nuckollsr(at)cox.net
Guest
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 Posted: Fri May 05, 2006 6:30 am Post subject: Alternator set point |
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At 05:58 PM 5/4/2006 -0400, you wrote:
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Good Afternoon Dave,
I have set one for 14.2. That was on the advice of the Concorde battery
folks and the manufacturer of the solid state regulator used on the airplane.
It seems to have worked very well for the last two hundred hours or so that
have been put on the airplane since the installation was made.
Happy Skies,
Old Bob
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Good point. When one considers the physics, practical applications
and variables that affect service life of batteries, the set-points
selected for aviation charging systems of 14.25/28.5 volts has
stood us well for decades. Yes, there are data sheets for EVERY
battery where EVERY designer/manufacturer has offered his/her
recommendations for squeezing the most life from their particular
product. Bottom line is that there are service stresses with far
greater influence on the battery's service life than the fine
tuning of bus voltage. 14.2 has been used with lead-acid technology
batteries since day-one and while setting one to run at 14.6 or higher
is recommended by some and not-recommended by others, in the final
analysis, it doesn't make a noticeable difference in most cases.
I think I wrote some years ago about discovering that the alternator
on my GMC Safari was running 15.2 volts! It had been at that voltage
for a very long time and I left it alone as an experiment. I was running
a 33 a.h. Panasonic RG battery at the time. I still got about three years
service from the battery . . . so I have a single data point experiment
that suggests that a startlingly high bus voltage did not portend
imminent doom for the battery.
Higher than 14.2 will RECHARGE a battery faster after start up
but is unnecessarily high for bringing a lead-acid battery
up to 100% capacity. ALL lead-acid technology batteries will
achieve 100% of charge at room temperature at 13.8 volts
charging potential. 14.2 is a compromise between long life at
float and rate of recharge after the engine starts. Higher than
14.2 pre-biases any form of ov protection device closer to it's
trip point and increases the possibility of nuisance trips.
Bob . . .
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