How do you discharge or charge a capacitor?

L

lucifer

Legacy Member
I have taken out my battery from my car and they told me that before reconnecting i need to discharged the capacitor. How can i do this from the battery directly?
 
^ lol i wish you fixed old tv's or anything else with large capacitors you would learn quick what you said is very false.

Proper way to discharge it is with the proper sized resister across both terminals, but if your in a hurry just short both leads with a screwdriver(holding onto handle)
 
The moment the battery is disconnected, the rest of the car electronics will drain the cap as if it was the battery. It should discharge in no more than a few seconds, a cap doesn't hold shit.

If the cap was disconnected first, then you may want to discharge it using anything that has a resistance like a light bub or resistor, but there's no big reason to discharge it as it only holds 12v you can't get shocked.

When you reconnect the battery you may want to charge the cap first with a resistor, it *may* damage the cap if it's empty when you connect it since it's going to recharge instantly without a resistor.
 
Aleckxss said:
If the cap was disconnected first, then you may want to discharge it using anything that has a resistance like a light bub or resistor, but there's no big reason to discharge it as it only holds 12v you can't get shocked.
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The voltage doesn't do the damage, it's the current. (Which there is way more of in dc applications)
 
Yes, but you won't feel anything at 12V even if you have a zillion amps power source

Your body has a certain resistance, if the voltage goes up, more amps go through it
 
^ Like mentioned 12V will never do damage by electric shock at any amperage to dry skin

What it can do is arc burn you though example being if you hold a ratchet and short it out on both battery terminals there are good chances you will burn your hand.

But mastertee in a way your also right.. voltage is what will give you the effect of pain (think Tazor high voltage, low amperage) but its amperage that will kill you.

By the way im an electrical mechanic and an industrial electrician if anyone has any other questions don't be shy
 
best way is to short it. A cap takes a while to discharge. A big cap might make you wait forever, especially those 1uF +++
 
have you ever connected a light bulb to a cap? a 1F barely lights a flasher bulb for a few seconds

Also, shorting it out "may" damage it.
 
Aleckxss said:
have you ever connected a light bulb to a cap? a 1F barely lights a flasher bulb for a few seconds

Also, shorting it out "may" damage it.
Click to expand...

cause the cap needs time to be charged, your talking abt a 1F cap, that's extremely big ;) that's why HID ballasts requires 20-30secs to have their full colors, operating a 12V 35W ..
 
We are talking about discharging a cap, not charging it

1Farad lights a flasher bulb for seconds and you find that extremely big? That's barely as much energy as a AA battery. Caps are useless for storing lots of energy. Their advantage is that they can discharge instantly if needed: they can provide lots of amps for a small fraction of a second.

I don't understand your link with hid's? My stock HIDs take 5 seconds to reach their color, but in any case that has more to do with the voltage the ballast sends or the filaments' temperature than capacitors?!
 
Capacitors in a car audio system are useful for only 1 thing.. keeping voltage more stable to an amplifier with an unregulated power supply, if your alternator cannot keep up.... that is where they actually can do some good.

When used as a bandaid for dimming lights.. it just hides a symptom..it does not help your battery or alternator in any way....

Also HID's take time to reach full color because the gas inside them takes time to fully heat up... most newer HID kits have a row of capacitors that over-voltage the outputs at start up so you pretty must instantly get full brightness. but for that initial fire-up moment they can pull almost double their "normal" current.
 
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