Check out this manual. I don't think your battery is lithium; it's most likely a sealed lead acid battery (SLA, sometimes referred to as AGM, or absorbent glass mat). They tend to be a lot smaller than regular car batteries in terms of dimensions (I have some that are about 3"x4"x5") but are much heavier than lithium batteries would be.
https://onedrive.live.com/?cid=4770EE572F47C07C&id=4770EE572F47C07C%21135&parId=4770EE572F47C07C%21110&o=OneUp (page 111 by the internal numbering, or page 125 by PDF numbering)
Below is the relevant picture:
SAFETY NOTE: be sure to read the manual regarding the battery strap, as it is apparently used to hold some cables and hoses in place as well, otherwise they may get damaged by moving parts!
It doesn't show where the two smaller wires go, but as suggested by @alephzero , they likely go to the chassis or some other connectors -- definitely not the battery itself. The "L" shaped connector is your positive lead, and it looks like the bend is meant to go around the battery's cap (a sort of keying mechanism); similarly, the flanged connector is your negative lead and is designed to go around the top of the negative post.
EDIT: Since the other two connectors are standard ring terminals (no keying/etc) they probably connect onto standard screw posts with an appropriate nut to secure them. If you're lucky (or just had the foresight to put the nuts back on the posts so you didn't lose them, leaving two posts with no wires and loose nuts) the posts should be relatively self-evident. Hold the battery cables into approximate position (especially the positive lead, which is tethered to one of the other cables) and the play in that unknown cable should give you a much smaller search area in which to figure out where it should connect to.