1. Available at: www.etcurr.comLesson 1.1 – maintain VEX rechargeable power pack Maintain VEX Rechargeable Power Packs

2. Available at: www.etcurr.comLesson 1.1 – maintain VEX rechargeable power pack Maintain VEX Rechargeable Power Packs  Performance Objective: Given a VEX robotics system, maintain VEX rechargeable power packs so the system functions as required.  Enabling Objectives:  define the following terms: ohms, volts, milliamps, amp hours, electricity, alternating current, direct current  identify 7.2V and 9.6V power packs  test power pack voltage using a multimeter  explain how to charge the 7.2V power pack versus the 9.6V power pack  set-up the battery charger  identify the charging sequence when charging two power packs  describe the relationship between the status lights on the charger and the condition of the power pack(s) being charged

3. Available at: www.etcurr.comLesson 1.1 – maintain VEX rechargeable power pack Battery Packs  7.2 volt robot battery  Capacity: 1000-2000 mAh  Charging time: 1.4 – 2.8 hrs  9.6 volt transmitter battery  Capacity: 700 – 1000 mAh  Charging time: 1.4 – 2.0 hrs NOTE: the batteries used to power VEX systems are also known as power packs

4. Available at: www.etcurr.comLesson 1.1 – maintain VEX rechargeable power pack Electricity  Electricity is the movement of electrons; particles with a negative charge.  Electrical systems utilize either alternating current (AC) or direct current (DC).  VEX robotic systems utilize batteries that supply DC.

5. Available at: www.etcurr.comLesson 1.1 – maintain VEX rechargeable power pack Electrical units of measurement  There are three units of measure that are important when looking at an electrical circuit:  Amps  Volts  Ohms

6. Available at: www.etcurr.comLesson 1.1 – maintain VEX rechargeable power pack Amps (A)  Amps is the measure of electrical current.  Current is the amount of electrons flowing through a conductor in a given period of time.  Amps can be measured using a multimeter.

7. Available at: www.etcurr.comLesson 1.1 – maintain VEX rechargeable power pack Volts (V)  Volts is the measure of force or pressure moving electrons.  Volts can also be measured using a multimeter.

8. Available at: www.etcurr.comLesson 1.1 – maintain VEX rechargeable power pack Ohms (Ω)  Ohms is the measure of resistance to the flow of electrons.  Multimeter can be used to measure ohms.

9. Available at: www.etcurr.comLesson 1.1 – maintain VEX rechargeable power pack Digital Multimeter  A multimeter can be used to measure both AC and DC voltage, amperage, ohms, and continuity.

10. Available at: www.etcurr.comLesson 1.1 – maintain VEX rechargeable power pack Digital Multimeter Ohms DC Amps AC Amps AC Volts DC Volts DC millivolts Continuity

11. Available at: www.etcurr.comLesson 1.1 – maintain VEX rechargeable power pack Measuring DC Voltage  Step 1: Set multimeter on DC voltage  Step 2: Plug red probe in volts, ohms, and continuity socket  Step 3: Be sure black probe is in the com socket

12. Available at: www.etcurr.comLesson 1.1 – maintain VEX rechargeable power pack Measuring DC Voltage  Step 4: Place probes in socket of battery pack, red to red (+), black to black (-)  Step 5: Note voltage value from the multimeter  If reading is negative, you can either ignore the minus sign or reverse the probes

13. Available at: www.etcurr.comLesson 1.1 – maintain VEX rechargeable power pack Normal battery readings  A freshly charged 7.2 V (nominal value) battery will read approximately 8.2 volts  A freshly charged 9.6 V(nominal value) battery will read approximately 10.4 volts  When a battery reaches its nominal value, it will need to be recharged

14. Available at: www.etcurr.comLesson 1.1 – maintain VEX rechargeable power pack CAUTION using multimeter  DO NOT test the batteries using any other set-up on the multimeter or you may risk damaging the multimeter.

15. Available at: www.etcurr.comLesson 1.1 – maintain VEX rechargeable power pack Milliamp-hours (mAh)  An amp-hour is the amount of amps a battery can deliver for one hour  The prefix milli is used to indicate one thousandth (1/1000) of a unit in the SI measurement system  For example: a millimeter (mm) is one thousandth (1/1000 or 0.001) of a meter; a milliamp-hour (mAh) is 0.001 of an amp-hour.

16. Available at: www.etcurr.comLesson 1.1 – maintain VEX rechargeable power pack Milliamp-Hours (mAh)  2000 mAh  The battery can produce a steady charge of 2 amps for one hour  1000 mAh  The battery can produce a steady charge of 1 amp for one hour

17. Available at: www.etcurr.comLesson 1.1 – maintain VEX rechargeable power pack Battery Charger  Battery charger and battery packs  Transformer and chord

18. Available at: www.etcurr.comLesson 1.1 – maintain VEX rechargeable power pack Setting up the battery charger  Plug transformer ‘s 120VAC cord into wall outlet  Plug transformer’s 16VDC cord into the battery charger

19. Available at: www.etcurr.comLesson 1.1 – maintain VEX rechargeable power pack Battery charger default setting  Battery packs properly installed in charger  Default override switches: These switches will be engaged when the 7.2 Volt battery is properly installed

20. Available at: www.etcurr.comLesson 1.1 – maintain VEX rechargeable power pack Properly inserting batteries  When charging 7.2 volt batteries it is very important the default override switches are pressed down. If these switches are not pressed down, the 7.2 battery pack will be charged to the higher default setting, ruining it. Switch is pressed

21. Available at: www.etcurr.comLesson 1.1 – maintain VEX rechargeable power pack Charging order of batteries  Whichever battery is plugged in first is the first one to charge.  The second battery will be charged when the first is completely charged.

22. Available at: www.etcurr.comLesson 1.1 – maintain VEX rechargeable power pack LED Status lights  Whichever LED is on indicates which battery is charging  If the LED is flashing it indicates there is a problem  If the LED is off it means the battery is fully charged or waiting for the other battery to charge

23. Available at: www.etcurr.comLesson 1.1 – maintain VEX rechargeable power pack Flashing LED  If LED flashes, try a different battery pack  If the LED still flashes, try another charger

24. Available at: www.etcurr.comLesson 1.1 – maintain VEX rechargeable power pack The End Have fun and be safe