Making a Step-up DC transformer

[Xforce]

TL;DR Summary

Step downs are common, but seems step ups are rare?

For one of my scientific projects, I want to charge a couple of 450V capacitors in parallel, which I get the power from household electricity, because a lot of lithium polymer batteries can be expensive and take up a lot of space.
The problem is, the power supply gives a 250V AC, and and I need 450V, or at least around 400 volts of DC. A common AC-DC transformer I can get at a electronic market turns the AC power to a 12V or 24V DC, and that’s pretty useless on its own. The other way is use 4 diodes to ensure the electricity goes one-way, so I can make DC, this method does not change voltage, therefore I get 250 volts, which is still not enough...
Is there a way I can get the high DC voltage I want? I heard Tesla car batteries are at 400 volts and the car can charge from household electricity. But I have no wielding devices and no professional skills in electric engineering. Can I still do it?

 

[mfb]

Can I still do it?

Not safely at least. Tampering with power from the electricity grid is a bad idea, trying to transform their voltages to higher values is a really bad (and potentially lethal) idea.

Why do you want to charge 450 V capacitors? There might be a better, safe option.

 

[Xforce]

Not safely at least. Tampering with power from the electricity grid is a bad idea, trying to transform their voltages to higher values is a really bad (and potentially lethal) idea.

Why do you want to charge 450 V capacitors? There might be a better, safe option.

I’m hoping for the better and safer option, I don’t know how to charge them.
I’m using high voltage capacitors for a linear electromagnetic launcher (a more scientific name) , that uses Ampere force to launch stuff, as current goes through the projectile, and the force exerted depends on the current. So I need high voltage capacitors for rapid discharging so the launch will be more successful.

 

[Xforce]

By the way, I find this circuit on the internet, which outputs 390V maybe? It requires 24V DC input, which I certainly can do. But it seems a bit complicated and requires lots and accurate wielding?

 

[berkeman]

I don’t know how to charge them.
I’m using high voltage capacitors for a linear electromagnetic launcher

Well, that's two reasons to shut down this thread. You don't have experience with high voltages (and moderately high power), and you are still trying to build a rail gun. Please focus on safer projects while you build your skillset.