# high voltage capacitor charger - how to

Discussion in 'Electronic Basics' started by nescafe, Aug 14, 2012.

1. ### nescafeGuest

Hi.

I want to charge my capacitor bank with 72V-20A DC source.

The idea is to store 1KW in this capacitor bank and then to use this
power to run some 450V electronics.

DC source is constant so capacitors can be "recharged" all the time.
The capacitor bank should be made of 450V / 400uF capacitors and normal
power consumption of our electronics is around 800 - 900W.

Does anyone has some DIY project on this or maybe some guide how to start ?

Regards !

2. ### nescafeGuest

btw 100000uf of stronger can also be used.

3. ### Uwe HercksenGuest

Hello,

it is not possible to store 1 kW in a capacitor bank, even if it is a
very large one. But if you want to store 1 kWh this may be done, if
there are enough capacitors of a suitable capacity and voltage. The bank
might be much too large, heavy and expensive.

Bye

4. ### nescafeGuest

-------------------------
First off, do you mean that you want to draw 1 kW from the capacitors ?
-yes that's what i want

The bank might be much too large, heavy and expensive
- i agree that this could be a problem.

But i do have some additional questions.
e.g. if i dismantle some 12/220 - 2kw - DC/AC converter and if i measure
voltage on exit capacitor i will get around 250V.
Ok.
If i want to use this 250V to run some 2kw application ( working on this
voltage ) everything works OK. I tested this.

So as far as i understand this i can make the same stuff but with 450V
capacitor and with less electronic. Maybe i dont need capacitor bank ?

5. ### nescafeGuest

Can you tell us what you're trying to achieve,
-- to run one 450V circuit. This circuit is used as some kind of
controller and you can power it with 450VDC source.

To run properly the circuit needs minimum 300W.
---------------------

6. ### Jasen BettsGuest

If you can replace the rectifier on the main transformer of the 2KW
inverter with one that gives twice the voltage you'd be close to a
solution, you'd then need to mess with the feedback to reduce the
output voltage to 450V.

sounds dangerous and potentially expensive/exciting, especially if you don't
have a schematic and understanding of how the inverter is supposed to
work.

it might be better to put autotransformr on the inverter output to
step it up and rectify the result.

This is for what? A battery powered "toob" amp?

7. ### nescafeGuest

Are you trying to use a car battery inverter to step the voltage up to
450V?
- yes. I'v done this before and it worked.
There are of course few problems regarding this approach.
Safety would be on the first place, but if the you do this with some
basic/extra precaution then everything works ok.
And it's quite exciting
---------------------
Like Phil suggested if i go with capacitor bank i will not get what i
need and beside this i would spend bunch on money for nothing.
-------------------
What im doing
---------------------
I'v made electric car with reg. breaking.
Its using 3phase 11kw motor and the only thing that i need is stronger
DC/DC converter.
I dont have time to explain how all this works but to control the motor
i need 420 - 500V DC input.
DC /DC converter is connected to this motor control. Btw. 3 phase
approach is waaaay better then DC motor but as you can see there are
some problems. I can rewind motor or use some other controller or do
something else, but then again, that would not be me . To run the car
smoothly in first gear i need around 2,5kw ( first gear with fast start
and small hill ) afterwards normal consumption is much lower.
---------------------
Back to the problem ( and guys, please stay on this topic, we can talk
---------------------
I firstly connected 2x 2KW AC/DC 12/220V converters ( galvanic separated
) and it worked OK
Then i was thinking, damn, there must be a way just to change the output
capacitor and rectifier ( like Jasen suggested ) to make this work. So
my next plan is to buy some 72V DC/AC inverter and to do just that.
Change the capacitor and rectifier part.

8. ### Fred AbseGuest

How do you propose getting 450V from 72? Some sort of series-parallel
switching?
That would appear to preclude switching , as described above. Define "all
the time".