Message-ID: <004201bff91e$c72e5220$7f6b1b3f@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 Electrical Power
Date: Fri, 28 Jul 2000 22:35:15 -0700
Mime-Version: 1.0

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Sorry Bill, you've skipped a decimal point in your figuring the Ampere Hour
(AH) rating af a battery. Figuring your way, would make it a 120 Ampere Hour
battery instead of 12 AH!

A 12 AH battery will theoretically deliver 12 amperes for ONE hour - that's
what the Ampere Hour rating means. Where the 10 hour figure comes from is
the fact that most batteries will only deliver the equivalent amount of
energy, e.g., 12 Ampere Hours, if discharged over a period of 10 hours (or
at least, some reduced rate). If discharged at the full 12 amperes, most
lead-acid batteries (and many other types as well - such as NiCads) will
deliver only a fraction of the full rating. This is because high discharge
rates will form gas bubbles directly in contact with the plates effectively
blocking (insulating) some part of the charged medium. Take the energy out
at a lower rate, such as 1/10th of 12 amps, or 1.2 amps, and the bubbles
don't form and you'll get the full 12 AH stored in the battery.

The bottom line is: A 12 AH battery will deliver 1.2 amps for ~10+ hours, 12
amps for maybe 45 minutes and it goes down from there.

Dan Schaefer


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