Lithium Polymer Charging Through Conduction Breaking down the Procedure

A.R. Drone 2.0 1000mAh Battery Back Label on our Battery Storage Capacity = 1000mAh Total Nominal Voltage = 11.1V Nominal Voltage = 11.1/3 = 3.7v/cell Fully charged = 4.2v/cell Minimum safe charge = 3.0v/cell C (Discharge Rate) = The fraction of an hour it takes to discharge. 1 C discharges the battery in 1/1 hours. 10C discharges the battery in 1/10 hours. 1000mA in 6 minutes. S stands for Series. Along with ‘3’ represents 3 cells in series. 3 cells in series is then written 3S. P stands for Parallel. No Cells are in parallel in this case.

Battery Damage Temperature Overcharging: Rapid Charging Undercharging - Capable of operating right up to 60ºC or 140ºF, and conversely, don’t work very well in cold temperatures. - If the battery gets hot, battery life is decreased. Overcharging: Cells over 4.2V or 12.6V (3x4.2V/cell) are ‘overcharged’. -Overcharging can significantly decrease lifespan of the battery and potential explosion. Rapid Charging - Can cause swelling similar to overcharging 1C Charging Rate standard. Causes rapid temperature increase. Undercharging - Reducing the cells under 3V decreases battery lifespan. - Reducing to 2.5V causes permanent and sometimes fatal damage. Damaged Lithium Polymer Battery – Swelling caused by overcharging. https://en.wikipedia.org/wiki/Lithium_polymer_battery#/media/File:Expanded_lithium-ion_polymer_battery_from_an_Apple_iPhone_3GS.jpg

Lithium Polymer Charging Restraints Single Cell Charge Cell voltage is quickly brought to its nominal value (3.7V). Cell is rapidly charged (1C Rate) for approximately an hour. Charge current then decays as capacity increases logarithmically towards 100%. This decay is to avoid overcharging and to also avoid overheating. Source: http://electronicdesign.com/site-files/electronicdesign.com/files/archive/electronicdesign.com/files/29/12195/figure_01.gif

How Quickly Can the Battery be Charged? It is possible to safely charge from ~15-20% To ~80% If temperatures remain under 65 Celsius. Theoretically: 1C at 1000mA/h would take ~1 Hour It is unsafe to charge from 0% to 100% at a constant current An excessive flow can dislodge particles of active material from the positive plates, resulting in reduced battery life.

Cell Charging https://commons.wikimedia.org/wiki/File:AR_Drone_Battery.jpg

7805 3-Terminal Adjustable Regulator Why do we need a regulator? The output of AC/DC conversion will be variable, adds stability. Bring voltage to appropriate operating range. Capable of supplying up to 1.5 A over an output-voltage range of 1.25 V to 37 V. It requires only two external resistors to set the output voltage.

Typical AC to DC Rectifier Mains-frequency regulated transformer supply Example of an AC to DC conversion circuit (a generic schematic) http://electronics.stackexchange.com/questions/41938/230v-ac-to-5v-dc-converter-lossless

Initial Pspice Simulation Testing

Initial Pspice Results using Flooded Cells This design only incorporates a constant charging current but will insure that all cells are being charged at the same rate. Further design adjustments will incorporate a stepdown and cutoff switch for end charging.

Problems with this Design Charging current sensitive to temperature variation Charging cutoff not yet incorporated Does not include a reduced charging phase (I, III) Solution: A controller can be implemented to control these issues

This picture was taken from a product catalog and is only being used in this presentation to demonstrate current market available controllers, specifically for battery charging. Many options are available and are currently being looked into. We are primarily looking for a controller that can adjust for temperature and supplied the need step downs/cutoff.

Future Considerations Increasing battery storage increases weight but the increased storage can increase operating times 8-10 minutes flying (1000mAh) 12-18 minutes flying time (1500mAh) 20-30 minutes of flying time (2000mAh) These estimates are supplied by Parrot under product specifications. Realistically we will not exceed the minimum estimations above. Source: Parrot Website https://www.dronepartspro.com/products/parrot-ar-drone-2-0-1500-mah-high-density-battery?utm_medium=cpc&utm_source=googlepla&variant=24538528326