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Uninterruptible power supplies

I was watching an item on TV about use of batteries to balance the national grid. I have also heard it said that the supply is likely to become less reliable with increased dependence on renewables.

I have always assumed that an uninterruptible power supply must be energy inefficient for the same reasons as stand-by uses electricity. Is this a correct assumption or does a UPS not consume any electricity at all unless it is brought into use?

As an aside, could a power cut ever damage a modern computer (say if you happened to be installing an update or defragmenting a disc when it happened)?

Reply to
Scott
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a UPS generally does consume a background amount of power, how else do they cook their batteries with heat? The amount will vary depending whether it's an offline, online, or line interactive type.

Reply to
Andy Burns

Thank you. This is what I suspected. Could you quantify at all? Would a domestic UPS use more power than, say, a TV on stand-by?

Reply to
Scott

Yes, but only journalists who can't do sums, and battery manufacturers, see a major role for batteries in solving this problem.

It always consumes some, for the electronics and for charging the battery. And the best kind, with an inverter always online, lose power in the inverter.

Yes. Depending on the filesystem and luck it could damage it even if it is not actively doing anything.

Reply to
Roger Hayter

The battery charger is not 100% efficient. Once fully charged the battery is often then overcharged continually. Turning 12v or 24v back to 110/230v is also not entirely efficient.

For sure, your filesystem can be totally borked - though it usually survives unharmed. NTFS has been much hyped as more robust in this respect, but it's only a limited subset of data that gets duplicated, so it's almost as vulnerable as FAT32.

Roger summed it up very well with "Yes, but only journalists who can't do sums, and battery manufacturers, see a major role for batteries in solving this problem."

Even if UPSes were 100% efficient, they would still not be practical for grid backup. The costs, pollution, energy consumption in manufacture and vast demand for lead would be problematic.

NT

Reply to
tabbypurr

Batteries have internal resistance. Which varies according to type of battery, age and state of charge. Ergo Ohms law applies. W=I2R Both charging and discharging.

Reply to
harry

Don't fret. Buy yourself a laptop.

Reply to
harry

formatting link
wonder how much that will cost.....?

Reply to
Jim GM4DHJ ...

Yes but so could a hardware fault or a software crash. This is why you need a good data backup system. It will allow you to recover from a corrupted disk caused by anything.

Also UPS systems fail too.

Reply to
dennis

That'll be why 450 MW (ish) of battery was called upon to help keep the grid up the other Friday. Mind you it's not been stated for how long said "battery" could supply that power...

More likely to be lithium than lead. But isn't there some other weird and wonderful battery technology about using molten sulphur or something?

Reply to
Dave Liquorice

My APC Smart UPS 700 doesn't any more. The Friday cut and the much longer one the follwoing Mondy proved that the mods I have made to it have stopped it killing its batteries.

It used to kill a set of batteries in around 4 years. After the last lot almost went into literal meltdown (the smell is what alerted me) I made some mods before putting a new set of batteries in. That was March 2014, so without mods they would be dead or next to useless by now.

The UPS kept everything it's supposed to up for the 20 odd minutes of the Friday outage. On the Monday it ran for the expected time before shuting down with low battery. The recharge time before switching back on was as expected as well.

The mods where reducing the charge voltage, and fitting a temperature controlled fan and possibly some tweaks to firmware settings. A search back in here may well find more details.

At a rough guess I'd say mine takes 15 W +/- 5 W.

Reply to
Dave Liquorice

in the mid 1990s I was working in a building which sat astride the Great Weatern Railway and was a terminus for one of the London Underground lines. One weekend, We were warned that there would be work on our electrical supply so all computer equipment should be turned off. OUr IT people said "don't worry about that we have UPS". On the Monday morning it was found that every UPS had blown up because of over voltage. It was well after 2pm that my computer came back to life.

Reply to
charles

I did a minor adjustment with the "hidden" serial command, can't remember the exact float voltage I set 27.something, whatever the Yuasa spec said, even though they're not Yuasa batteries in it.

Mine has 4 of the 18Ah batteries and now the electronics lump at the top of the case still gets warm (it's often running in buck mode) noticeably above ambient, but the battery lump at the bottom of the case is nowhere near as warm.

Mine were last changed july 2015, I no longer do the weekly test, but they worked last time I checked.

Only seen that when someone had fitted "alarm" batteries, rather than "NP" batteries.

I think mine was about 30W for a SU2200 plus the same again for an 8 way smart PDU, but then I realised I didn't exactly need to remotely power-cycle individual kit, so I no longer use that.

Reply to
Andy Burns

54.05 volts.
Reply to
Andy Burns

Decent servers have two power supplies.

Wise IT people connect one to the raw mains, and the other to the UPS, so if either fails it keeps going.

Andy

Reply to
Vir Campestris

Half a gigawatt is a long way from running the grid

NT

Reply to
tabbypurr

Depends on the type of UPS. The best of them charge the batteries all the time and use the batteries to power what it is powering, so all that happens on a mains failure is the batteries stop being charged. Those clearly do waste some power all the time. The other sort that switch over on a mains failure only waste power when replacing the self discharge.

Not when defragging. It can happen when flashing the bios.

With updates, it depends on whether you have a full backup etc.

Reply to
jeikppkywk

Yes sudden power cuts do screw up computers. It really depends what is going on at the time. Many now use laptops for this reason of course, it has its own built in ups.

Brian

Reply to
Brian Gaff

Hardware mod on mine. If there was a firmware tweak it either didn't do what it said it would or had undesirable knock on effects. I have vague memories of the latter.

Once I have a bit a spare cash I might get a set of batteries for the SU2200 I have sitting doing nothing...

It was getting the UPS that alerted me to the fact our supply voltage was high. Plugged it it, straight into voltage reduction mode, measure supply close to 250 V, rang DNO, engineer at door inside two hours, they measured agreed it was high, came back within a couple of days and andjusted the tapping on "our" pole transfomer. Voltage now

240 and, at that time, the consumption of incandescent light bulbs noticably dropped...
Reply to
Dave Liquorice

True but it might be the half a gigawatt of dispatchable that keeps the frequency up just enough...

Reply to
Dave Liquorice

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