I need to fixup a 1500VA USP to run longer. This is a pseudo sine wave unit. First I plan to derate it by 50% so I will draw no more that ~700VA. Remove the existing internal batteries and set aside. Then I plan to hook up two 12V marine deep discharge batteries in series to provide 24VDC using appropriate wire gauge.
So far maybe so good? Suggestions please.
Using CyberPower rather than APC since I am hearing that APC eats batteries before their time with too much testing.
On Mon, 18 Jan 2016 16:48:39 -0800, AncientOfyears put together some random words that came up with:
Did the same thing using a APC SmartUPS. Used the biggest marine batteries I could find. Used it to power a phone system and alarm system. The thing supplied power for around 4 days before the batteries went dead.
How long? If more than a few hours, I suggest a Honda inverter generator.
On the bottom of my APC BE550G UPS is the following inscription: The output of this device is not sinusoidal. It has a total harmonic distortion of 45% and a maximum single harmonic of 35%. Assuming APC is talking about voltage distortion, a THD of 45% means that 0.45^2 = 0.20 = 20% of the total output power is wasted in harmonics of 60 Hz. If you're driving a motor, transformer, or have a switcher with a low pass input filter, or running a device that really hates harmonics, you're going to have problem. Resistive loads are ok. Switching power supplies are usually ok. Choose your loads wisely.[1]
Duz your proposed and unspecified model CyberPower UPS have a fan? You'll probably need it. UPS's are also rated for some number of hours of operation or some percentage of duty cycle. I suggest you check the specifications.
They're called "deep cycle". The problem is that the original batteries are probably AGM (Absorbent Glass Mat) batteries, which are charged to some specified maximum voltage at a given temperature. If you replace these with a different chemistry battery, such as lead-acid flooded cells commonly found in automotive and marine batteries, the charging characteristics and maximum charge voltage will be different. I'm too lazy to dig out a table for you, but I think you'll find that they're different. Also, removing the batteries from the case also removes them from being thermally connected to whatever temperature sensor is built into the UPS. Fortunately, you can extend the leads on those and attach them to the battery box. That's the sensor on the right:
To make matters worse, the various UPS manufacturers compete with each other for the longest runtimes. To achieve high numbers, they charge the batteries with an EOC (end of charge) voltage to be as close to maximum as possible. This is not good for the life of the battery, especially when changing battery chemistry. They also charge as quickly as possible, which is yet another reason for relatively short (5-8 year) battery life in a UPS. Fortunately, when going from the stock battery, to a much larger battery, the lower relative charge rate will help extend the battery life.
Among consumer UPS's, APC is about the best I've seen. The others, including CyberPower, are worse. However, comparing the pseudo sine wave APC products (BackUPS) with the sine wave products (SmartUPS), the SmartUPS products are much better. Among the various UPS's I own and those I manage, 5 years battery life is about the average. If I reduce the charge profile to charge slower, and terminate the EOC at less than 100%, it won't run as long or recover as quickly, but the batteries will last much longer.
I recently scribbled this rant about repairing APC BackUPS XS1300/1500 UPS's. Might be of some interest:
[1] One of the fun tests are running two UPS's in series. With a pseudo sine wave, the 2nd UPS will often complain that the power from the first UPS is too dirty to be useable.-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
NOT a good idea if it originally used 12V!! I got a USED APC 330 XT+ (maybe 2-5 yrs old then) and it has been providing excellent service for about 25 years; replaced battery about 4 years ago.
I did this years ago using an APC SmartUPS 1000 and two used sealed lead batteries the size of a car battery (don't remember the capacity, was like
60Ah or so).It did not work well. The charge current output by the APC (designed for the standard 17Ah batteries) was not correct for those big batteries, and they quite quickly became very unbalanced (one fully charged the other one still mostly empty) and the UPS became confused.
I don't know if it was caused by the batteries already going dead (they had been in a large PBX for some years) or by the mismatch between the UPS designed capacity and the actual capacity. Maybe both were a factor.
Anyway, whatever you do make sure the connections are safe. The voltage of the batteries is safe but the short-circuit current isn't!
Sorry, but I disagree with that statement. The voltage distortion is just that, and how much of those higher harmonics are converted into heat is totally up to the load's characteristics.
Loads with an inductive component (i.e.: R + jX) tend to have a much higher impedance for the higher harmonics than for the base harmonic (60 Hz), hence the power lost in the higher harmonics is lower than the percentage of voltage distortion for that harmonic. An additional factor that limits the Watt-losses (real power, or active power) is the fact that higher harmonic currents have a bigger lag.
Yes. In a motor it can give torque pulsations and additional heating (not proportional with the voltage harmonic distortion), but enough to overheat the motor if it's operated at its rated power. It has been a problem with PWM-driven motors in the past (apart from the high dV/dt-s that are associated with switching converters, leading to partial discharge in the insulation and eventually to failure).
In a transformer it will potentially generate all kinds of sounds and can lead to the same overheating problem as in the motor.
In that case the switcher has solved the problem for you: the higher harmonic voltages will not lead to (significant) higher harmonic currents.
Yes, negative emotions like hate mostly lead to problems. :)
Yet those are the one to which your statement applies most.
Although their input capacitor can get severely stressed by the higher harmonic voltages, leading to higher currents than the design may have anticipated.
That's funny. :)
joe
}snipped probably the most informative part{
Series? Did you mean parallel?
No way would it work with a higher voltage. Even in parallel the charger might not like putting out more current.
And if you get a loose contact it might arc and not stop, unlike AC where an arc extinguishes itself during a zero-crossing of the current, leading to fire and no fuse blown.
joe
The harmonics can also be reflected back to the UPS. In extreme cases, the harmonics can also be radiated. As I previously mumbled, the ability of the load to use the harmonic power is dependent on what manner of load it presents to the UPS. A purely resistive load can use it all. Something with a 60 Hz low pass filter on the input will have problems.
Those same inductive loads often have filter and bypass capacitors across the line, which lowers the input impedance at higher frequencies and are useful for passing FCC Part 15 conducted emissions tests.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Yes, harmonic currents can do some bad things when encountered by a power line filter.
Yes, that's a useful addition.
Maybe you should consider writing your mumblings down, because from here I can only read what you write, not hear what you mumble. :) But IF I read you mumbling, then it was that 20% would be wasted in harmonics (of 60 Hz--in Europe that would be 50 Hz, I guess). You didn't write it as depending on the type of load. In what follows you only wrote about the possibility of problems, depending on the load.
joe
No, those popular "shoebox size" APC and other makes UPS do have two
12v batteries in series to get 24v to operate the UPS.Larger ones have even more batteries in series. Running at a higher DC voltage makes it easier to get an efficient inverter to AC.
So what I am getting out of this is
Mod a UPS that uses only one battery i.e. 12V Get a higher capacity SLA.
These UPSs I already have so I would not need to buy a larger USP.
May need several UPS to get the VA I need.
This is for an unattended security system.
I really need to do a cost benefit analysis on this.
(snip)
From the personal safety viewpoint, DO check that the battery system is at or close to earth - ground to you furriners - and/or UPS output neutral potential. What you *may* discover is that a lot of UPS inverters have the batteries at half-AC-output voltage. Whether you are at ease with that is something you should consider.
Make sure the UPS has proper fan cooling for extended run.
I tried just this years ago and the UPS overheated and then exploded (all the power transistors blew up). It was never designed for extended use off larger external batteries. Whoops.
I can personally attest that APC UPS' suck so bad they suck at sucking.. They overcharge and end life early for the batteries installed into them.
They also fritz out and act like there isn't even a battery installed and recover after a power line cycling, which is beyond lame if one's intent is to keep what is plugged into it up and running.
I got a used APC 330 XT Plus; ran without any problems for 5-6 years, handling brownouts and blackouts like a champ. Then had to change the battery as it was finally dying. The new battery is still going like a champ after about 5 years. Equipment must fall apart around you, because (other than you) i have heard only good stories about the APC brand (if not abused).
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