If they did finally charge over night I dont see where the charger would be the issue..... Maybe do like rees said and run em down again and try it.... The parts house guys can be a pain to deal with sometimes. There battery testers are junk sometimes.... Tell them you want the printout showing it was good..... I had a solenoid go bad on a starter i bought from a parts house a couple years ago and the guy testing it was bypassing the solenoid and telling me it was good and I tried to explain to him he was bypassing the solenoid.... It took them calling in a manager to get the thing replaced.