Normal voltage drop

On Wed, 29 Dec 2004 00:08:40 +0000 (UTC), David Lesher
wrote:

snipped for length, not for content.

You should be getting 14.4vdc to charge the battery; 13.8 is the
oft-quoted static voltage of the "12 volt" battery.

Technically, the voltage to "charge the battery" should be determined
by the aircraft manufacturer's maintenance manual. Ideally, the
voltage should be determined by the data presented by the manufacturer
of the specific battery installed.

For instance, Concorde recommends 13.75 v 90 degrees F, 14.0-14.2 v
@ 50-90 degrees F, 14.75 v 50 degrees F based on battery operating
temperature.

http://www.concordebattery.com/produ...r%20manual.pdf

The numbers for a Gill flooded-cell battery can be found within:

http://www.gillbatteries.com/battery...ice_Manual.pdf

Another interesting sidenote, is that while Concorde recommends 14.4 v
for constant potential charging on the bench for their flooded-cell
batteries, 14.1 v is recommended for the valve-regulated RG batteries.

Depending on how and where an aircraft is being operated, a bus
voltage of 14.5 v (recommended by several airframe manufacturer's) or
even 14.4 v can drastically shorten the life of both flooded-cell and
"sealed" batteries. Trip/leg length/time is also a factor. RG
batteries seem to be more sensitive to high bus/charging voltages, in
my experience.

The open-circuit or "static" voltage of the typical fully charged "12
volt" lead acid aircraft battery is usually close to 13 v, 26 v for a
"24 volt" battery, however, open-circuit voltage does not necessarily
reflect the state of charge or the amp/hour capacity present.

Regards;

TC

snip