Making an umbilical/pigtail cord

I'd do a quick continuity test to determine which of those is ground (one of the four prongs we'll assume). After that (once determined and hooked up), jump a hot wire to each of the other three; when the markers come on, you're got that nailed.

Determining which is the charging feed would be my next game; I'd probably just disconnect the battery, run a jumper to my tester, then use a hot wire against the remaining two prongs and see if the tester flinches.

I offer this as a layman's way to chase a solution.