How much power an UPS requires to run itself ?

[Anonymous user]

Hi All,

I have a APC SU 700 INET UPS, 750VA/450W. It is customized to work with 24V. I think so because I haven't found this model to be a 24V yet and it doesn't run with one 12V battery. I am using it with 2 x 12V/45 AMP batteries (connected serially to produce 24V). Place where I live, you might find it interesting, in the meaning, there is almost 12 hours power outage every single day. So, I know the UPS itself in no way would be able to charge those batteries in the given hours of electricity. So, I've hooked 2x12V/40w Solar Panels (serially to produce 24V)  to have those batteries charged. The New batteries are one year old and worked very well during the first year. Now, it has become frequent that I get low battery indicator On, and the battery voltage drops down to 11.90, and I have to shut down the UPS. I have several questions in my mind :

1. Are those batteries not getting enough charge that it could support load ? The load is not much, during day it is pretty much just one laptop whose adapter reads Output 18.5W 3.5 Amp, other than that 2x 20W CFL bulbs use the power for about 5 hrs at the most during evening.
2. At what rate my UPS charges the batteries, in Amp/hr while there is electricity ?
3. The solar panel I use reads [Max Power : 40w ; Operating Voltage : 17.2 V ; Operating Current : 2.32 A ; Open Circuit Voltage : 2.16 V ; Short Circuit Current 2.57 A]. During day, when sun is bright it reads around 27VDC at the charge controller, tested with digital multi-meter, during this time at what rate it charges the battery (in Amp/hr) ?

And important of all

How much power (Amp/hr) my UPS requires just to run itself (without any load) while running in batteries ?

Thank you for your time and support.

[Anonymous user]

Hi All,

I have a APC SU 700 INET UPS, 750VA/450W. It is customized to work with 24V. I think so because I haven't found this model to be a 24V yet and it doesn't run with one 12V battery. I am using it with 2 x 12V/45 AMP batteries (connected serially to produce 24V). Place where I live, you might find it interesting, in the meaning, there is almost 12 hours power outage every single day. So, I know the UPS itself in no way would be able to charge those batteries in the given hours of electricity. So, I've hooked 2x12V/40w Solar Panels (serially to produce 24V)  to have those batteries charged. The New batteries are one year old and worked very well during the first year. Now, it has become frequent that I get low battery indicator On, and the battery voltage drops down to 11.90, and I have to shut down the UPS. I have several questions in my mind :

1. Are those batteries not getting enough charge that it could support load ? The load is not much, during day it is pretty much just one laptop whose adapter reads Output 18.5W 3.5 Amp, other than that 2x 20W CFL bulbs use the power for about 5 hrs at the most during evening.
2. At what rate my UPS charges the batteries, in Amp/hr while there is electricity ?
3. The solar panel I use reads [Max Power : 40w ; Operating Voltage : 17.2 V ; Operating Current : 2.32 A ; Open Circuit Voltage : 2.16 V ; Short Circuit Current 2.57 A]. During day, when sun is bright it reads around 27VDC at the charge controller, tested with digital multi-meter, during this time at what rate it charges the battery (in Amp/hr) ?

And important of all

How much power (Amp/hr) my UPS requires just to run itself (without any load) while running in batteries ?

Thank you for your time and support.

[BillP · Accepted solution]

This UPS is very old and discontinued so what I can contribute is for the load losses (at zero load) to give you an idea of what the power consumption of the UPS all by itself is. I think this will also assume a fully charged battery.

Bellow is the tool for the UPS Efficiency Comparison Calculator. I would suggest looking at the most similar model to this UPS to get an idea. Newer UPSs are a little bit more efficient but this will give you an idea that is close to what your UPS utilizes. SUA750I is the replacement for SU700INET so I'd suggest using that and comparing it against itself and dragging the load percentage to 0%.

http://www.apc.com/tool/?tt=5

I see the answer for this UPS at 17W and it will be a little more if it is charging the batteries as well but it sounds like you're not using the charger)