Message-ID: <000501bff502$00419160$50a10f3f@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 16:59:11 -0700
Mime-Version: 1.0

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To David Jones, re: Makita drill battery.

Dave, that battery is most assuredly a nickle cadmium (NiCad) unit and you
don't want to try charging it from your alternator. Lead-acid batteries,
such as your primary battery, due to their charging characteristics, may be
"float-charged" by directly connecting them across the alternator bus. Just
like the battery in your car. Unfortunately, NiCads are much more difficult
to charge safely - with the operative word here "safely". Try to
float-charge a NiCad and, depending on it's internal temperature (which will
vary with how much current the bus is dumping into it), it can suffer from a
condition referred to as "thermal run-away". If this hapens when the battery
is in your airplane, you can have a catastrophy on your hands. A NiCad in
thermal run-away can melt it's way right through the bottom of the
fuselage - if you're lucky! If unlucky, you will have a fire on your hands.
In the least, if the battery only ruptures from the heat, the electrolyte
isn't something you want loose in the airframe.

Unless you use a charger specifically designed for a NiCad, which adjusts
the current depending on temperature feedback from a special sensor in the
battery, stick with lead-acid batteries for your back-up unit.

Dan Schaefer

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