Normal voltage drop

"Robert M. Gary" wrote:

It's interesting that if I take the alternator and regulator to the
bench I can hold 100amp without dropping below 14v. I guess the
in-airplane application is a lot different than the bench environement.


Oh? Well that points to a poor connection between the alternator
and the battery. It could be the hot side, or my favorite topic:
Bad Grounds. I suffered from the hot connection being loose on a
borrowed 91 CRX, on the way to a funeral. I hung a voltmeter on the
dash and noticed I was hardly gaining despite going at 60 mph. (I'd
run the battery down in traffic with headlights and blower on...)

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

Since working on a running engine with a big people-eater spinning
on the front never appeals to me; try this. Run it for a while; shut
it down. Start feeling connections back to the battery. When you
hit the bad one, you'll burn your fingers. (Trust me...)

If all joints are cold; start checking grounds. Or rather, inspect
and clean them. Alternator bond, if any. Engine to frame. Regulator
grounds. You name it.
--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

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