Ajax Reload
I found my Google Charts are missing after reloading charts via Ajax.
google.load("visualization", "1", {
packages : ['corechart']
});
And I found one solution very easy to solve the problems: Just add an option (highlighted) into your code like this:
Callback
google.load('visualization', '1', {
packages : ['corechart'], 'callback': drawChart
});
It works fine after every Ajax.