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UPS Backup calculation

Wharfedale EVO4.4 Speaker

music4mhell

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Hello Guys,

I just took ACT broadband, they can provide even during line cuts.

My TPLINK AC750 router has power supply of 12VDC/1A.

If i buy an UPS of 600VA, how long it can power up my router only (Nothing else is connected to the UPS).

I am not so good in Maths, plz guys help me out.
 

raghupb

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Depends on how much battery juice is there. 600VA is a measure of how many concurrent devices are drawing power.
Router wall wart will have an ac-dc converter. With some conversion loss and a fully charged battery you can expect it to be a long time for a single device. Wild guess 24 hours min assuming a small battery
 
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gilfredpaul

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I have four devices connected to my APC ups pro 1000

1. Digsol modem
2. AirPort Extreme
3. WD my cloud
4. TPLink switch box

For which roughly I get around 2 hrs backup.
 
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music4mhell

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Depends on how much battery juice is there. 600VA is a measure of how many concurrent devices are drawing power.
Router wall wart will have an ac-dc converter. With some conversion loss and a fully charged battery you can expect it to be a long time for a single device. Wild guess 24 hours min assuming a small battery

If power output is 600W then ?
 
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raghupb

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Hmmm ...
If the UPS is 600VA then actual power handling will be less in Watts.
If the UPS is 600W then the actual apparent power available is more in VA.
There is something called Power Factor (PF) or vaguely efficiency at play in all UPS and device power supplies too.

VA x PF = W
VA - Rating of UPS
PF - Power factor (number between 0 1nd 1) of efficiency in %
W - load that it can support

Most small UPS PF is between 0.5 and 0.8 (60% - 80% efficiency). Even though they claim > 80%, I would take it with a pinch of salt.

Lets take an example
APC Back-UPS 600 (relevant specs below)
Output power capacity - 360 Watts / 600 VA
Max Configurable Power (Watts) - 360 Watts
Battery Volt-Amp-Hour Capacity - 60
(really don't know how they specify this; as the common measure for battery is Amp-Hour at a nominal Voltage, not Volt-Amp-Hour; assuming it is a 12V battery then its capacity is 5Ah)

This UPS has a PF = 360/600 = 0.6 (60%)
Now for run time (from their own website)
Load Time
50W 40min
100W 25min
200W 6min
300W 2min

As you near the max rating in Watts, the run time decreases drastically.

Now lets take your device (router). It uses a wall-wart for AC/DC conversion. Wall warts can be good or bad. Most are not efficient, meaning a portion input power goes in heat.
At 12V/1.5A it is an 18W hog (gigabit Eth and hi-speed wifi; not exactly a power friendly combo); add wall-wart power loss of 7W. That bring it to 25W load.

On the above UPS example, you may get about 1.5 hours. On a home 850VA UPS with a larger battery (say 150Ah) you can get a much much longer run time. Not because of the UPS rating but beacuse of the battery.

Hope explanation this helps. This is the best I could come up with the available info.

Cheers,
Raghu
 
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krishnamurthy

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That particular model is highly inefficient. Anything less than 70% efficiency is a piece of junk. Having said that, many models of manufacturers that sell equipment less than 1 KVA rating are notoriously inefficient.
 
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music4mhell

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Hmmm ...
If the UPS is 600VA then actual power handling will be less in Watts.
If the UPS is 600W then the actual apparent power available is more in VA.
There is something called Power Factor (PF) or vaguely efficiency at play in all UPS and device power supplies too.

VA x PF = W
VA - Rating of UPS
PF - Power factor (number between 0 1nd 1) of efficiency in %
W - load that it can support

Most small UPS PF is between 0.5 and 0.8 (60% - 80% efficiency). Even though they claim > 80%, I would take it with a pinch of salt.

Lets take an example
APC Back-UPS 600 (relevant specs below)
Output power capacity - 360 Watts / 600 VA
Max Configurable Power (Watts) - 360 Watts
Battery Volt-Amp-Hour Capacity - 60
(really don't know how they specify this; as the common measure for battery is Amp-Hour at a nominal Voltage, not Volt-Amp-Hour; assuming it is a 12V battery then its capacity is 5Ah)

This UPS has a PF = 360/600 = 0.6 (60%)
Now for run time (from their own website)
Load Time
50W 40min
100W 25min
200W 6min
300W 2min

As you near the max rating in Watts, the run time decreases drastically.

Now lets take your device (router). It uses a wall-wart for AC/DC conversion. Wall warts can be good or bad. Most are not efficient, meaning a portion input power goes in heat.
At 12V/1.5A it is an 18W hog (gigabit Eth and hi-speed wifi; not exactly a power friendly combo); add wall-wart power loss of 7W. That bring it to 25W load.

On the above UPS example, you may get about 1.5 hours. On a home 850VA UPS with a larger battery (say 150Ah) you can get a much much longer run time. Not because of the UPS rating but beacuse of the battery.

Hope explanation this helps. This is the best I could come up with the available info.

Cheers,
Raghu
Thanks a lot for ur explanation.
My engg. days came back :eek:hyeah:

anyways i m going for this prod

Amazon.in: Buy Resonate RouterUPS CRU12V2 Power Backup for WiFi Router (Black) Online at Low Prices in India | RESONATE Reviews & Ratings

Best for my requirement..it wil give 3-4 hrs backup...
 
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raghupb

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Engg days came back!!
We should write to the University to take back the degree :)

How are you managing in Bengaluru without a home UPS. BESCOM/KPTCL are not very reliable.

Cheers,
Raghu
 
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music4mhell

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Engg days came back!!
We should write to the University to take back the degree :)

How are you managing in Bengaluru without a home UPS. BESCOM/KPTCL are not very reliable.

Cheers,
Raghu

My engg degree is already gone, now i am a Manager in Financial Accounting :eek:hyeah: So officially i am not an engineer anymore after my MBA degree :(

Anyways, i am not worried abt the power cuts, i just ordered one Resonate RouterUPS for my router and 20,000 Mah power bank for my MOJO and mobile.

With one good pair of headphone (HD650), i can spend hours without electricity :D

That's plan, you can suggest me if i can execute it in a better way :rolleyes:
 
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