what may cause the battery to go very low? on 2004 Chevrolet Venture

I have replaced the alternator and battery once, about a year ago i hit a iron lid on the road and put a hole in the oil pan, then this problems atarted to happened. with that all the gauges on the panel started to go crazy....

Asked by for the 2004 Chevrolet Venture
You may have a draw on the battery draining it when shut off. You may have a failing/failed alternator. Have checked at a qualified shop.