battery.py

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import roslib;roslib.load_manifest('create_dashboard')
import rospy

from rqt_robot_dashboard.widgets import BatteryDashWidget

def non_zero(value): 
   if value < 0.00001 and value > -0.00001: 
      return 0.00001 
   return value

class TurtlebotBattery(BatteryDashWidget):
    def __init__(self, name='battery'):
        super(TurtlebotBattery, self).__init__(name)

        self._power_consumption = 0.0
        self._pct = 0.0
        self._cap = 2.7
        self._char_cap =2.7
        self._time_remaining = 0.0

    def set_power_state(self, msg):
        last_pct = self._pct
        last_plugged_in = self._charging
        last_time_remaining = self._time_remaining
        self._char_cap = 0.8*self._char_cap +0.2*float(msg['Charge (Ah)'])
        #make sure that battery percentage is not greater than 100%
        if self._char_cap < float(msg['Capacity (Ah)']):
          self._cap = float(msg['Capacity (Ah)'])
        else:
          self._cap = self._char_cap
    
        self._power_consumption = float(msg['Current (A)'])*float(msg['Voltage (V)'])
        #determine if we're charging or discharging
        if float(msg['Current (A)'])<0:
          tmp = (float(msg['Charge (Ah)'])/non_zero(float(msg['Current (A)'])))*60.0
        else:
          tmp = ((float(msg['Charge (Ah)'])-self._cap)/non_zero(float(msg['Current (A)'])))*60.0
    
        self._time_remaining = 0.8*self._time_remaining + 0.2*tmp
    
        self._pct = float(msg['Charge (Ah)'])/self._cap
    
        if self._pct == 1 and float(msg['Current (A)']) == 0:
            self._charging = True
        else:
            self._charging = (float(msg['Current (A)'])>0)
            
        self.update_perc(self._pct*100)
        self.update_time(self._pct*100)