It's always a good idea to charge larger batteries using a wall wart. Less strain on the 'puter's power supply.
Cheaper to replace a $5 or $10 wall wart then a PSU.
BTW. if you are good with a few tools and have a very old computer laying about with a functional PSU, here is an excellent Saturday afternoon project. ATX to Lab Bench Power Supply Conversion
Cheap and suprisingly effective way to power DC things on your workbench.
PSU's are fine for anything less than 5 volts...
but, for boys with bigger toys this is a better alternative
25A 14v DC Power Supply (350W) $39