Smart-UPS XL 1000 + APC UXBP24 - Battery backup time Inconsistency

[Anonymous user]

Hi,

I am using the above mentioned devices as backup power for 4 PCs (4 CPUs + 4 Monitors). I am having a problem which I am not able to understand why, so can some one please give me a solution or an explanation.

Whenever I do a calibration testing through the APC Business chute client to check the backup time for the UPS with the battery pack I get a battery time of little over 7 hours, I know the UPS is drawing power from the battery during this test, because the UPS indicated that it running on battery and the UPS fan is on.

But when I pull the power cord for the APC from the AC supply and make it run on the battery the backup time is little less than 3 hours.

Can some one give me an explanation or how I could get a consistent result.

Thanks

[Anonymous user]

Yes the battery count is set for 5. These units are brand new, 4 months old. The UPS is the APC SMART-UPS 1000XL with the UXBP24 battery pack.

[TheNotoriousKMP_apc]

Suhan,

I'll assume you're currently using USB since you're asking if there's a difference. If you can do the following with some downtime, we can test for sure:

1. Power off all attached load
2. Power off UPS and disconnect from the wall.
3. Disconnect the communication cable
4. Depress the Off button for 4-6 seconds until you hear a click and the front LED's flash.
5. Hook the serial cable up and re-attach the load and power everything up.

Now, open up Hyperterminal (2400/8/n/1 No Flow Control)
Press Shift+Y (should return "SM")
Press Shift+(Period) (Should return "005")
If it does not, let me know.

Also at this point you may want to reinstall the Agent because you're on Serial communication.

[Anonymous user]

Hi,

I will not be able to test this out, because the computers that are connected be taken down right now. I will have to perform this test some time tomorrow morning or later on Friday.

[TheNotoriousKMP_apc]

In the PCBE interface for the device, do you have "005" for the Battery Pack Count? When was the last time the internal batteries were replaced? What's the full model number of the UPS that you are using? It's possible you'll need to contact Tech Support and request a calibration key be sent to you if it is an older model.

[TheNotoriousKMP_apc]

Hi,

When you do the pull plug, do you have anything that's setup with PCBE to perform a shutdown at all? Shutting down after 50% of battery life, when you initially have a "7-hour" runtime and your equipment/UPS is powering off after half that time, there's either a large shutdown schedule, or an extremely non-linear load that's increasing as the UPS operates on battery. What exactly is connected to the UPS? If it's a Server/PC, does it contain a Power Factor Corrected Power Supply?

[Anonymous user]

"do you have anything that's setup with PCBE to perform a shutdown at all?" I am not clear as to what do you mean anything setup in PCBE, could you elaborate this please ?

I don't think I have any kind of shut down scheduled in the PCBE.

After the calibration test I let the UPS power back to full before I do the pull plug option. I only have 4 Desktop CPUs (no servers) and 4 17" LCD monitors connected to the UPS. I am not sure if the power supplies are PFC power supplies, but these machines are fairly new, so I am assuming they are.

[TheNotoriousKMP_apc]

In regards to what you asked for clarification on - it's not important. If you had something setup for a shutdown on battery after X minutes, you would've known right away.

Anyways...4PC's and 4 Monitors...on a UPS that's only capable of a maximum of 800Watts. What is your load percentage during normal operation? It has to be EXTREMELY close to 800W, or at least within 100W of an overload.

If they are power factor corrected power supplies and you're SOMEHOW avoiding an overload condition on battery, your runtime is extremely skewed based on the PFC PSU's.

What's happening is that during the transfer time from online to on battery there are capacitors in the PFC PSU that immediately drain to keep the system up and running for that 2-4 Millisecond time. Once the UPS is on battery, the capacitors decide they want to do a full recharge immediately, which increases the power draw on the UPS substantially (here's where it SHOULD be overloading), and decreasing your runtime substantially.

When you do the pull plug, do you watch the software and actually see the runtime decreasing, then @ 3 hours it just turns off?

[Anonymous user]

The load percentage at normal operation with all 4 computers connected is at 2 LED Bars. Also do keep in mind I have the extra battery pack connected as well.

When I pull the plug, the LED bars keep dropping at regular interval and once it comes to the end all the devices just shut off. I also check on the software which shows what the percentage is as it is dropping.

According to you, is there a way I can prevent the overloading phase. So why am I not affected by the overloading problem when I am doing the calibration. Shouldn't this happen during then as well ?

[TheNotoriousKMP_apc]

Keep in mind that an extra battery does not increase load capacity, only runtime.

Do you have the specifications on the Power Supplies for the PC's? Based on the information the UPS is reporting to you, it's providing around 44% load power with 8 devices attached to it, 4 of which are PC's, meaning that it's 44% of 800VA, or roughly 365VA. Still doesn't seem like the UPS is correctly sensing the load.

[Anonymous user]

Hey,

The 4 PC's have a 350 W power supply each.

Another question, when I am setting the battery pack value on the BCE, does it matter if I use a USB cable or Serial Cable. Also does setting the battery pack value on the software client make the UPS recognize the extra battery pack, if so how can I make sure ?

Thanks

[Anonymous user]

Hi,

I will not be able to do this test for another week or so, so let me ask you, what I could do if I do not get "SM" and "5", during this test ?

How can I go about making the UPS recognize the battery pack ?

Thank You

[TheNotoriousKMP_apc · Accepted solution]

If you don't even get "SM" then there's either something wrong with the serial port, or the procedure was done incorrectly.

By already communicating with PCBE you've verified that it can communicate using the Comm board on the UPS, just right now, by USB.