For safety, I recommend this type of battery connector that completely covers the terminal and quickly clips on & off. For example:
(you may find them cheaper elsewhere)
I solder in a brass tube 4mm inner diameter so that I can simply use 4mm test plugs to connect up anything.
I advise including a 10 amp fuse in one lead (or slightly greater than your maximum current will be).
You may like to include a voltmeter to monitor your battery, for example:
or even one that shows both voltage & current: