Victron Energy QUA125021100 Quattro 12/5000/220 Inverter Charger 120 Volt AC, 12 Volt DC

This is a very powerful inverter charger and using such a monster in a 12 volt system presents some challenges.  If you consult the instruction manual you will see that the recommended fuse is 800 Amps.   This is more than the Quattro is expected to use.  At its rated output of 5000 Watts and at 12 volts the actual current would be approx 420 amps, the reason they specify an 800 Amp fuse is to avoid nuisance tripping during big surges, like for instance when trying to start a large motor.  

If you go with an 800 amp fuse then you have to design all the rest of the circuit to meet that rating and that is where the challenge comes in.  Our biggest busbar is the Blue Sea 1990 which is rated for 1000 Amps but the next biggest is the BEP Pro Installer 5 Stud Bus Bar which is only rated for 650 Amps.  Our biggest battery switch is the Blue Sea 3000 which is rated for 600 Amps continuous and 900 Amps for 5 minutes.  We dont have any wire available that can carry 800 Amps.  The biggest wire we have at PKYS is 4/0 which can carry 440 amps.  There is provision to double up cables to the MultiPlus so you could put dual 4/0 cables and use two 4/0 fuses and use a double pole battery switch if you can find one with a high enough rating.  Anyway I am just pointing out the challenges involved in installing a Quattro this powerful in a 12 volt system.