The Design:
According to me, assembling the entire
station using ready made units would be a lot better idea instead of
building the individual circuits. This approach will be quicker, easier
and will avoid many difficulties which are normally a part of
manufacturing processes.
The cell phone charger requirement can
be solved by procuring and installing 20 nos. ready made cell phone
chargers and by connecting their mains inputs in parallel to a small
solar inverter.
Charging a cell phone Li-Ion battery
can be very critical and requires high grade smart chargers with auto
shut-off features for charging them safely.
Manufacturing such smart charger requires a lot of expertise and experience, so I won't recommend making these units.
Instead 20 nos. second hand cell phones may be procured (example NOKIA1280) and may be used as Li-Ion battery holders cum chargers.
All cell phones have a built-in smart charger which charge the involved battery with utmost care and automatically shut off the process when the charging is completed. The display provides the necessary information with a beep sound once the charging is completed, so that's a cool way of charging the Li-Ion batteries without taking any risks.
The cell phones may be used normally when they are not being employed for charging the above batteries.
Manufacturing such smart charger requires a lot of expertise and experience, so I won't recommend making these units.
Instead 20 nos. second hand cell phones may be procured (example NOKIA1280) and may be used as Li-Ion battery holders cum chargers.
All cell phones have a built-in smart charger which charge the involved battery with utmost care and automatically shut off the process when the charging is completed. The display provides the necessary information with a beep sound once the charging is completed, so that's a cool way of charging the Li-Ion batteries without taking any risks.
The cell phones may be used normally when they are not being employed for charging the above batteries.
The following block diagram illustrates
the different stages that may be employed for installing 20 solar
powered cell phone station:
The first four blocks represent a
standard solar electrification set up. The solar panel voltage is first
tailored to the required battery voltage through a solar
charger/controller module.
The output from the solar module is then fed to an inverter battery for charging it.
The charger/controller automatically cuts off the charging of the inverter battery when it's fully charged and resumes when it reaches the under charge threshold level.
The battery is used for driving the inverter whenever required.
The output of the inverter is used for charging the proposed cell phones and the Li-Ion batteries.
20 cell phones would roughly consume 20 to 30 watt hour of power, so a 100 watt inverter would adequately serve the purpose.
A 40 AH car battery is recommended here, which would happily satisfy the 5 day autonomy requirement.
The solar panel is not very critical here, a 60 watt panel having an open circuit voltage of 30V and a short circuit current of 3 amps will be quite suitable for the present application.
The solar charger/controller is the only equipment that may be manufactured at home. I have already discussed one such circuit in this article, which may be effectively employed for the present application (the transformer should be replaced by the solar panel terminals).
The output from the solar module is then fed to an inverter battery for charging it.
The charger/controller automatically cuts off the charging of the inverter battery when it's fully charged and resumes when it reaches the under charge threshold level.
The battery is used for driving the inverter whenever required.
The output of the inverter is used for charging the proposed cell phones and the Li-Ion batteries.
20 cell phones would roughly consume 20 to 30 watt hour of power, so a 100 watt inverter would adequately serve the purpose.
A 40 AH car battery is recommended here, which would happily satisfy the 5 day autonomy requirement.
The solar panel is not very critical here, a 60 watt panel having an open circuit voltage of 30V and a short circuit current of 3 amps will be quite suitable for the present application.
The solar charger/controller is the only equipment that may be manufactured at home. I have already discussed one such circuit in this article, which may be effectively employed for the present application (the transformer should be replaced by the solar panel terminals).
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