MAh, UPS power consumption of laptop

[jackson6612]

I'm not a physics or science student. So, please explain in as much detail as possible. Thanks.

Suppose the total power consumption of my laptop plus router is 100W or 100J/s. The UPS is rated at 200mAh and the standard voltage is 220V. The rating of the UPS would mean that it can deliver current of 200mA for one-hour at voltage of 220V which equals (0.2A x 220; power = IV) 44W or 44J/s. Does this mean the UPS won't be able to run the system comprising a laptop and a router because it needs 100W?

Please help me. Thanks.

 

[russ_watters]

No, it will just power it for less than one hour.

 

[berkeman]

I'm not a physics or science student. So, please explain in as much detail as possible. Thanks.

Suppose the total power consumption of my laptop plus router is 100W or 100J/s. The UPS is rated at 200mAh and the standard voltage is 220V. The rating of the UPS would mean that it can deliver current of 200mA for one-hour at voltage of 220V which equals (0.2A x 220; power = IV) 44W or 44J/s. Does this mean the UPS won't be able to run the system comprising a laptop and a router because it needs 100W?

Please help me. Thanks.

So the UPS is rated to have approximately 220mA * 220V = 44Whr of energy. As Russ says, less than an hour of operation for a 100W load...

 

[rcgldr]

There should be a maximum wattage rating for the UPS as well as it's capacity versus load.

I have a UPS with a rated max load of 900 watts for about 3 minutes, and it can run 430 watts for about 7 minutes, and 280 watts for about 15 minutes. So about 45 watt hours to 70 watt hours depending on the load. It has an "apparent power" rating of 1500 volt amps, so a power factor of .6, since it's real power is 900 watts.

 

[jackson6612]

Thank you, Russ, Berke, and RCG.

So, that means I should also look for maximum wattage, maximum energy per second, the UPS could deliver?

So the UPS is rated to have approximately 220mA * 220V = 44Whr of energy.

I have a UPS with a rated max load of 900 watts for about 3 minutes, and it can run 430 watts for about 7 minutes, and 280 watts for about 15 minutes. So about 45 watt hours to 70 watt hours depending on the load. It has an "apparent power" rating of 1500 volt amps, so a power factor of .6, since it's real power is 900 watts.

From the above discussion it seems to me 1W = 1 volt amp = 1Whr?

I don't under the red parts. Does 45 watt hours mean the power of 45 watts for one hour?

How do you get that power factor of 0.6?

Perhaps, the answers to these may seem obvious to you but they are not for me, so please excuse me. Thanks.

Best wishes
Jackson

 

[rcgldr]

So, that means I should also look for maximum wattage, maximum energy per second, the UPS could deliver?

Yes, that should be included in the UPS specifications.

From the above discussion it seems to me 1W = 1 volt amp

Yes, a watt is a unit of power and equals 1 volt amp (or 1 Newton meter / second):

http://en.wikipedia.org/wiki/Watt

1 W hr

That is a unit of energy. 1 watt hour = 3600 Joules.

http://en.wikipedia.org/wiki/Kilowatt_hour

http://en.wikipedia.org/wiki/Joule

Does 45 watt hours mean the power of 45 watts for one hour?

Yes, at maximum load, the UPS I use can generate 45 watt hours or 45 x 3600 Joules of energy. Normally maximum load occurs at a much higher wattage at a much shorter duration, in the case of my UPS, that 900 watts for 3 minutes. This is partially due to how the batteries work. The higher the load, the smaller the energy capacity of a battery.

How do you get that power factor of 0.6?

It's related to AC power and phase of current versus voltage:
power_factor = real_power / apparent_power
apparent_power x power_factor = real_power
apparent_power = real_power / power_factor.

http://en.wikipedia.org/wiki/Apparent_power#Power_factor

I'm not sure apparent power ratings are too important in a UPS, what you want to know are the maximum real power, and the duration at that power, as well as the duration at lower powers.

 

[russ_watters]

From the above discussion it seems to me 1W = 1 volt amp = 1Whr?

No, 1 Watt is 1 volt-amp is 1 joule per second. These are rates. Power outputs, not energys. 1 watt for 1 hour is 1 watt-hour. 1 watt for 1/2 hour is 1/2 watt-hour.

I don't under the red parts. Does 45 watt hours mean the power of 45 watts for one hour?

45 watts is 45 watts regardless of how long it is applied.

How do you get that power factor of 0.6?

Power factor is a whole 'nother complication. A volt times an amp doesn't necessarily give you a watt in A/C if the phases of the volt and amp are misaligned (gives you less). .6 is probably too low, but it might be .8 for a computer.

 

[jackson6612]

Thanks a lot, RCG, Russ. You have really helped me.

In next couple of my days I'm going buy a UPS. I need maximum 100W to run my computer system. I'm not very good with this kind of stuff. What particular specifications I should be looking for - you know there are too many there? I should look for mAh, maximum wattage, and ...?

It would be a dry battery UPS delivering about 220V.

Please guide me.

 

[rcgldr]

The UPS specs tend to exaggerate. If you're computer uses 100 watts, you probably want a UPS that can handle at least double that, or 200 watts max. How long it can run at that load will depend on the capacity of the UPS (mostly the batteries it uses and efficiency).

dry batteries

That's unusual. Most of the UPS systems I've seen use sealed lead acid batteries.

 

[jackson6612]

Thanks.

How long it can run at that load will depend on the capacity of the UPS (mostly the batteries it uses and efficiency).

The capacity is related to mAh, right? The efficiency etc. is all about good brand and how much I'm ready to invest, right?

That's unusual. Most of the UPS systems I've seen use sealed lead acid batteries.

I don't know. Doesn't acid drip out of the batteries? By a dry battery they mean the one which uses the material in paste form. Using 'dry' batteries offers portability in moving from one place to another without the danger of acid leakage.

Thanks for all the help.