[KenWittlief]

from an engineering perspective, you can buy 6 amp battery chargers off the shelf that have been extensively tested, that have built in safety features, and are UL approved - and they will charge the batteries as fast as is possible without damaging them

if you build your own custom charger, you cannot charge the batteries any faster, you will take away limited time from other (robot) work you could be doing instead and you will have a much greater risk of system failure - either not charging the batteries or cooking them to some degree

So as an engineer I would say, why custom design a functional system that you can buy commercially off the shelf as a commidity item, when all you have to gain is risk?

I would recommend spending your valuable time on some other design project that will make your team more competitive, or helpfull to other teams at the event - something that you cant buy at Wallmart because you havent invented it yet :c)