diff --git a/apps/bigdclock/bigdclock.app.js b/apps/bigdclock/bigdclock.app.js
index dba60183c..a3691539b 100644
--- a/apps/bigdclock/bigdclock.app.js
+++ b/apps/bigdclock/bigdclock.app.js
@@ -11,6 +11,8 @@ Graphics.prototype.setFontOpenSans = function(scale) {
 };
 
 var drawTimeout;
+var lastBattCheck = 0;
+var width = 0;
 
 function queueDraw(millis_now) {
     if (drawTimeout) clearTimeout(drawTimeout);
@@ -26,12 +28,16 @@ function draw() {
         m = date.getMinutes();
     var d = date.getDate(),
         w = date.getDay(); // d=1..31; w=0..6
-    const level = E.getBattery();
-    const width = level + (level/2);
     var is12Hour = (require("Storage").readJSON("setting.json", 1) || {})["12hour"];
 //    var dows = require("date_utils").dows(0,1);
     var dows = ["SU","MO","TU","WE","TH","FR","SA"];
 
+    if (date.getTime() >= lastBattCheck + 15*60000) {
+      lastBattcheck = date.getTime();
+      width = E.getBattery();
+      width += width/2;
+    }
+
     g.reset();
     g.clear();
 
@@ -63,7 +69,7 @@ function draw() {
       g.setColor(0,1,0);
       g.fillRect(73,162,162,168);
     }
-    if (level < 100) {
+    if (width < 150) {
       g.setColor(g.theme.bg);
       g.fillRect(12+width+1,162,162,168);
     }