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Lithium Polymer Charging
Through Conduction
Breaking down the Procedure
A.R. Drone 2.0 1000mAh Battery
Back Label on our Battery
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.
• 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.
Battery
Damage
Overcharging:
Cells over 4.2V or 12.6V (3x4.2V/cell) are
‘overcharged’.
-Overcharging can significantly decrease
lifespan of the battery and potential
explosion.
Undercharging
- Reducing the cells under 3V
decreases battery lifespan.
- Reducing to 2.5V causes
permanent and sometimes fatal
damage.
https://en.wikipedia.org/wiki/Lithium_polymer_battery#/media/File:Expanded_lithiumion_polymer_battery_from_an_Apple_iPhone_3GS.jpg
Temperature
- 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.
Rapid Charging
- Can cause swelling similar to overcharging
- 1C Charging Rate standard.
- Causes rapid temperature increase.
Damaged Lithium Polymer Battery – Swelling caused
by overcharging.
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?
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.
It is possible to safely charge
from
~15-20%
To
~80%
If temperatures remain under 65
Celsius.
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 outputvoltage 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/41938/230vac-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-densitybattery?utm_medium=cpc&utm_source=googlepla&variant=24538528326