Electronics > Power/Renewable Energy/EV's

Rapid charging of a 400V 11000uF capacitor.

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TheForgottenKing:
Hello everyone,

I'm in need of some sort of charge circuit that takes a low-voltage high-current input (think something like a 6S 100C lithium battery, the kind that outputs ~25V at hundreds of amps) and uses this power input to charge a 400V 11000uF capacitor extremely quickly (i.e. under half a second). For safety I'd like to charge it to ~380 V or 800 J of energy.

If my math is correct, a 4A constant-current charge that cuts off at 400 V will be enough to charge one of these in approximately half a second (1600 W into 800 J in half a second). I highly doubt there's an off-the-shelf component that can even remotely do this.

For testing, I bought this DC-DC boost converter, but it never rises above 3A of current even though it should be able to do 20. Not sure why, either I'm doing something wrong or the listing is wrong.

By the looks of it, I'm basically going to be building a DC-DC power supply, but I've never done anything like this. Is this even possible without spending thousands of dollars?

For what it's worth, I'm not opposed to doing anything shady. Ideas include putting a bunch of low-voltage constant current sources in series, or using constant-current AC LED drivers with a rectifier.

HackedFridgeMagnet:
Maybe a bridge rectifier coming off mains.

Use a variac if you want an adjustable final voltage.

TheForgottenKing:

--- Quote from: HackedFridgeMagnet on May 26, 2024, 11:47:03 pm ---Maybe a bridge rectifier coming off mains.

Use a variac if you want an adjustable final voltage.


--- End quote ---

This is meant to be portable off a DC source, but fear not, I've come up with a terrifying solution, namely reverse engineering one of the linked boost converters, simplifying the design, and then either correctly recreating one to put out 400V or just putting four of them in series.

ArdWar:

--- Quote from: TheForgottenKing on May 26, 2024, 05:15:51 pm ---...it never rises above 3A of current even though it should be able to do 20. Not sure why...

--- End quote ---

With boost converter the rating and the limiting factor is usually for input current. Make sense that a "30A" device doing 25V->100V to output 3A, allowing for 50% derating for what's look like something more like aliexpress specialty crap. Just go get bigger one.

NiHaoMike:
Take the DC/DC stage from an inverter or UPS and mod it to work in current limit mode. Would take quite a bit of electronics knowledge.

What's the application? I'm thinking a really powerful photography flash or pulsed laser, except such a large flash tube would need quite a bit more than 400V.

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