UPS for computer

I have a computer which functions as my firewall, PieHole, router, etc

I currently have a Cyberpower 1500VA similar to this unit:

Amazon.com: CyberPower CP1500PFCLCD PFC Sinewave UPS System, 1500VA/1000W, 12 Outlets, AVR, Mini Tower: Electronics

their specs are total BS since it uses two 9AH 12.6V gbatteries which give a max of 227watts.

At a reasonable discharge one can cut that in half, so maybe 1Hr at 120W.

I'm thinking of ruining wires to a pair of these:

Amazon.com: Deep Cycle SLA Replacement Battery 12V 35AH AGM Battery- Replaces Husqvarna YTH2448 Lawn Tractor Battery- Chrome Battery: Automotive

Which should reasonably support a 120W load for about 7hrs.

Has anyone done something like this?

My biggest concern is the inrush current charging the batteries after full discharge.
 

ubergeeknz

Member
2018-08-31 12:32 pm
Should be ok, but keep in mind small UPS are only designed to run at full tilt for around 2-3 minutes, tops. They hit the batteries really hard too in this situation, as you have duly noted.

However at less than 10 percent load, it should be happy enough running for hours and hours.

Charging current won't be an issue. Lead acid chargers are CC/CV anyway, so it will be current limited. It may take a long time to charge them up (again, it may get hot doing this as it's engineered to charge a smaller capacity only).
 

PRR

Member
Paid Member
2003-06-12 7:04 pm
Maine USA
www.diyaudio.com
If the power is out, you probably do not need the firewall until the power (and other devices) comes back on.

You run a wire between. The UPS yells "I'm going to die soon!", the PC does a quick but proper shut-down, with a "Go ahead and die now!" at the end.

two 9AH 12.6V gbatteries which give a max of 227watts.

Properly, 227 Watt-Hours. Use your units.

Unless this is an industrial piehole, consumption may be nearer 60 Watts, so several hours. I have run PCs that way. However the normal practice IS to use the wires and drivers to request a safe shutdown, and then power-off.
 
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Sangram

Moderator
Paid Member
2002-09-25 11:01 am
India
UPS are only meant for backup (safe shutdown) and not operation of connected equipment.

To run extended periods you need sine wave power systems with batteries - either inverters or 'online' UPS systems. The WH rating on the batteries determines runtime and the rating on the UPS determines max permissible load. You size the UPS as per the load, and the batteries as W x H X load.

I have a 350W (600VA) UPS with two SBCs for Pihole, a wireless router and a few external hard disks. 40W, tops. You'd think it would allow an hour of runtime, but it gasps at the 10-minute mark. Luckily these aren't devices that need safe shutdown.
 

mchambin

Member
2011-03-13 8:21 pm
UPS are only meant for backup (safe shutdown) and not operation of connected équipement
Yes because of the limited time available from the battery capacity.
However
A car battery wired to a 12V ups works like wonder. Then you can run your car with battery jumpers to the UPS battery for extended mains power outage.
This set up gives you a free mains power generator.
Beware of exhaust fumes that are deadly in a closed garage.
 
Yes 227 W-H

If you read the linked UPS you will see that it is a sine wave output UPS. It is rated at 1500VA(R)/900W (probably good for half that). With that type of rating it could have undersized heat sinks for full load considering up time will be very short. At reduced load of less than 100W it should be good.

The system has a USB interface between the system and UPS.

The issue is that (1) the hold up time is relatively short, measured around 30 minutes, (2) I'm not home during the day, and (3) It is running LINUX and it is a PIA to reboot the hypervisor and all of the VMs running under it.

In addition, there are times when power is out and I don't want to drag the aux generator out of the shed and connect it if I think power will be restored in a few hours.

It would be nice to have wireless devices still operate on the network since my laptop, tablet and cellphones are good for more than four hours.
 

kevinkr

Administrator
Paid Member
I use a 650VA APC BACK UPS to power my modem, router and cloud server, run time is about 2 hours which has always been more than enough to keep my internet and wifi network up during a power outage.

So this should be achievable as long as the load is light, I can understand the concern.

Hope it works, if it doesn't there are likely surplus server class UPS with long hold up times that you can acquire and clean up.
 
I work repairing them. Usually they have a reliable bat charger, so it is not a problem to increase the bat capacity, at the expense of larger time also to charge them.

Also they are temperature control of the unit (one or more NTC/PTC and or bimetallic devices), some give an alarm/warning, olders simply shut down when temp is dangerous. So, use them and no worry about it.
 

mchambin

Member
2011-03-13 8:21 pm
Indeed, a UPS is an excellent battery charger.
There is no limit to the battery capacity, it just takes more time to charge a flat battery.
The UPS is perfect to keep it fully charged, and shield your computers from main power surges.
About running for long periods from battery power only, standard car batteries don' t like it. A couple of near flat condition ruins them. Most claimed deep discharge car starting batteries is commercial BS. The real deep discharge lead battery as used in traction vehicules and camping cars is much more expensive, using no compromise much thicker lead plates.
 

JWNash

Member
2020-02-21 9:29 am
London
Should be ok, but keep in mind small UPS are only designed to run at full tilt for around 2-3 minutes, tops. They hit the batteries really hard too in this situation, as you have duly noted.

However at less than 10 percent load, it should be happy enough running for hours and hours.

Charging current won't be an issue. Lead acid chargers are CC/CV anyway, so it will be current limited. It may take a long time to charge them up (again, it may get hot doing this as it's engineered to charge a smaller capacity only). If interested, read here, Nickname Writer Essays. It is painted in great detail, there is a lot of other information painted.
 
I have the exact same CyberPower UPS. It is a bit over 1 year old and has been run to low battery shutoff several times. It powers this AV workstation which consumes 250 VA before even starting the PC. The power consumption is 340 to 550 VA depending on what the PC is doing.

The display on the left is a cheap 40 inch Walmart 1080 TV which has no mention of power consumption on it. The display on the right is a bottom of the line Samsung 4K which states "typical" power consumption 45 watts.

There is a cabinet full of music synthesizer stuff, and a few more pieces in the rack above the PC (the blue dot in the lower left).

I started up FL studio and had it playing a 15 track recording through the monitors using the left TV screen. I streamed a 4K video from YouTube and put it on the right TV screen. Power consumption was 350 to 370 VA. Run time was 16 minutes before everything abruptly went dark.

If there is a power hit while I'm working I will shut down all but the PC stuff and the left TV. Run time in this case is from 20 minutes to 1 hour depending on how long I give it before starting the shutdown. We get quite a few short outages where the power company retries several times until it gives up, or blows the breaker on the shorted line. In this case it's a 5 minute blackout with several low voltage retries. Otherwise it's dark and cold for several hours or more....generator time.

long periods from battery power only, standard car batteries don' t like it. A couple of near flat condition ruins them.

I got a giant trolling motor battery from Walmart in 2012. It's still going strong, but I have not tested it's capacity recently. It's rated for 114 AH...at 1A. I use a 20 year old 700 VA ugly wave inverter to run stuff at outdoor events. It would run a load of 300 to 500 watts for a couple hours before I start the generator up and ram feed it 33 amps until the voltage reaches 14.4 volts. I let it drop to about 11 volts before restarting the generator.
 

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