Accordions collapse by default in mobile and expanded by default in desktop Bootstrap 3 responsive

Try this:

$(document).ready(function(){
  var windowWidth = $(window).width();
  if(windowWidth <= 1024) //for iPad & smaller devices
     $('.panel-collapse').removeClass('in')
});

In your css:

@media (max-width: 768px) 
{
  .collapse.in {
        display: none;
    }
}