Reddit mentions of PowerMAX PMBC-55M Battery Charger, 1 Pack

http://m.autoserviceprofessional.com/article/92019/Real-world-reflashing-Cutting-through-the-smoke-and-mirrors

Not for a computer. I guess you could technically you could hack up a computer power supply but they won't output enough current and the wire insulation would make a nice fire. You need a power supply that can provide a stable well-rectified voltage and provide enough current to keep the modules alive. Since you're asking the question- you'll need one of these:

https://www.amazon.com/dp/B006GFQMHI/ref=cm_sw_r_cp_api_i_hf.dBbAEW40A1

That is the cheapest charger I could find. I've only used it a few times so I can't speak to the durability or reliability of it. You can make one but you'll need something that has excellent rectification, extremely fast voltage regulation, and will supply 50-70 amps depending on your model. For the cost, it's not worth your time unless you have tons of it.

You'll also need a j2534 programmer. You can get something from vxdiag. They're a pain to work with but gets the job done for a tenth of the price. Your other options are tried and true pass through programmers for $1000-2000 or clones off alibaba.

You'll also need a subscription. I can't remember if you have an FCA or GM car but a one day subscription is $25 and $40 respectively.

You'll also have to find software if mopar or FCA doesn't provide it, which is never easy and usually expensive.

You also have the option of hand held diagnostic tablets like certain verus models but they're generally all $1000+ (used) and some you have to buy expansions to program certain vehicles.