added low battery alert

src/main/java/frc/robot/Robot.java

@@ -12,6 +12,14 @@
 import frc.robot.LimelightHelpers.PoseEstimate;
 
 public class Robot extends TimedRobot {
+
+    private static final double kLowBatteryVoltage = 11.8;
+    private static final double kLowBatteryDisabledTime = 1.5; //seconds
+
+    private final Timer batteryTimer = new Timer();
+    private boolean lowBatteryAlert = false;
+
+
     private Command m_autonomousCommand;
 
     private final RobotContainer m_container = new RobotContainer();
@@ -124,6 +132,8 @@ public void robotInit() {
             DriverStation.silenceJoystickConnectionWarning(true);
         }
 
+        batteryTimer.start();
+
     }
 
     @Override
@@ -164,6 +174,19 @@ public void robotPeriodic() {
             }
             */
         }
+
+        if(DriverStation.isEnabled()){
+            batteryTimer.reset();
+        }
+        double batteryVoltage = RobotController.getBatteryVoltage();
+
+        if(batteryVoltage<= kLowBatteryVoltage && batteryTimer.hasElapsed(kLowBatteryDisabledTime)){
+            lowBatteryAlert = true;
+        } else {
+            lowBatteryAlert = false;
+        }
+
+        SmartDashboard.putBoolean("LowBattery", lowBatteryAlert);
     }
 
     @Override
@@ -221,4 +244,4 @@ public void simulationPeriodic() {
         // If you have physics simulation, put it here
         // For now: do nothing fast
     }
-}
+}