can car battery be dead and radio still work

[DiMiguel]

Yes, a car battery can be dead enough to prevent the engine from starting while still having just enough power to run the radio and other low-power electronics like interior lights. This situation is surprisingly common and occurs because of the vastly different electrical demands of various components in your car.

The primary reason is the difference in amperage (current) required. Starting the engine requires a massive, brief burst of power—often 150 to 300 amps—to turn the starter motor. A weak or dying battery simply cannot supply this "cranking amps" demand. In contrast, a car radio only draws about 5 to 10 amps. A battery that is nearly depleted might still hold enough charge to power small electronics but falls short when faced with the enormous load of the starter.

Component	Approximate Power Requirement (Amps)	Battery State Required
Interior Dome Light	2 - 5 A	Very Low
Car Radio	5 - 10 A	Low
Headlights	10 - 15 A (per pair)	Moderate
Windshield Wipers	5 - 10 A	Moderate
Starter Motor	150 - 300 A	High (Full Charge)

This state often indicates a battery that is failing due to age, has a weak cell, or has been drained by something left on (like a dome light) for an extended period. It's a clear warning sign. If you experience this, using jumper cables or a portable jump starter is the typical solution. However, repeatedly draining a battery this low can significantly shorten its overall lifespan. After jump-starting, it's wise to drive the car for at least 20-30 minutes to allow the alternator to recharge the battery properly. If the battery is more than 3-4 years old, this event might mean it's time for a replacement.

[Paige]

Absolutely. Think of the battery like a water tank. The starter needs a huge bucket of water all at once. A weak battery might only have a few cups left—enough for the radio's tiny sip, but not nearly enough to fill the starter's bucket. The lights and radio are the first things to get power, and they're the last to go out when the battery's dying. It's a classic sign you need a jump start.

[SanGia]

I just went through this last month. My car's radio and dashboard lights came on like normal, but when I turned the key, all I heard was a rapid clicking sound—the engine wouldn't turn over. It turned out my battery was five years old and just couldn't deliver the big jolt needed to start the car anymore. A quick jump from a neighbor got me going, but I had to replace the battery that weekend. It’s a frustrating but clear signal your battery is on its last legs.

[DelBenjamin]

From a technical standpoint, this is a clear demonstration of voltage sag under load. A "dead" battery in this context isn't at 0 volts; it might still show 11-12 volts when measured with a multimeter with no load. However, when you engage the starter, the demand for current causes the voltage to plummet drastically to a level where the engine control unit and ignition system can't function. The radio, with its minimal draw, doesn't cause this significant voltage drop, so it continues to operate until the battery is completely exhausted.