Mecer 800VA UPS

[analogsa]

Got this last week and tried testing it on my bare bones dual core PC. Managed to power it up for about 4 minutes. As desktops have too many hardware variables and i was lazy to sit down and measure actual consumption i thought of trying it on an old laptop. It has a specified max consumption of 70W. Including inefficiency/power correction in the laptop brick worst case scenario is still under 100VA. It worked for just over 10 minutes on UPS power.

Thinking this seemed wrong i took it back to Mustek and today received a call from their tech. He claims there is nothing wrong with it and "they are all like that".

Thoughts?

 

[proximiti99]

Depending on the type of system you're running, (check my sig) the up times may vary. I get +/- 7 minutes from my 1000 vA UPS, also Mecer

 

[analogsa]

My PC is quite different. Gigabyte GA-G33M-DS2R IG33, onboard video, 2GB, 1TB Seagate, Antec 380W, 19" Gigabyte LCD. And anyway, what about the laptop that can't run for more than 10 min?

 

[bekdik]

My server, workstation, switches, adsl, analogue modem etc run for over 90 mins on my 750VA APC ...

It's all dependent on the batteries together with power used, not on the power output capability of the UPS.

You also get what you have paid for.

 

[pierrehugo]

Laptop chargers are not regulated but switching power supplies, they are not made to be efficient but stable. They draw like 0.5A wich is alot of power when compared to a small PC... also VA is a unit of power not enerjy... that has no indication of the capacity of the batteries in the UPS... then again I am not speeking from experience so sorry if I am wrong...

 

[risingtide]

You are quite correct. The VA rating is the maximum output power the unit can deliver, it says nothing about how long it will last. That is dependent on the storage capacity of the battery.

The small UPS's are really only designed to allow you to shut down the computers in an orderly fashion when the power fails, and not to keep you running for an extended period.

 

[analogsa]

You are certainly right gentlemen. The VA rating is largely determined by the size and number of output devices of the inverter and to some extent by the max safe discharge current of the battery. That's why a manufacturer can offer different size VAs using the same battery. I know this. My question is whether 4 min of backup is at all normal for this and similar units. It's harldy enough to save and shutdown. Regarding the inefficiency of laptop chargers even if you allow for 50% efficiency (impossibly low) it still does not seem right. Any owners of the same UPS?

 

[Gnome]

Battery issue aside the VA rating does not determine how much current a UPS can supply continuously! The VA rating is simply the allowable peak power output whereas the watt rating is used to determine how much current can be drawn from the device continuously. You can think of watt as the RMS rating of the device. Therefore a UPS rated at 1000VA CAN NOT supply 1000w of power continuously, it depends on brand but quality UPS's like APC are usually in range of 600W for a 1000VA UPS.

Batteries are of course a entirely different issue, the only way to know is to open the unit and look at the batteries but 5min does seem a bit short, you get what you pay for tho...

 

[proximiti99]

You are certainly right gentlemen. The VA rating is largely determined by the size and number of output devices of the inverter and to some extent by the max safe discharge current of the battery. That's why a manufacturer can offer different size VAs using the same battery. I know this. My question is whether 4 min of backup is at all normal for this and similar units. It's harldy enough to save and shutdown. Regarding the inefficiency of laptop chargers even if you allow for 50% efficiency (impossibly low) it still does not seem right. Any owners of the same UPS?

Umm, Does your PC require more than 4min to save and shutdown, or do you? I've already mentioned, I have the Mecer 1kVa unit and it's crap, so buy an APC or accept what you've bought.

 

[risingtide]

My question is whether 4 min of backup is at all normal for this and similar units. It's harldy enough to save and shutdown.

4 minutes is short. I would expect omething like 10 to 15 minutes at the specified power output. Mustek should be able to provide detailed technical specs.
In my experience, UPS batteries are notorious for giving problems and going bad after as little as one year. Maybe they have improved since I was dealing with hardware a few years back.

 

[risingtide]

These are my calculations based on the specs found on Mustek's website:

Unit:
ME-1000TBK (1000VA): 700W
Battery Type: 12V/7 2 Ah
Number of Batteries:
ME-1000TBK: 3 batteries
Efficiency ~80%

3 (parallel) * 7.2Ah = 21 Ah @ 12V = 252 Wh(Watt hours)

factoring in efficiency and the fact that the battery probably cannot be run down to zero I estimate that 150Wh are available.

Your dekstop may draw something like 400W, computer and monitor. This would give an up-time on battery power of approx. 20 minutes.

That is in the order of what I would expect of a UPS.

 

[proximiti99]

These are my calculations based on the specs found on Mustek's website:

Unit:
ME-1000TBK (1000VA): 700W
Battery Type: 12V/7 2 Ah
Number of Batteries:
ME-1000TBK: 3 batteries
Efficiency ~80%

3 (parallel) * 7.2Ah = 21 Ah @ 12V = 252 Wh(Watt hours)

factoring in efficiency and the fact that the battery probably cannot be run down to zero I estimate that 150Wh are available.

Your dekstop may draw something like 400W, computer and monitor. This would give an up-time on battery power of approx. 20 minutes.

That is in the order of what I would expect of a UPS.

Well done, nice calculation there. However, my PC's running a 700w power supply, and being a gaming machine, I push it hard. O'Ced I expect it to use up to 600w at least, which gives me around 6 to 8 minutes. Thats normal.