Check my battery
Dead Battery or Alternator? Checker
Answer a few quick questions about what your car is doing, and we'll point you to the most likely cause and what to check next.
Last updated October 2026. By the editorial team.
What is your car doing?
How to use this tool
1. Notice the symptom
What does the car do when you try to start it?
2. Pick the closest match
Choose the symptom that fits best.
3. Read the likely cause
Battery, charging system, starter or connection.
4. Follow the next steps
Safe checks and links to the voltage checker.
Why Battery and Alternator Faults Look Alike
The battery starts the car and the alternator recharges it while you drive. When either fails, you end up with a flat battery, which is why they get confused. This page stays focused on the battery side: what to check, how to rule the battery in or out, and when replacement makes sense. We do not cover full alternator repair.
Next, confirm with numbers using the battery voltage checker. If the battery is the problem, see how much a car battery replacement costs, and learn how to jump-start a car safely to get moving first.
Frequently asked questions
How can I tell a bad battery from a bad alternator?
If the car starts with a jump but dies soon after, suspect the alternator. If it will not hold a charge overnight but runs fine once started, suspect the battery. A voltage test with the engine running separates them.
Is this a diagnosis?
No. It points to the most likely cause so you know what to check first. A shop test is the only way to be sure.
Related tools and guides
Battery voltage checker
Confirm with a multimeter.
Learn moreHow to jump-start a car
Do it safely.
Learn moreReplacement cost calculator
If the battery is the cause.
Learn more