BE750G: estimated battery runtime with load not living up to expectations?

[Anonymous user]

hello, i have a BE750G 450 Watts / 750 VA UPS:

http://www.apc.com/resource/include/techspec_index.cfm?base_sku=BE750G-CN

while using the powerchute software, it states the following time remaing on the battery under certain loads:

229W load gives 7 min

220W load gives 8 min

157w load gives 11 min

is something wrong? the runtime chart from APC states that at 225W load there should be 12 minutes of battery time but powerchute says i'll only get 8 minutes. where did the other 4 minutes go?

http://www.apc.com/products/runtime_for_extendedruntime.cfm?upsfamily=21


P.S, here's the technical data from powerchute:


Model: Back-UPS ES 750
Serial number:
Firmware revision: 841.I3 .D
USB firmware revision: I3
Result of last manual self-test: Passed
Last manual self-test date: 04/05/2009
Last battery replacement: 11/09/2008
CPU: Intel Pentium
RAM: 2,048 MB
Free disk space: 106,430 MB
Software version: PowerChute Personal Edition 2.0
Operating system: Microsoft Windows XP (5.1.2600)


is the battery too old maybe? i just bought this yesterday. also, it's been charging since 3:30pm yesterday.

[BillP]

have you actually discharged the UPS and checked the actual "on battery" runtime, versus just using the software?

the software should be fairly accurate but it is most accurate while the UPS is operating on battery. the UPS may need to be "calibrated" too if this is the case. i would try discharging the UPS and actually seeing how much runtime you get on battery. again, the runtime while online is an estimate and it may take a discharge of the UPS battery to perform a little calibration to make it more accurate so the UPS realizes how much runtime it really has.

[Anonymous user]

i unplugged the UPS and let the computer stay on battery power. i guess i should have not let the software shut down the the PC right? that didn't calibrate anything that way.


should i cancel the ups software shutdown process? should i let the PC run until the battery dies and time that? is this bad for the computer or UPS battery?

[BillP]

i would plug unplug the USB cable and all critical equipment such as the computer. if you plug in a lamp or something, let the UPS completely discharge till it turns off and then let it charge back up again with no software interaction. as long as we dont do this 10 times a day, it won't harm the UPS battery or the computer (since you shouldn't leave that plugged in so it doesnt shutdown hard).

[Anonymous user]

okay, just to make sure i got this right..


1) so unplug all equipment from the UPS.

2) unplug the USB cable from the UPS.

3) plug in a light bulb on the UPS.

4) unplug the UPS from the wall so it goes on battery power and let it drain via the bulb.

5) after the UPS shuts down due to being drained, plug in the UPS to the wall outlet and let it charge for a day until it has a full charge.

6) connect all equipment back into the UPS and connect the USB cable.

7) let computer start up and the UPS will self calibrate.


is this correct?

for step 5, do i have to let the UPS completely charge before plugging my equipment back into the ups and turning it on?

Message was edited by: daaan

[BillP]

you are exactly right! the only benefit to plugging your computer and equipment in AFTER the UPS is that if the UPS does need to go to battery, you will have the full runtime. if the battery is at 20% charge and is still charging, if the power goes out, you might drop the load if the runtime is too low. know what i mean?

the UPS should calibrate once its been draining completely and charged back up. also take note of the amount of runtime that you check with a stopwatch or something so we can compare it to the runtime chart to see if its accurate.

[Anonymous user]

there's just one problem though, i won't be able to emulate a sustained 225 watt load (half load for UPS unit) so there might not be a point to time the unit until shutdown. for example, even if one 40 watt bulb can last an hour, i don't think it necessarily means that two 40 watt bulbs will last for half hour. sometimes it's not linear like that.

but i will try to drain the UPS as soon as possible to see if it will self calibrate.

[BillP · Accepted solution]

yeah i agree. but lets see how this works out and go from there.