diff --git a/sumorobot.js b/sumorobot.js
index bc4642a..15932b5 100755
--- a/sumorobot.js
+++ b/sumorobot.js
@@ -55,7 +55,7 @@ Sumorobot.prototype.connect = function() {
         var data = evt.data.replace(/'/g, '"').toLowerCase();
         console.log(data);
         var battery = JSON.parse(data)["battery_voltage"];
-        battery = Math.round((((battery - 3.0) * 100) / (4.2 - 3.6)));
+        battery = Math.round((((battery - 3.0) * 100) / (4.2 - 3.0)));
         $("#battery").html(battery + "%");
         $("#bar").html("Battery");
         $("#bar").addClass("connected");