battery properties (#903)

* Battery params

* move category

* cleanup

* use property

* fix level

* fix battery computation

* fix level comp

* docs

docs/reference/brick/battery-property.md

@@ -0,0 +1,47 @@
+# battery Property
+
+Return the information about the battery
+
+```sig
+brick.batteryInfo(BatteryProperty.Level)
+```
+
+## Parameters
+
+* property: the kind of information
+
+## Returns
+
+* a [number](/types/number) which represents the value of the property requested.
+
+## Example
+
+Show the battery level percentage on the screen. Also, show a green light if the battery level is above 15%. If the battery level is below 15% but above 5%, show a orange light. But, if the battery level is below 5%, show a pulsing red light.
+
+```blocks
+let battery = 0;
+forever(function() {
+    brick.showString("Battery level:", 1)
+    brick.showNumber(battery, 2)
+    battery = brick.batteryInfo(BatteryProperty.Level);
+    if (battery > 15)
+    {
+        brick.setStatusLight(StatusLight.Green);
+    } else if (battery > 5) {
+        brick.setStatusLight(StatusLight.Orange);
+    } else {
+        brick.setStatusLight(StatusLight.RedPulse)
+    }
+    pause(30000)
+})
+```
+
+Or see all the values
+
+```blocks
+forever(function () {
+    brick.showValue("bat V", brick.batteryInfo(BatteryProperty.Voltage), 1)
+    brick.showValue("bat %", brick.batteryInfo(BatteryProperty.Level), 2)
+    brick.showValue("bat I", brick.batteryInfo(BatteryProperty.Current), 3)
+})
+```