# Charging a 450v 6800uF DC capacitor

Discussion in 'General Electronics Discussion' started by babuss9595, Apr 8, 2015.

1. ### babuss9595

1
0
Apr 8, 2015
i am trying to charge a capacitor of 450v 6800uF, please help me with the safest way for charging the capacitor. if possible please provide a suitable circuit diagram with what are the things that i should use in them.

[mod edit ... this isn't a project and have removed from that section]

Last edited by a moderator: Apr 8, 2015
2. ### davennModerator

13,709
1,909
Sep 5, 2009
hi there
welcome to EP

what are you trying to achieve with charging this capacitor ?
do you have any understanding of the dangers of what you are wanting to do ?

Dave

3. ### Colin Mitchell

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Aug 31, 2014
Charge it via a 10k resistor and wait for 30 minutes.

Arouse1973 likes this.
4. ### Gryd3

4,098
875
Jun 25, 2014
Colin, you know nothing of what the op will even charge this with. There are far too few details to safely suggest anything, your going to get someone hurt. (Please redact your post)

@babuss9595 can you please answer Dave's question.
Ideally we want to know:
-what you want to charge it from
-what voltage you want to charge it too
-how you will use the charge in the capacitor
-if you understand that capacitors can put out an incredible amount of amperage which can cause harm to persons and property

5. ### hevans1944Hop - AC8NS

4,547
2,122
Jun 21, 2012
From the nature of the query it is clear that the original poster has absolutely no idea of what they are attempting to do. This size capacitor charged to its rated voltage is capable of serious injury or even death. If I were moderating this forum I would close this thread.

6. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,448
2,809
Jan 21, 2010
Let's see, 450V, 6800uF... That's about 680 joules. 10 joules of electrical energy is sufficient to kill you in the right circumstances, so you might understand why we're not sure this is a great idea.

I understand your sentiment. However if the OP ever gets back to us and we find out what he's trying to do, perhaps there may be a safe(r) way?

As it is, this thread is just a list of people, all saying the same thing (except for Colin of course). It's not harmful.

7. ### hevans1944Hop - AC8NS

4,547
2,122
Jun 21, 2012
Okay, in that case all we need is one 1N4007 rectifier connected across India's 240 VAC power line in series with the 6800 μF capacitor, anode of diode to phase side of line, cathode of diode to positive terminal on capacitor, capacitor negative terminal to neutral side of power line. It would charge up right quickly to about 340 volts, but the initial charge current would be very high. It might even exceed the one-cycle surge current rating of the diode. So, if you want to charge without blowing any fuses or popping a circuit breaker, do what @Colin Mitchell suggested and put a 10 kΩ, 20 watt, power resistor in series with the phase lead of the power line, just after the diode cathode and before the positive terminal of the capacitor. This will introduce about a 68 second time-constant and limit the initial charging current to less than 34 mA. It will take several minutes for the capacitor to charge to the peak of the line voltage after you turn on the mains power.

Safely discharging the charged capacitor is another matter. I usually use an insulated "shorting stick" holding an insulated wire taped to the stick, with that end stripped back and exposed. The other end of this wire is attached to "ground" or neutral of the power line. To discharge the capacitor first turn off the mains power. Then, holding the insulated stick, touch the bare end of the wire taped to the stick to the junction of the diode and the 10 kΩ power resistor. Leave it there for awhile, at least five minutes, until the capacitor is safely discharged. You should attach a voltmeter across the capacitor and leave it connected while doing all this so you can monitor the capacitor voltage. Do not allow the capacitor voltage to exceed 450 VDC. That is, if the mains voltage is greater than 240 VAC, disconnect the mains if the capacitor voltage approaches 450 VDC. Never touch the capacitor terminals while mains voltage is on, or until the capacitor is safely discharged with the mains voltage off.

Remember, you are dealing with potentially lethal voltages capable of very high currents when the capacitor is charged. Keep all body parts away from the circuitry at all times.

8. ### Colin Mitchell

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Aug 31, 2014
put a 10 kΩ, 20 watt, power resistor in series

The resistor needs to be 5 watt, because it is only half-wave charging and the current will drop from (35mA) 17mA to near zero, in 2 x 145secs.

9. ### hevans1944Hop - AC8NS

4,547
2,122
Jun 21, 2012
The resistor power rating was conservative because (1) I also recommended that it be used to discharge a fully charged capacitor and (2) I was too lazy to calculate how much power it would dissipate in a single discharge cycle (about two watts). So, I agree with you that a 5 watt resistor should work just fine.

5,165
1,087
Dec 18, 2013
Important! What voltage do you want to charge this capacitor to. 450 Volts appears to be the max voltage for this capacitor. What are you trying to do..............hello hello you still there?

davenn likes this.
11. ### davennModerator

13,709
1,909
Sep 5, 2009
LOL looks like he/she isn't going to return