available at: 1.1 – maintain vex rechargeable power pack maintain vex rechargeable power packs
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Available at: www.etcurr.com Lesson 1.1 – maintain VEX rechargeable power pack
Maintain VEX Rechargeable Power Packs
Available at: www.etcurr.com Lesson 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
Available at: www.etcurr.com Lesson 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
Available at: www.etcurr.com Lesson 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.
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Electrical units of measurement
There are three units of measure that are important when looking at an electrical circuit: Amps Volts Ohms
Available at: www.etcurr.com Lesson 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.
Available at: www.etcurr.com Lesson 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.
Available at: www.etcurr.com Lesson 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.
Available at: www.etcurr.com Lesson 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.
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Digital Multimeter
Ohms
DC Amps
AC Amps
AC Volts
DC Volts
DC millivolts
Continuity
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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
Available at: www.etcurr.com Lesson 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
Available at: www.etcurr.com Lesson 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
Available at: www.etcurr.com Lesson 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.
Available at: www.etcurr.com Lesson 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.
Available at: www.etcurr.com Lesson 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
Available at: www.etcurr.com Lesson 1.1 – maintain VEX rechargeable power pack
Battery Charger
Battery charger and battery packs
Transformer and chord
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Setting up the battery charger
Plug transformer ‘s 120VAC cord into wall outlet
Plug transformer’s 16VDC cord into the battery charger
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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
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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
Available at: www.etcurr.com Lesson 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.
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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
Available at: www.etcurr.com Lesson 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