Design of a Village Battery Charger
Electrical Engineering
Problem Statement
In rural Ghana, approximately 80% of households lack access to electricity. Even those lucky
enough to tap into the main grid suffer from frequent and extended rolling blackouts, making
the reliable supply of power a development priority. Energy is a key component to meet many of
the Millennium Development Goals, such as improved health care, education, and food security.
With electricity, children are able to study at night, medical procedures (such as delivering
babies) can be done much more safely and effectively, and refrigerators can be used to store
vaccinations and food that would otherwise rot.
You are an Electrical Engineer working for an organization in Ghana that aims to provide a
reliable and affordable source of energy for Changnayili, a village that does not have access to
the electricity grid. Your organization would like to create a market for 12V DC batteries in the
village to be used for powering lights, refrigerators (including a vaccine refrigerator for the local
clinic), and entertainment such as stereos and televisions for football games.
In the village, there is an entrepreneur with an existing 8hp diesel engine coupled to a corn mill
on one side and a cassava grater on the other (Figures 1 and 2). The machines can only be run
one at a time using a belt drive. All of the equipment is cemented into the floor and often breaks
down because it was not aligned properly during initial installation.
Figure 1: Engine and Cassava Grater
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Figure 2: Engine and Corn Mill
In your design choices, consider the following requirements:

Technical Considerations: New batteries cannot be charged past 12V (or they may
explode!) and have a capacity of 150Ah. Your market survey has shown that you expect a
minimum of 5 batteries to be dropped off for charging a day.

Charging Dead Batteries: Many villagers already use disposed car batteries to power
black and white televisions, and will be a primary target market for your battery charger.
They have to replace the electrolyte with each charging to get them to last approximately
one week. When charged to only 12V, these batteries will only last 10 minutes so they need
to be charged until the electrolyte boils for 10 minutes (roughly around 14.5V). Since a
football game lasts longer than 10 minutes, you will have very angry customers if they pay to
have their batteries charged and they don’t even make it to half time! Expect a mix of new
and old batteries to be dropped off for charging at any given time.

Cost: Cost is a major factor impacting accessibility of the technology to rural householders.
Your organization has recently conducted an assessment to determine how much each
household would be willing to pay for battery charging. According to this research, a
customer would not be willing to pay more than $1 to have a battery charged, and would
expect it to last at least one week.
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Project Scope
In a town about an hour away there is an automotive shop that also charges new batteries for
$1.50. The entrepreneur would like to be able to charge both new and dead batteries
simultaneously. Your job is to design a simple electrical circuit that enables the user to know
when a 12V battery is fully charged so that you can remove them from the charging system and
allow the dead batteries to continue to charge.
In your design, you must decide whether you would like to charge the batteries in series or
parallel. Note that with the parallel configuration you will need to install a resistor after the
alternator in order to decrease the voltage to 12V for the batteries. If you choose the parallel
configuration you will need to calculate the value of the resistor needed to have a 12V drop
across the batteries.
current (A)
current (A)
12 V
12 V
12 V
12 V
12 V
24 V
12 V
Parallel
Series
Provide a report to Engineers Without Borders outlining your approach to the problem, your
conclusions, and any further recommendations you feel should be considered.
You should organize your report into the following sections:
 Executive Summary
 Problem Identification (include Constraints and Criteria)
 Ethical Considerations about the Project
 Proposed Solution and Justification
 Expected Impact on the Community
 Conclusion and Recommendations
 Appendices (include Calculations)
 References
 Technical sketches or drawings
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