Subject: Generator 1 of 7



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(3539)   Sun 21 Jul 91 23:22                             
By: Don Kulha
To: All

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Build Your Own 12 VDC Engine/Generator

by Richard Perez

This small, easy to build, generator is the answer to a burning AE 
question.  What do we do when the sun doesn't shine, the wind 
doesn't 
blow, and the creek dries up.  This generator is a back up power 
source for times when our AE sources don't meet our demands.  It 
is optimized to do only one thing-- properly recharge batteries.

Engine/Generator Overview
Before we actually discuss the construction of this 
engine/generator, 
let's examine the job it is designed to do.  It is the nature of 
this task that determines the various design decisions we need to 
make when constructing this back up generator and its control system.

Source Capacity
Every AE system should have at least one power source capable of 
recharging the batteries at between C/10 to C/20 rates of charge.  
For example, a battery pack of 700 ampere-hours periodically needs 
to be recharged at a minimum of 35 amperes (its C/20 rate).  To 
figure 
the C/20 rate for your pack simply divide its capacity in 
Ampere-hours 
by 20.  The resulting number is the C/20 rate in Amperes.  The C/20 
rate is the minimum necessary for equalizing charges.  If the 
batteries 
cannot be equalized they will fail more rapidly.

Power Source Control
Most energy sources that charge batteries need to be controlled.  
If the charging source is not controlled, then the batteries may 
be overcharged or charged too rapidly.  They can be ruined.  The 
most common method of control is voltage regulation.  This works 
fine in cars and in batteries with shallow cycle, float service.  
Voltage regulation alone is not enough for deeply cycled batteries.  
They must also be current regulated to prevent too rapid recharging.

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