tested at an auto parts store or shop; most do this for free and it will show if it's simply worn out.
- Check for anything left on overnight, like interior lights, phone chargers, or aftermarket electronics.
- Have the charging system (alternator output) tested at the same time as the battery, since a good battery paired with a bad alternator will still keep dying.
- Inspect and clean battery terminals for corrosion or looseness, which can mimic charging problems.
- If the battery is more than 3–5 years old and tests weak, replace it rather than continuing to jump-start it.
- Keep a jump starter pack in the trunk in the meantime so you're not stranded while diagnosing the cause.
Tools and parts
- Multimeter (optional)
Replacement car battery, correct group sizeSearch: “car battery group size for [your car year make model]”
When to call a pro
If the battery and terminals test fine but the car still won't hold a charge, have the alternator and charging system professionally tested.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.