Setting a hard minimum axis value in Google Charts API

you need to set viewWindow like this:

var data = new google.visualization.DataTable();
data.addColumn('string', 'Date');
data.addColumn('number', 'Uptime');
data.addColumn('number', 'Downtime');
data.addRows([
 ['Dec 1, 1830',   99.875, 0.125],
  ['Dec 8, 1830',   99.675, 0.325],
  ['Dec 15, 1830',  99.975, 0.025],
  ['Dec 22, 1830',  100.0,  0.0]

]);

var chart = new google.visualization.ColumnChart(document.getElementById('chart_div'));
chart.draw(data,
           {width: 400, 
            height: 240, 
            isStacked: true,
            vAxis: { 
              title: "Percentage Uptime", 
              viewWindowMode:'explicit',
              viewWindow:{
                max:100,
                min:99.8
              }
            }
            }                 
          );

//edited for newer version of api