Re: NTLK Other - Backup Battery warning

From: Leland Jory (ljory@newted.dyndns.org)
Date: Fri Dec 03 1999 - 09:25:22 EST


Frank said:

It is correct that "dead" batteries show almost full voltage. The reason is
that usually they are measured when they don't have to supply any power.

My reply is: How come I've tested hundreds (if not thousands) of "dead"
batteries, ALL of which registered 0V (or thereabouts, I'm smart enough to
realize that a 3V battery measuring about .5V is as close to dead as makes
no nevermind). I've never had a "dead" battery measure any significant
amount of voltage.

Maybe I'm ignorant of something, but it seems to me that "dead" batteries
will show as "dead" to a voltmeter when measured out of circuit.

Remember, voltage is simply the electrical potential in a device (akin to
water pressure in a water tower). You can measure water pressure without
running the tap in your sink, similarly you can measure voltage without a
load. As the battery is used more and more (the water level in the tower
gets lower and lower), the voltage (pressure) drops in direct proportion.
Eventually, there is not enough voltage (pressure) to power your device
(like a water wheel). Keep in mind that this is a simple analogy designed to
illustrate a specific aspect of electrical theory and, as such, does not
carry into other aspects of such theory.

Please, illuminate me if I am misinformed.

Leland Jory

"Newton users swear by their PDAs. WinCE users swear AT their PDAs."

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