Why are capacitors considered more dangerous than batteries in automotive electronics?

It's a simple matter of courtesy and protection. If for any reason your car needs to be worked on (battery removed), a notification that a possible voltage may still be present on the hot wire, even when disconnected from the battery, may save some guy from banging his head on the hood when sparks fly for 'some unknown reason'.

Some people forget they have such a device installed.

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As for the other answers - noobs. If you read through the vast questions that KaeZoo has answered, you'll find he's not a greenhorn at this.

The answer is simple once you understand a few things.

First Capacitors have many general uses. Power factor correction and power storage are 2 of them. For power storage which I believe you are more concerned with given your reference to batteries, they serve quite well. However they are MUCH more dangerous than batteries.

Reasons why:

1. As opposed to a battery, a capacitor can discharge its ENTIRE charge in a very small fraction of a second. Batteries can not. This makes the total energy involved in a short circuit much higher with a capacitor than your typical battery.

2. Capacitors can explode. Yes, explode not unlike a grenade. This can happen when you have a direct short on a capacitor or some other conditions like wiring a charge capacitor backwards and applying voltage.

3. Given #1 and 2 above do you need more?

I hope this answers you questions.

Fear of the unknown. I guess the horror stories of caps exploding scare people. The first time I installed one I was nervous. I had always heard you have to get them charged before you install them, and you had to discharge them before storing them. I had this idea that they very powerful and unstable.

Everyone thinks a capacitor will prevent your lights from dimming and make your system hit twice as hard. If this were the case, a cap would be very dangerous.

I read a few years ago that a man died while washing his car simply by touching the battery with his elbow. He was detailing the engine, and his wet elbow touched the positive post while his chest was against the body of the car. It only takes a few milliamps to stop the heart.

I have never heard of caps killing anyone. Matter of fact, I have leaned across the posts while covered in sweat in the trunk of a car once.. I got a slight tingle, but that's about it.

Although you can't be electrocuted by twelve volts, a capacitor with a large charge could hold enough energy to cause burns or start a fire. Also, electrolytics can explode if the polarity is reversed. In the case of televisions, there is a high voltage supply for the CRT, and the capacitor there can deliver a nasty jolt.

I think that the idea of dangerous capacitors comes from a little from the past. At the beginning the first capacitors were really big and heavy,they have oil inside as dielectric material and other toxic chemicals that were harmful to humans. That's the case for TVs. I remember my professor of physics saying be very careful at working with TV circuitry since they work with very high voltages and and so the capacitors inside had a high voltage too, repairing technicians had to be very careful to do no disturbed the caps inside, i guess that the myth continued with time.

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culkplittle...

did you know that with only 10mA your heart can be stopped.??

that is tricky but the only reason i could think is because capacitors stored full of highly charged electricity as opposed to a battery that is usually a trickle style charge.

once your car is started you engine does all the work and the battery is used sparingly. the capacitor always has power running through it. and yes the shocks from a fully charged capacitor can cause it to explode if it is not depleted before reinstalation or reinstalled right

A capacitor can still hold a charge even after the battery has been disconnected, and deliver it with one hell of a kick if you're not careful

Primarily it has to do with the charging and discharging of caps. Failure to heed proper polarity will almost surely result in capacitor failure, even with a source voltage as low as 6 volts. When electrolytic capacitors fail, they typically explode, spewing caustic chemicals and emitting foul odors. Please, try to avoid this!

Capacitors CAN store much more energy than your cars battery. Many audio circuits have voltages nearing 300vdc! Not much current but plenty of voltage! They can be particularly dangerous because the average Joe doesn't realize the potential is there. Most folks assume that because a device is disconnected from it's power source that it is "dead". Be careful! ;-)=