[Tfug] FTGH: APC Back-UPS Pro 650

[johngalt1]

----- Original Message ----- 
From: "Jeremy D Rogers" <>
To: "Tucson Free Unix Group" <tfug at tfug.org>
Sent: Monday, April 23, 2007 9:30 AM
Subject: Re: [Tfug] FTGH: APC Back-UPS Pro 650


> On 4/20/07, Sean Warburton <> wrote:
>> I'm sorry! I didn't know a series/parallel discussion would ensue...Here 
>> was
>> how I found it: the positive went somewhere into the unit, and the 
>> negative
>> went directly to the positive in the second battery. the negative from 
>> the
>
> Umm.. so they were in series, not parallel. So if you added more in
> series, you would increase the voltage. That doesn't sound like a good
> idea.

Actually, it is a good idea. UPSes are rated by power rating (VA, or KVA) A 
formula for power is P=IV, where I is current and V is voltage. Another 
formula for power is P=I^2 R

As someone else in the thread pointed out, if increase teh voltage, you 
lower the current ( I ). Then, I^2R (power) losses are reduced.  As a 
result, power loss due to heat (resistance ( R ) in the wiring, connections 
and circuitry) will be less for higher voltage in the battery bank.

Low end UPSes typically use 24V battery storage. However, when you look at 
the 2KVA-3KVA range, they use 48V battery packs to reduce lossses. In higher 
capacity UPSes, they design the battery voltage to be even higher.

Another way to look at it is: If your UPS uses a higher battery voltage, the 
transformer used to boost the voltage to 115VAC will be smaller and more 
efficient. The transformer (or inverter really), will not have to boost the 
voltage as much, and pay for that difference with a high current.