Question on building DIY power supply.

[AndyD]

He is using a PC power supply at the moment, but it does not deliver sufficient power.
.............The psu delivers 200 watt, but the voltage drops to 11 v, causing the charger to draw more amps at 11v, generating excessive heat.

Linking 2 x PC PSU's together will end up with scrap. 400w and 600watt PC power supplies are basically entry level nowadays and easily available at low cost.

A '17/18 v 60 amp' powersupply is going to be massive. At 60A the wiring alone will need to be 10-16mm2.