bakerocb
Joined: 15 Jan 2006
Posts: 727
Location: FAIRFAX VA
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 Posted: Mon Jul 16, 2012 3:59 am Post subject: weights and balances- battery |
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7/16/2012
Hello Keith, You wrote: "My 10 year old Concorde battery ( CB35) finally
gave up last winter........"
10 years old -- Wow, how did it "give up"? When a car battery finally
"gives up" the scenario is usually that one can not get the starter to crank
the engine. There is the usual inconvenience of getting a jump start, then
driving to a battery supply source, replacing the battery, and proceeding
on one's merry way. No great harm done.
When an airplane battery can no longer crank the engine that battery has
long since previously lost its capacity to supply electrical power to
operate any essential electrical devices in the airplane for any significant
period of time should the alternator fail. If inability to operate any
essential electrical devices for the period of time needed to get the
airplane safely on the ground is unacceptable then the pilot has a much more
serious problem than just getting a jump start.
In that "inability to operate" scenario, flying with a clapped out battery
(which can provide no electrical reserve) is analogous to flying with
essentially no fuel reserve and expecting to always being able to safely
land and taxi to a fuel source before the propeller stops cooling the
pilot -- not good.
So using successful engine cranking as the sole indicator of an airplane's
battery's health (reserve capacity) can be deleterious to the pilot's
health. What can one do to ensure that there is sufficient electrical
capacity remaining in the battery for
essential / endurance needs when just cranking the engine is not a good
indicator of battery actual capacity? There are two methods:
1) Use a battery capacity tester to determine the reserve capacity of the
battery. Here is just one example:
http://www.gillbatteries.com/capacitytesters.aspx
2) Just arbitrarily replace the airplane's battery at some periodic
interval -- say every two years?
Bob Nuckolls, our great electrical guru, has touched on this subject in his
postings on the Matronics aeroelectric-list many times. His thoughts on the
subject can be researched through the list archival search capacity.
http://www.matronics.com/Navigator/?AeroElectric-List
His Jun 09, 2005 posting on battery testing gives his philosophy on
preferring this second course of action.
OC
================================================================================
From: Keith.Miller(at)esa.int
Sent: Monday, July 16, 2012 3:59 AM
To: kis-list(at)matronics.com
Subject: Re: weights and balances- battery
Jesse
My 10 year old Concorde battery ( CB35) finally gave up last winter and I
replaced it with an Aerovoltz Lithium Iron phosphate battery weighing just
3Lbs, So far It has spun up the engine without any problems , but only time
can tell if its as reliable as my old lead acid , this solution moved my
Cof
G forward without any need to rewire or move hardware.
Keith
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