Is my car battery dead or is it the alternator?
When a car battery repeatedly dies after a couple of days and requires a jump-start, it is hard to tell whether the battery itself is failing or if there is an electrical problem with the alternator. This uncertainty leaves non-car people stranded and unable to reliably start or move their vehicles.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
Found another way around this?
Share your steps and trade-offs so fellow engineers don't have to reinvent the wheel. No account required.
- 1Trickle charging the battery, testing voltage while driving with a tool, getting components bench tested at an auto parts store, and jump-starting the vehicle.Did this help you?
- 2Visiting a starter/alternator shop to find a replacement or upgrading to an internally regulated version.Did this help you?
- 3Asking mechanics online by posting audio or video clips of the engine startingDid this help you?
- 4Taking the alternator to an auto parts store for free testingDid this help you?
- 5Testing the alternator on the vehicle with the car runningDid this help you?
- 6opening the bonnet and checking the battery with a multimeterDid this help you?
- 7Using a wire brush to scuff up the surfaceDid this help you?
- 8Spraying cleaner on them and applying protectorDid this help you?
- 9Using a terminal cap if they can wiggleDid this help you?
- 10Idling the car for half an hour with the heat and lights running to see if the battery dies.Did this help you?
- 11Watching the dashboard voltmeter to verify the voltage goes up when the car is turned on.Did this help you?
- 12Turning off all electrical draws like lights and the radio if the voltage gauge drops.Did this help you?
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“I didn't know that. Going to autozone now”source ↗
“Just going crazy. Not sure if I diagnosed it right. Just want some second opinions before I test drive the new one and I get stranded.”source ↗
“Having an issue that may be electrical in nature, anyone know what this alternator is? It is on a 1951 flathead ford 8ba and the battery is slowly dying.”source ↗
“Does it sound like it's over spinning or grinding/whirring?”source ↗
“Were it the alternator that were also the issue, would it even still start, let alone run with all of the electrics like heat, lights, etc running fine?”source ↗
“I don't want to drive anywhere to test the alternator, at least currently.”source ↗
“I've had a few alternators die on me mid drive. I've never made it more than 20-25 miles, 20-30 minutes of the car running before it was too dead to stay on.”source ↗
“Are my battery terminals bad?”source ↗
“Went to start the car 2 days later, battery dead again. Had to jump it to move it. I am not a car person. Any idea which is the issue?”source ↗
“Car wasn’t turning over and having electrical problems until I cleaned them”source ↗
“Is there a simple way to detect an alternator/charging failure from inside the car?”source ↗
“My dashboard doesn't show a charging warning.”source ↗
“I also hate opening the bonnet and checking the battery with a multimeter any diy or readymade cheap and quick solutions?”source ↗
Where this came up
People with this problem also raised
- 27Car battery keeps dying even after replacing battery and alternator
- 4How to tell if a car part is actually damaged
- 3Why does a new car battery test bad-replace?
- 2Do I actually need to register a new car battery?
- 7Car battery leaking acid with no warning lights
- 2Should I replace corroded battery cables or just the terminals?