Solar Charging Batteries

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Solar Charging Batteries

• Lauren Perry
• MEE 573 Renewable Energy Systems
• April 24, 2002

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Outline

• Purpose
• Charging concerns
• Battery types
• Chargers
• Solar cells
• Equations
• Charging program
• Solar charger example
• Conclusions

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Purpose

• Using solar power to charge batteries
• Camping
• Remote areas
• Small applications
• Flashlights
• Radios
• Calculators

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Charging Concerns

• Battery type
• Reverse current flow
• Overcharging battery
• Voltage (V P/I)
• Number of batteries vs. charging time

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Battery Types

• Rechargeable
• Lead Acid, NiCd, NiMH
• NiMH (Nickel Metal Hydride)
• Provide more power than NiCd
• Improved energy density longer run times
• Lacking in toxic Cd
• Memory not a concern

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Energizer NiMH Rechargeable
Battery stuff - for Energizer, NiMH
rechargeable Voltage 1.2 V nbat
1.2/(14.12) 1.2 A-hr capacity/(14 hrs at 120
mA max) ButtonName questdlg('What type of
battery do you want to charge?', ... 'Battery
Type', 'C or D','AA','AAA','C or D') switch
ButtonName case 'C or D' cap 2.200 Ah
max_chg_rt .440 A end
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Battery Charger Schematic
Solar Cell Array
Current Limiter
Diode
Capacitor
2 NiMH batteries connected in series
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Siemens Solar Module SM10
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DataSheet
For photovoltaics - Siemens Solar Module
SM6 max_power 10 W Eref 16.3 Volts Iref
.61 Amps A_pv .36.330 m2 mu
-.000238 1/C NOCT 45 C Tref_STC 25
C nref 10/(1000A_pv) taUl (NOCT - 20)/800
Cm2/W
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Equations

• Loop while batstore lt battery capacity

Photovoltaics nc nref mu((Ta -
Tref_STC) IttaUl(1-nref)) Powerout
ncItA_pv Eout 4 Volts - add a
capacitor to get down to 4 volts Iout
Poweroutnbat/Eout Amps if Iout gt
max_chg_rt This limits the current to the max
charge rate Resistor Eout/(max_chg_rt)
ohms Iout max_chg_rt Amps end
batstore batstore Iout1 Amp-hours
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Matlab User Choices
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Matlab Output
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Universal Solar Battery Charger

• SPECIFICATIONS
• Type mA/Hour Pieces
  Sunlight Hours
• AAA(UM-4) 180mA 2
  1-2
• AA(UM-3) 500mA 2
  3-4
• C(UM-2) 1000mA 2
  6-8
• D(UM-1) 1500mA 2
  9-12
• Recharging time may vary according to the
  strength of the sun and level to which the
  batteries are discharged.
• Price 24.95 S/H

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Conclusions

• NiMH battery type best for application
• Solar not practical for large batteries or large
  quantity of batteries
• Charging time reasonable

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Questions?