When reconnecting bateery (Ford E-150) sparks come out on negative battery terminal. Is this a shorted circuit or someting else. Also battery power drains if letf connected.t

This is normal if the cable is in contact with the post but not fully seated. And arc of electricity can jump from the post to the cable end.

A little spark at initial connection might be normal, but a lot of sparking is not. Make sure the battery post itself feels solid and not wobbly or loose, it may have broken free inside the battery. Use a dielectric grease over the battery post and terminal end, you can get that at any auto parts place. Those felt pads are also good, they slip on over the post. Then make sure the terminal is nice and tight and that the battery is bolted down. If the battery is not holding a charge, get a checkup of the charging system (battery and alternator), which can be done for free at any auto parts place. If the battery is being drained it might require a more extensive test of the alternator, or you have a parasitic draw, or possibly an electrical short somewhere that will require troubleshooting.

Both above answers make a lot of sense. I will check system tomorrow. Thanks folks!