Is it ok to overcharge a capacitor?

#1 · 1 Jun 2010

I have 55F 2.5V from Ben. It took 12 minutes 17 seconds to reach 3V, 0.5V more than rated voltage. I actually take it to 3.4V. Anyone here have experience with capacitor? What overcharging do to a capacitor?

This photo show less voltage, maybe because I accidently short it since I notice it instantly get warm. much warmer than right after charging.

COP measurement: Input is 600mA at 12V, 7.2 joules each seconds, 5306.4 joules total. Energy stored on the capacitor = 0.5 x C x V^2 = 0.5 x 55000000 x 3 x 3 = lol forget it. I think either my calculation screw up or my circuit screw up the cap....

EgmQC

#2 · 1 Jun 2010

sucahyo wrote:
I have 55F 2.5V from Ben. It took 12 minutes 17 seconds to reach 3V, 0.5V more than rated voltage. I actually take it to 3.4V. Anyone here have experience with capacitor? What overcharging do to a capacitor?

This photo show less voltage, maybe because I accidently short it since I notice it instantly get warm. much warmer than right after charging.

COP measurement: Input is 600mA at 12V, 7.2 joules each seconds, 5306.4 joules total. Energy stored on the capacitor = 0.5 x C x V^2 = 0.5 x 55000000 x 3 x 3 = lol forget it. I think either my calculation screw up or my circuit screw up the cap....

In the formula , C is in farad so ((3.4v * 3.4v) * 55) * 0.5 = 317.9 Joules

sebosfato

#3 · 1 Jun 2010

hi suchayo

If it's electrolitic it can explode or damage the dielectric, this will cause the capacitance to become smaller if it don't stop working.

Regards

EgmQC

#4 · 1 Jun 2010

And btw , measure the capacitance, i never seen in my entire life a capacitor with the exact capacitance as wrote on it, usually for low quality capacitor its 10% margin error and for high quality 1% or less, 5-10% on a 55 farad its a massive difference and can lead to wrong calculation if not tester before.

Matthew Jones

#5 · 1 Jun 2010

I have taken 100 volt caps up to 300 volt. They were good caps and still are. They test out exactly as they should. They have not changed in there Farrad rating even though they hold more voltage.
Of course I did this with pure voltage (radiant). I suspect bad things happen if amperage is used along with high voltage.

Play it by ear and don't hold on to them while your charging. They can blow and it can be violent.

Cheers

Ted Ewert

#6 · 1 Jun 2010

The rating on a cap is the "working" voltage, not the maximum voltage.

sucahyo

#7 · 1 Jun 2010

EgmQC wrote:
In the formula , C is in farad so ((3.4v * 3.4v) * 55) * 0.5 = 317.9 Joules

Thanks for the correction

.

sebosfato wrote:
If it's electrolitic it can explode or damage the dielectric, this will cause the capacitance to become smaller if it don't stop working.

Matthew Jones wrote:
Play it by ear and don't hold on to them while your charging. They can blow and it can be violent.

Thanks. I forgot that electrolytic will allow electrolysis and release oxygen/hydrogen bubble and may dent the cap or puffing. I should always monitor it. Thanks for the warning both of you

.

EgmQC wrote:
And btw , measure the capacitance, i never seen in my entire life a capacitor with the exact capacitance as wrote on it, usually for low quality capacitor its 10% margin error and for high quality 1% or less, 5-10% on a 55 farad its a massive difference and can lead to wrong calculation if not tester before.

Matthew Jones wrote:
I have taken 100 volt caps up to 300 volt. They were good caps and still are. They test out exactly as they should. They have not changed in there Farrad rating even though they hold more voltage.

Ted Ewert wrote:
The rating on a cap is the "working" voltage, not the maximum voltage.

Thanks, that explain it

.

Web000x

#8 · 1 Jun 2010

Careful

YouTube - Exploding Capacitor

If you overcharge it, you might want to add a shield just to be safe.

Dave

sucahyo

#9 · 1 Jun 2010

Web000x wrote:
YouTube - Exploding Capacitor

If you overcharge it, you might want to add a shield just to be safe.

Dave

Scary

, thanks for the video

.

sucahyo

#10 · 10 Jun 2010

I forgot to time my charging and overcharge my 55F capacitor again today. Seeing that it become hto I immediately sunk it on a water botol in front of me. It produce rigorous bubble for minutes .... I guess the bubble is H2 or O2, which may explode if there are spark around.