If there is a charge controller in the suitcase you should be good. You might want to put a 15 or 20 amp fuse in line just to protect the wiring. Use beefy wire (8 or even 6) to reduce voltage drop from the panel. If you have a negative bus bar, you could connect the negative from the panel to that.
You might also connect a voltmeter to the battery to make sure the panel is not overcharging. Something permanent connected directly to the battery would be ideal. Even better would be a battery monitor like the Bogart Trimetric. It will tell you the state of charge of the battery, voltage, and amps IN/OUT.
