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Recharging the LIPO Batteries :

ROFI has two LIPO (Lithium Polymer) batteries, one in each foot.  Each battery has two 3.7v cells that are in series to an output of 7.4v. The two batteries are connected to ROFI in parallel so the output voltage of the two connected batteries going into the robot is 7.4v.  It should be noted that when fully charged the batteries will output 8.4 volts and then they are ready to be recharged they will drain down to 6.4v.  Never drain the batteries below 6.4 volts or they can be permanently damaged! ROFI has no warning system for low batteries, so it is important to check the voltage using a volt meter every time before you run the robot. To recharge the batteries follow these steps:
  1. Unplug the power connector from the batteries to the robot.
  2. Unplug each battery power connector from the power extension cord that runs up ROFIs legs.
  3. Plug the left battery power connector into the LIPO balance charger.
  4. Plug the left battery voltage monitor cable into the smallest (3 prong) connector on the LIPO balance charger's monitor connector board.
  5. Follow the instructions from your LIPO balance charger's manufacturer to recharge the battery to full capacity (8.4v).  Here are the instructions for the charger that we used. Be careful ... improper charging can damage your battery and cause fires!
  6. Unplug the left battery from the LIPO balance charger (both power and monitor).
  7. Unplug your LIPO balance charger from the wall.
  8. Repeat steps 3 through 7 for the right battery.
  9. Plug each battery power connector into the battery extension wires that run up each leg.
  10. Be sure to charge both batteries fully so that they have the same voltage level. Failure to do this can result in damage to one or both batteries.

Recharging the Android Tablet :

ROFI's Android tablet has its own battery that will last for several hours on its own.  During normal operation you won't need to externally recharge the Android tablet because the USB host shield will continually recharge the  the tablet when they are connected (and the robot is powered on).  When you first build ROFI, or If the robot is left idle for a long time the battery on the Android tablet will run down to 0.  When this happen it can take up to 10 minutes of powering the tablet before the battery charges enough for it to turn its screen on.  You can avoid this by charging your Android tablet by connecting it to your computer as shown in the diagram.