Hooking up battery to newly rewired car

It can be lots of things. Check with your meter between battery cables and what is the OHM resistance?

Ohms law, google it for all the calcs. It will give you the amp current based on 12.5 or 13v as E. If you are under .5 amps I would not be concerned for start up. you can better determine E by reading voltage on your battery in current state of charge. Keep looking and unplug as needed. Not familiar with the EZ wiring setup as I prefer the factory wiring.