Tim Villabona
6.131
Final Project Proposal
October 30, 2008
A Car Battery Charger
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Description and Motivation
Being a busy MIT student, the frequency that I drive my car has gradually decreased
to almost biweekly. This fact, plus the increasingly cold weather, means that my battery often dies between drives–a newer battery would probably be able to withstand
the punishment, but this battery is several years old. Whenever this happens, I have
to walk over to the MIT Police to borrow their portable battery/jump starter. This
is often a source of frustration, especially if I’m with friends or on a tight schedule
about getting somewhere. I would like to design a circuit that solves this problem,
so I neither have to buy one myself nor borrow MIT Police’s.
Originally I had wanted to develop a system that could be hand or pedal powered, charging up a capacitor that could store sufficient charge and supply enough
current to the starter itself, giving the energy needed to start the vehicle. However,
I took a quick look at car batteries and discovered that they are rated to deliver
several hundred amps for those few seconds of cranking the car engine. Quickly I
decided that that would be an unfeasible idea–which is why I suppose I haven’t seen
hand-powered car starters on the market.
I suppose that the next best thing would be a battery/circuit that can be charged
at the wall, and then connected to the car battery itself to charge it sufficiently to
start the car, from where the alternator would take over to continue charging the
battery. Some useful features I can add to this are:
• Automatic current regulation to optimally and safely charge the battery
• User notification (LED/sound) when sufficient charge to start the car has been
reached
Overall, I see this circuit as conceptually simple, yet I’m definitely not sure of what
exactly I’ll need, which is why I think it’s complicated enough to be a good 6.131
final project. I think it would be best to keep a modular architecture, so that I can
first design it to work off of a serial combination of batteries. Then, if I have enough
time, I can design something to charge rechargeable batteries off the wall, which can
then be connected to what I already designed.
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Block Diagram
The block diagram is pictured below:
This is a very high-level conceptual schematic of what I would like my circuit to
include. I may or may not require additional modules.
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Scope and Components
I believe that this will not require too specialized components. At its most complex
realization, this would be something that runs off a wall to charge batteries, which
are then connected to a car battery and charge it optimally, and then notifies the
user when sufficient charge to run the starter for a few seconds is created.
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Timetable
A first draft of my rough timetable:
• Nov. 10: Arrive at a detailed model with calculated values, order parts if
needed.
• Nov. 17: Assemble and test at the breadboard/solder PCB level.
• Nov. 24: Safety buffer week.
• Dec. 1: Make the assembly ‘nice’: custom PCB? Plastic housing?
• Dec. 8: Checkoff!
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