Electrical Nightmare on Elm street

So..... I got a new battery.... It was smaller. Close to $300 and threw some new struts on at about 125,000 miles here. Battery shifted and shorted things. Battery charged back up just fine...(Had to tow it home)...after attempting to drive it home and was unable due to loss of power still now knowing that the battery shifted. Battery now holds 12.7 but as soon as I hook up the cables there is a drag and it drops to about 2 volts....so, loosing 10.7 roughly. Car beeps with key in the ignition door open although it acts like it has a fuseable link blown as there isn't enough power to register lights in the dash much less roll up my windows....all other electrical appears dead. When I try to start it the 2 main 1/2 relays click for a while....number one more than number two, but no signs of starting....... So like.....inverter or possibly something else. How to test? It is a Gen 1/2002 Prius. I saw inverters on Ebay for 2-4 hundred....Don't want to just throw parts... Any suggestions?