Hi,
I'm using a 700W UPS (localy made) with a 120 Ampere battery to run
three ceiling fans (150W each), a tube (40W), and my laptop (70W?) and two
energy savers (18W each) to cover load shedding time which is mostly for one
hour several times a day. The problem is if all tree fans are running for
some time, they begin to slow down considerably. Is the battery responsible
for this or the UPS.
If I add another battery in parallel will this solve the problem. I intend
to add another fan to this. Also is there a way to test what is the actual
strength of the UPS? It is common here to sell UPS that are lower in power
than what is printed on them.

Thanks

The 700 W rating is the maximum load that can be used from the UPS
without any damage to it, or it with it being over-loaded. Normaly, the
maximum load should not exceed about 60% of the maximum capacity of a
UPS.

In the instruction manual for the UPS, they usually give a chart of how
long it will supply power with different loads. The effect of the load
may not be exactly linear because the load is being run from an
inverter. This inverter itself uses a certain amount of base current to
operate. It's efficiency may not be very linear.

In theory, a 120 Amp Hour battery should be able to put out 120 Amps for
one hour. Normaly, when a battery is under load, when the voltage of
the battery has decreased to about 10% below the nominal rating of the
battery voltage, the battery is considered weak.

When evaluating a battery, make sure that you know if the Amp rating of
the battery is the maximum output load, or it is the maximum Amp Hours.
There will be a difference in its performance.

A standard 12.5 Volt battery would be considered discharged when its
output has decreased to 11.36 Volts. This is when the battery is under
its nominal rated load. For most gel and lead acid batteries, the
maximum normal load is considered to be 1/4 of the Amperage rating of
the battery. This would be the load rating best for testing the battery,
and for having the most efficient use from it.

If you have a battery rated at 120 Ampere hours, in theory it should be
able to put out 120 Amps for 1 hour. In reality, if you did this, the
battery would be under severe stress. A 120 Ampere hour battery should
be able to operate a 10 Ampere load for a period of 12 hours.

In a UPS, there are a number of electronic circuits that have to be
operated by the battery. There is also the inverter output driver
itself. These all consume some of the battery power. It may be as much
as 10% of the available power when it is on the battery.

A very simple example of evaluating a UPS would be to look in the
instruction manual. If it indicates that the UPS can run for 15 minutes
at the full load, then it should be able to run for at least 30 minutes
at 1/2 load.

In calculating your load, you are asking about 600 Watts from the UPS.
This is about 90% of its load capacity. Without the internal load of the
UPS's electronics, this works to 50 Amps at 12 Volts for the battery. If
I add 5 Amps for the electronics, I get 55 Amps. If the battery is rated
at 120 Ampere hours, you should be able to get at least 2 hours of
operation.

Personaly, I would not share the same power source for a computer with
other appliances, and especially if they are reactive devices such as
with a motor. The only thing I would have on the UPS is the computer,
the monitor, and the printer if the UPS can take the load. For lighting
and the extras, I would use a separate UPS.

For the emergency lights here in my office, I have a 1200 Watt UPS
running a few compact fluorescents with a total of less than 40 Watts.
With the battery power I have with it, this light will run for over 24
hours.


--

JANA
_____


"Procrastinator71" wrote in message
...
Hi,
I'm using a 700W UPS (localy made) with a 120 Ampere battery to
run
three ceiling fans (150W each), a tube (40W), and my laptop (70W?) and
two
energy savers (18W each) to cover load shedding time which is mostly for
one
hour several times a day. The problem is if all tree fans are running
for
some time, they begin to slow down considerably. Is the battery
responsible
for this or the UPS.
If I add another battery in parallel will this solve the problem. I
intend
to add another fan to this. Also is there a way to test what is the
actual
strength of the UPS? It is common here to sell UPS that are lower in
power
than what is printed on them.

Thanks

Running batteries in parallel is a bad idea. Think of what will happen if
their voltages don't match. If you do such a thing, you need to put diodes
in series with each.

I would suggest getting another SPS.

"William Sommerwerck" wrote in message
...
Running batteries in parallel is a bad idea. Think of what will happen if
their voltages don't match. If you do such a thing, you need to put diodes
in series with each.


Some car batteries are connected in parallel. Especially larger trucks with
diesel engines.

Mike

Michael Kennedy wrote:
"William Sommerwerck" wrote in message
...
Running batteries in parallel is a bad idea. Think of what will happen if
their voltages don't match. If you do such a thing, you need to put diodes
in series with each.


Some car batteries are connected in parallel. Especially larger trucks with
diesel engines.

Mike




Those normally use a battery isolator which is really just a couple of
large diodes. Most RVs and larger boats have a setup like that too.

"JANA" wrote in message
rvecommunications...
The 700 W rating is the maximum load that can be used from the UPS
without any damage to it, or it with it being over-loaded. Normaly, the
maximum load should not exceed about 60% of the maximum capacity of a
UPS.

In the instruction manual for the UPS, they usually give a chart of how
long it will supply power with different loads. The effect of the load
may not be exactly linear because the load is being run from an
inverter. This inverter itself uses a certain amount of base current to
operate. It's efficiency may not be very linear.

In theory, a 120 Amp Hour battery should be able to put out 120 Amps for
one hour. Normaly, when a battery is under load, when the voltage of
the battery has decreased to about 10% below the nominal rating of the
battery voltage, the battery is considered weak.

Most battery manufacturers specify Ah capacity for the 10 hour discharge
rate - a 120Ah battery loaded at 120A will be discharged in somewhat less
than 1 hour.

On Thu, 5 Jun 2008 20:51:33 +0100, "ian field"
wrote:


"JANA" wrote in message
ervecommunications...
The 700 W rating is the maximum load that can be used from the UPS
without any damage to it, or it with it being over-loaded. Normaly, the
maximum load should not exceed about 60% of the maximum capacity of a
UPS.

In the instruction manual for the UPS, they usually give a chart of how
long it will supply power with different loads. The effect of the load
may not be exactly linear because the load is being run from an
inverter. This inverter itself uses a certain amount of base current to
operate. It's efficiency may not be very linear.

In theory, a 120 Amp Hour battery should be able to put out 120 Amps for
one hour. Normaly, when a battery is under load, when the voltage of
the battery has decreased to about 10% below the nominal rating of the
battery voltage, the battery is considered weak.

Most battery manufacturers specify Ah capacity for the 10 hour discharge
rate - a 120Ah battery loaded at 120A will be discharged in somewhat less
than 1 hour.


If they are working to US SAE specifications it is 20 hour discharge.

On Thu, 5 Jun 2008 14:59:07 -0400, "Michael Kennedy"
wrote:


"William Sommerwerck" wrote in message
...
Running batteries in parallel is a bad idea. Think of what will happen if
their voltages don't match. If you do such a thing, you need to put diodes
in series with each.


Some car batteries are connected in parallel. Especially larger trucks with
diesel engines.

Mike


Actually the batteries are in series to run the starter motor, and
isolated otherwise.

Procrastinator71 wrote:

Hi,
I'm using a 700W UPS (localy made)

Just out of interest, of what value is the information "(localy made)" sic
when you don't mention what part of the world you live in ?

Or is it the 'world' called the USA ?

Graham

On Thu, 13 Nov 2008 20:08:43 +0000, Eeyore
wrote:



Procrastinator71 wrote:

Hi,
I'm using a 700W UPS (localy made)

Just out of interest, of what value is the information "(localy made)" sic
when you don't mention what part of the world you live in ?

Or is it the 'world' called the USA ?

Graham

I'd say he made it himself...