So... As stated before... If considering doing the DIY power supply for batteries to replace the supplied one, You cannot just put 1200watts from a single terminal to a single battery, you would have to either put enough batteries at once to distribute the load and bring it down to 240watts or less per each charging terminal, or regulate the amperage going into each terminal to the 240watts or less for each battery. Once within this range, the batteries can, and will charge....If you are in the market for Power supplies just understand this limitation...
Please read these threads as they have the collective information presented:
lvl.3