You can pickup these old computer power supplies from recycling centre for next to nothing - or even hit up your local computer store. us this to power your DC chargers
Specifications:
Product name: ATX power supply board
Model: XH-M229
Compatible with the port: ATX (compatible with partial BTX type)
The PIN number: 24pin
Switch: Yes
Number of sets of output: Four sets of different voltage
Size: 12.8x4.8cm/5.04x1.89"
Package Includes:
1 x Power Supply Test Module