Message-ID: <000501bff538$10809860$566b1b3f@oemcomputer>
Reply-To: "dfs" <dfs@gateway.net>
Reply-To: lancair.list@olsusa.com
From: "dfs" <dfs@gateway.net>
To: "Lancair List" <lancair.list@olsusa.com>
Subject: Backup Battery KISS
Date: Sun, 23 Jul 2000 23:25:36 -0700
Mime-Version: 1.0

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Regarding my earlier post on NiCad vs lead-acid batteries and the vagaries
of their charging requirements, I had meant to add my credentials to
validate the assertions however, my wife called me at that moment for a
"honey-do" and I didn't have the time.

So, just so you know I'm not blowing smoke - one of the many and varied
systems I had design responsibility for at Rockwell on the B-1 (A & B) was
the main batteries and their chargers. The B-1, being almost entirely an AC
aircraft, had only two primary batteries, but if they didn't function, you
couldn't even get into the airplane because one opened the hatch and ran the
entry ladder down and the second was required in certain flight conditions
as a safety-of-flight power back-up source! The NiCads were only about 6 AH
capacity each.

Initially, we used NiCads as they were all the rage with the Air Force at
the time. They were mighty expensive as were their chargers and the Air
Force was paying a high price, annually, just for maintenance. Because of
this, the last program I completed before I retired from Rockwell (actually
Boeing by that time) was the conversion of the fleet to maintenance free
Sealed Lead-Acid Batteries (SLAB's) and of course, new chargers.

The NiCad chargers were very special beasts that were devilishly complex
and, even in the days of $600 toilet seats, expensive (close to $20,000 a
piece!). The batteries weren't cheap, either - like $7500 per!

For all these reasons, and more, it was decided to change to SLAB's (15 -20
AH each) with new chargers. The chargers were nothing more complex than
simple regulated and current limited DC power supplies and the batteries
provided nearly 5 times the capacity - particularly important for the
safety-of-flight back-up system. Plus, when the batteries were worn out,
they were merely discarded to the recycle dump saving the AF mounds of
maintenance dollars. Further, the entire system (two batteries and two
chargers) cost less per airplane than about half of a NiCad charger!

And we never had to worry about a NiCad thermal run-away, either.

Dan Schaefer

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