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Archiver > TMG > 2003-06 > 1054845556


From: Richard Brogger <>
Subject: Re: [TMG] Comment on UPS
Date: Thu, 05 Jun 2003 15:39:16 -0500
References: <1737332.1054820707738.JavaMail.nobody@wamui04.slb.atl.earthlink.net>


Hi Darrell,

I will add a comment to your comments about comments. <g>

I agree with everything that you wrote except the last line. That one
is a maybe. Buy a replacement battery and it will usually be special
order and expensive while the UPS is local and often at a special
price. It can be cheaper to buy a new UPS for $74.95 on special than
to order the $69.95 replacement battery and pay shipping.

Actually, one should make sure that the price for a UPS includes
shipping. The battery makes them heavy and shipping can drive the cost
up quite a bit when the UPS is not purchased locally.

I also have a question. My UPS has a 12 volt battery and I do have 12
VDC available. However, the instructions specifically warn against
using external sources. I suspect that the reason is that the built-in
charger would fry if it tried to charge large external batteries but I
am only guessing. Do you know the actual reason?

Richard Brogger

Darrell Martin wrote:
>
> Greetings:
>
> Two more comments, or comments on comments [grin].
>
> First, whether your laptop battery will act as a UPS depends
> on a few things, but a fairly new battery in good condition
> in a fairly new laptop will almost certainly be fine. The
> recommendation about using a surge suppressor anyway is a
> good one. If you have very large numbers of "power events"
> where you will be using your laptop it would probably be a
> good idea to get a small UPS *anyway* and plug the laptop
> into that. That's the "belt and suspenders" ("belt and
> braces" to some) approach.
>
> Second, there are two basic types of UPS's when it comes to
> whether they have to "switch" to battery power. The idea is
> very simple, but the terminology may differ. Some UPS units
> will only switch from line power to the battery when certain
> conditions occur. Typically, there is a voltage range that
> is considered "acceptable", by which is meant that the UPS
> can regulate the output voltage and therefore does not run
> off the battery during relatively minor brownouts (voltage
> sags). This can protect you from "constant" voltage alarms
> and wear and tear on the UPS battery, and is particularly
> useful in areas with unusually unreliable power.
>
> The other type runs off the battery constantly. These tend
> to be useful for high-end systems which might be sensitive
> to power loss for even a few milliseconds. Almost all PC power
> supplies have some kind of "buffer", usually a capacitor of
> some kind or the equivalent but sometimes a small built-in
> battery, to handle such quick power losses as a changeover
> from line to battery power, so I would not recommend that a
> typical TMG user should look at this as an important feature.
> Note that such types of UPS also have a range of acceptable
> voltages, not for the purpose of switching but for issuing
> alarms and initiating automated shutdowns.
>
> BTW, automated shutdown can be a feature on either type.
> Shutdowns are managed by software on the PC, with a wired
> connection, typically through USB or a serial (COM) port. A
> typical TMG user is not likely to use automated shutdown
> very much, but if you run programs unattended for any reason
> this feature is a *must*.
>
> Another useful feature on a UPS is a replaceable battery.
>
> Darrell
>
> Darrell A. Martin
> a native Vermonter in exile in Illinois
>


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