VWVortex.com - How long does a capacitor hold a charge for?

# Thread: How long does a capacitor hold a charge for?

1. I have heard a rumor that the charge a capacitor holds can be lethal. How long does it hold a charge for, and is it lethal?
Thanks
[IMG]http://*****************.com/smile/emthup.gif[/IMG]

2. Just like a battery, a long time. And Yes, if hit in the right spot, it could be lethal.

3. Lethal is walking into 5" wide X 10" long x 12" high with opposing walls covered completely with copper, then being told your standing in the capacitor.
As for how long will a cap hold it's charge, it really depends on how much leakage current is developed inside the cap. The larger the electrolytic, the larger the leakage current. A cap that has a higher working voltage than the applied voltage the longer it will hold a charge, and help reduce the leakage current. Although it won't reduce it drastically.

Modified by Non_Affiliated at 7:09 PM 1-23-2007

4. ok, a friend of mine has one he had hooked up to his system in his old, but now he is afraid to touch it and has it securely stored away. I guess his fears were warranted. Thanks!

5.  Quote, originally posted by pickles and mayo » ok, a friend of mine has one he had hooked up to his system in his old, but now he is afraid to touch it and has it securely stored away. I guess his fears were warranted. Thanks!

Stored away? Like not in the car anymore?
Anyway, a cap isn't going to hurt you. If the cap is out of the car discharge it with a test light.

6.  Quote, originally posted by midwestbass » Anyway, a cap isn't going to hurt you.

yes the hell it will if you dont discharge it properly.
from a tesla coil site
"Capacitors can also build up a residual charge from electrostatic sources.
Capacitors have been known to accumulate a charge from various sources such as static electricity and electric fields. IF YOU STORE A CAPACITOR, STORE IT WITH A WIRE ACROSS THE TERMINALS. (MAKE SURE YOU DISCHARGE THE CAPACITOR BEFORE PUTTING THE WIRE ON!!!)
Capacitors can "regain" charge from dielectric "memory". The dielectric in a capacitor is put under electrical stress during use. During operation, this stress may cause the molecules in the dielectric to orient themselves in such a manner that they store this charge in their structure. The charge remains after the capacitor has been discharged. Later the molecules return to their original states and the charge that they "captured" ends up on the plates of the capacitor. This charge is then available to shock you.
"

7.  Quote, originally posted by afinley » yes the hell it will if you dont discharge it properly. from a tesla coil site "Capacitors can also build up a residual charge from electrostatic sources. Capacitors have been known to accumulate a charge from various sources such as static electricity and electric fields. IF YOU STORE A CAPACITOR, STORE IT WITH A WIRE ACROSS THE TERMINALS. (MAKE SURE YOU DISCHARGE THE CAPACITOR BEFORE PUTTING THE WIRE ON!!!) Capacitors can "regain" charge from dielectric "memory". The dielectric in a capacitor is put under electrical stress during use. During operation, this stress may cause the molecules in the dielectric to orient themselves in such a manner that they store this charge in their structure. The charge remains after the capacitor has been discharged. Later the molecules return to their original states and the charge that they "captured" ends up on the plates of the capacitor. This charge is then available to shock you. "
Trust me. I've been holding an allen wrench when it slipped lose and touched both terminals. It scared the **** out of me but it didn't hurt. Just made a nice big spark and scorched the terminals on the cap.

8.  Quote, originally posted by midwestbass » Trust me. I've been holding an allen wrench when it slipped lose and touched both terminals. It scared the **** out of me but it didn't hurt. Just made a nice big spark and scorched the terminals on the cap.

No offense, but if this is life or death, I am NOT going to simply trust you, just to be safe. Maybe your cap wasn't charged all the way or something.... it didn't hurt you probably because you weren't as good of a ground as the other terminal. [IMG]http://*****************.com/smile/emthup.gif[/IMG]

9.  Quote, originally posted by afinley » yes the hell it will if you dont discharge it properly. from a tesla coil site "Capacitors can also build up a residual charge from electrostatic sources. Capacitors have been known to accumulate a charge from various sources such as static electricity and electric fields. IF YOU STORE A CAPACITOR, STORE IT WITH A WIRE ACROSS THE TERMINALS. (MAKE SURE YOU DISCHARGE THE CAPACITOR BEFORE PUTTING THE WIRE ON!!!) Capacitors can "regain" charge from dielectric "memory". The dielectric in a capacitor is put under electrical stress during use. During operation, this stress may cause the molecules in the dielectric to orient themselves in such a manner that they store this charge in their structure. The charge remains after the capacitor has been discharged. Later the molecules return to their original states and the charge that they "captured" ends up on the plates of the capacitor. This charge is then available to shock you. "

Unless your hands are wet 14V won't shock you. It kind of like when people freak out about amperage. Yes 1mA could kill you, if the circumstances are right.
I like to watch people freak out when I grab Cap and battery terminals. You wouldn't see me do it on a cap with a Working voltage higher than 50V though.
Heck I have even grabbed a current shunt when there was a 2500A load on it, no problems.
Disclaimer: This doen't mean go out and grab terminals and what not on electronics. The fact is I know what I am doing when I have done the above stated acts, and do not suggest that anyone try it.

Modified by Non_Affiliated at 10:28 PM 1-24-2007

10.  Quote, originally posted by Non_Affiliated » Unless your hands are wet 14V won't shock you. It kind of like when people freak out about amperage. Yes 1mA could kill you, if the circumstances are right. I like to watch people freak out when I grab Cap and battery terminals. You wouldn't see me do it on a cap with a Working voltage higher than 50V though. Heck I have even grabbed a current shunt when there was a 2500A load on it, no problems.

Right! Also, no licking your caps. THEN a cap will hurt.

11.  Quote, originally posted by midwestbass » Right! Also, no licking your caps. THEN a cap will hurt.

Is that Right sarcasim I detect?
Your right though lick a cap and that person will definitly regret it.

12.  Quote, originally posted by Non_Affiliated » Is that Right sarcasim I detect?

Naw, I was just agreeing with you. The licking the cap part may have been slightly sarcastic I guess.