Does anyone know methods for drawing large amounts of current, like hundreds of Amps, for testing purposes?
Like testing how much current can batteries give out before they explode/melt, or how much current can a pair of cables take before they melt etc?
I know there are some devices that do this but they are very expensive. I was hoping it can be done in other ways
Depends on how much control you want of the current, a car starter relay can handle fairly high current and it cheap, but you will need an resistor to limit the current.
You could also use an electronic relay like a couple of good high current mosfet transistors in parallel.
For controlled current you can buy electronic loads, but they cost money when you want that about of current.
Carbon Pile load tester may be of use for some DIY setup?
https://www.harborfreight.com/500-amp-carbon-pile-load-tester-91129.html