UPS - Uninterruptible power supply - not the courier!

[Skipper Billy]

Anyone know about UPS ??

We get a lot of power cuts here - had one tonight for 10 - 15 mins.

Luckily it hasn't happened whilst I have been imaging but thinking ahead it struck me that a UPS could save a session but I know nothing about them.

Any tech gurus point me in the right direction ?? I run a PC, mount, 2 cameras, dew bands, electronic focuser, etc - about 10 amps max.

[Davey-T]

A few how toos on Y'Tube, if I was building one nowadays I'd be inclined to use a 40ah Tracer LifePo battery.

Dave

[spillage]

ups

This one is okay and cheap. Only has 15-20 min runtime. Should be able to get a discount code as well.

[Lonestar70]

A lot depends on how much run time you require in the event of a power cut.

There is a good  article on how to choose one here: -

https://www.howtogeek.com/161479/how-to-select-a-battery-backup-for-your-computer/

The best types are the on-line type, since they totally isolate your equipment from the mains at all times.

Hope this helps.

 

[symmetal]

As most of your equipment is 12V you could run everything of a leisure battery with the battery permanently on charge using a Ctek charger or similar which won't overcharge the battery. If you have a desktop PC get a 240V inverter to run it off the battery all the time. It needn't be a large capacity battery if it's only needed for 20mins or so, but a 100AH battery you can still use it if your power is off all night. If it's a laptop then you won't need an inverter for a short outage.

Alan

Edited November 3, 2017 by symmetal

[Dr_Ju_ju]

As others have stated, if you want to ensure that there is no interuption to the power feed to your devices, then go for a low voltage (battery) system that permamnently runs all your equipment, but is on permanent Mains charge.

The reason I say this, is that for many UPS devices, while they will detect the loss of mains power and auto switch over to a battery\DC inverter, there will be a time lag. The lag may only be a few ms, but this 'glitch' can have issues with some down-stream devices tripping out, USB's failing etc.

[Skipper Billy]

Thanks guys - very helpful as always.

[Stroller]

Hi David,

I know you have said "about 10 Amps" and I know from our previous discussions roughly how your kit and Obsy are laid out but to get the best 'bang for your buck' it is best to 'size' the UPS based on the exact power usage of all of your kit.  UPS use two ratings, VA (Volt-Amperes) and Watts.  See the simple 'cartoon' explanation at this sight (other sights are available  ) http://upsselector.eaton.com/Load You will see on that same page a calculator that you can use once you know the details of each piece of equipment you want to run off of the UPS.

As all your kit is down in your Obsy, you might want to print the UPS 'sizing' sheet out from this link https://powerquality.eaton.com/thoughtleadership/choosing-ups/size-a-ups.asp to assist taking notes whilst in there and then go back to the house and enter all that in online or do the calcs yourself on the paper.

Are you only wanting to run the kit in the Obsy on the UPS and not your 'main' PC back in the house as well?
As Lonestar70 said, "A lot depends on how much run time you require in the event of a power cut" as this will also be one of the main factors that will affect the cost of the UPS.

Hope that helps for now.

Rgds,

Chris.

[Skipper Billy]

Thanks Chris

I will print the sheet out and see what its pulling.

I am not too worried about the indoor PC as its now only connected with Remote Desktop so the obsy PC should keep going then when the power comes back on I should be able to relink it. Its unusual for the power to be off for more than 15 mins.

Thanks again.

[swag72]

I have a Salicru UPS and have everything connected into it....... mount, camera, lakeside, all sky, PC, 9" dewstrap at 100% ...... I had a power cut for 15 mins. Everything clicked in straight away and there was no lag that caused USB issues. I used about 25% of the battery for 15 mins.

[Skipper Billy]

Thanks Sara - will have a look at it.

[Jonk]

A proper UPS uses what's known as 'double conversion' method.

The ac power is converted to dc (first conversion) to charge the battery and supply the inverter, then dc back to ac (second conversion) via the inverter.

There should be no lag at all as the dc bus is always feeding the inverter with power.

1 wave of ac power is 1/50th of a second (20ms) 50 of these and voila, 50hz.

Any power sag of 10ms or more in duration may cause a pc to switch off, all proper double conversion UPSs should be compatible with the what's caused the CBEMA curve which states no sag in output voltage more than 10ms.

When looking for a small single phase UPS make sure it's a double conversion type and is compatible with the CBEMA curve.

Also, don't forget the limit of power for a standard single mains socket at home is 3kW (13A) at mains voltage so don't go looking for anything bigger.

A small single phase UPS will also not be for outdoor use and care will need to be taken when planning installation.

[RayD]

I use APC ones at home and work, and also have an Eaton one.  All are excellent but of course are premium brands so do come at a price.

You can of course use a battery, but be mindful of the fact that with a charger connected, whilst using it under load, your charger will default to bulk charge which can push your voltage up to over 14v, so not ideal and not something I would do personally.  The UPS also provides you with some mains surge protection when the power comes back on (the time when most tech failures occur) and generally will wait for the supply to stabilise before switching over.  In my experience with servers and many other bits connected to ours, and having had many outages, lag is not and issue and we have never had any equipment fail to continue working.

When selecting calculate your AC consumption as this is what they are rated at.  I doubt that will be anywhere near 10A so I would have thought something like a 750 - 1000Va will give you what you are after.

Edited November 3, 2017 by RayD

[Stub Mandrel]

Most UPS units are designed to cope with brief interruptions or give you enough time to do an orderly shutdown of your computer (typically s small business server) and avoid data loss. They are unlikely yo keep you kit going through a 30 minute sub.

[symmetal]

3 hours ago, RayD said:

You can of course use a battery, but be mindful of the fact that with a charger connected, whilst using it under load, your charger will default to bulk charge which can push your voltage up to over 14v, so not ideal and not something I would do personally.

You're right Ray so you need to be careful. The Ctek 'Multi' chargers can be switched into 'Supply' mode so that it gives out a constant 13.6V to enable the battery to be used while connected to the charger to keep it topped up. It effectively forces it into 'float maintenance' mode. The battery needs to be fully charged using it's normal charging mode before switching to 'supply' mode as it's not the best way to charge a flat battery. Other charger makes probably have this mode too but I only have experience with the Ctek one. I should have explained it more in my earlier post.

Alan

Edited November 3, 2017 by symmetal

[JOC]

Whether they can keep you going through a 30 minute sub very much depends on the load and the size of the device.  Having endured a complete hard disk failure and seen the problems it caused and living in an area that seems prone to power failures I invested in £800 worth of purpose made UPS.  It is quite brilliant and this year alone has got my IT kit through 6 power outages.  The computer doesn't even bat an eyelid, and all the other kit like monitors also runs fine.  I run 2 big flat screen monitors and router and the PC through it and it also shuts everything down when I turn off the PC thus saving on standby power.  It is quite simply the best IT related item I have ever bought.  I get about 40 - 60 minutes running everything wgich is more than enough to sort me out and if I am not around its software even closes the PC in a controlled fashion before the battery power expires.  It is so clever and I can recommend them highly enough.  Just get one bigger than you think you need and you should be fine.

[NickK]

I had an APC UPS for a home file server a while ago, very good idea considering the housemate pulled the power to plug in the vacuum..

Shutdown handling, the APC I had used a serial connection to alert the computer that the power (a) was on battery power, and (b) was reaching a critical level to trigger a graceful shutdown of the server. not many astro systems can invoke a park process, close the roof and shutdown the PC etc automatically.

Noise added to output, as the 12V systems we use are sensitive to noise finding the right inverter not to add noise into a AC-DC>battery->DC-AC->PSU->12V for a camera for example is going to be worth investment of the time to look for good options.

My (unqualified) thinking is that having a 12V battery being charged by a charger that leads to the 12V equipment is like having a capacitor over a motor in that it should reduce noise.. Especially with PWM style charging that limit/chop the current to shape the current delivery.

Lastly - deep cycle leisure batteries would be best. Although new cars have AGM style for the stop/start functionality.

Although a car battery.. I have a Bosch S5 100Ah that I have used for astro.. you can get two days of astro out of it however on the second day the noise level on the camera caused by the deeper discharge dropping the 12V line increased enough to be visible.

[JOC]

Would a deep cycle leisure battery possess the automatic switching ability of the specially designed units?  It sounds to me as though this is what is required.   I guess you could power everything directly through and therefore from the battery and just use the mains to keep the battery fully charged, which I guess would mean that the switch over didn't need to be managed, but if this was the way forward why would companies like APC (mine is also an APC) make the units specifically designed to perform as they do?

[Dr_Ju_ju]

they are designed to hold up the supply long enough for a 'control' signal to tell the connected devices to cleanly shut down.....

[symmetal]

The main reason I suggested having everything powered by a leisure battery rather than a UPS is it seems unnecessarily complicated and not very efficient to have during a power cut, a 12V UPS battery driving an inverter to generate mains voltage which can switch without glitches which then feeds a power supply to generate 12V which powers all the astro equipment apart from possibly a modest PC. A UPS is designed to power PCs for short periods only and not to generate 12V.

A simple inexpensive float charger (constant 13.6V) connected to a leisure battery to power all your astro gear and a small inexpensive inverter to power a PC (if a laptop isn't available) achieves all you want. No problems with having to have clean switching, and no problems with extended power cuts that may last all night.

A 12V battery is the best filter there is against power spikes, glitches and power supply noise. 

Alan

Edited November 10, 2017 by symmetal

[Physopto]

I have used an UPS  of the allways on type for over 20 years. It was produced long before the newer wave of USB types came out. So it does not shut down items of equipment as do the new ones. But it does the job. There is no time delay  when a power outage does occur because of it being permanently on. It is extremely heavy as its of the transformer type. I have replaced the 12 volt batteries several times over the years. It only can supply about 650 watts so can run without power for around 10 minutes if reasonably heavily loaded. BUT that is all I need to shut down my computer safely. 

If I could give any advice it would be yes get a good modern UPS machine with USB control, but only run the monitors off it if need be. Run your computers and scope,cameras etc., off 12 volts via a large LiFePo4 battery that is permanently on charge. 

Costly ,,,,,,, yes but the only way to virtually ensure a constant and stable power supply to your gear. We get so few good clear nights. 

Derek

[Stub Mandrel]

I use a leisure battery for camera cooling, a separate 7aH battery for the mount and my laptop which will do about 5 hours on a full charge.

If necessary I just hook up the laptop PSU and a battery charger if the leisure battery is a bit low. I recently bought a spare battery for the mount although it will run all night.

 

[Paul M]

My experience of UPS is purely industrial. We have some large units at work intended to support the PLC's, servers and clients during an outage. They do work as advertised but they cause more problems than they solve. When they develop faults (as they seem to too often) they disconnect the good mains supply too. So even though there is no failure of the mains we loose everything!!

There is a by-pass function but that doesn't switch during fault modes!

[Gina]

I haven't had any problem with UPS units and I've used them for years.

[Jonk]

6 hours ago, Paul M said:

There is a by-pass function but that doesn't switch during fault modes!

If you have large static double conversion UPSs and you have a fault on the inverter (overload, temperature, controls failure etc) then the UPS will automatically transfer the load to the static bypass (i.e. raw mains) IF the mains is in tolerance (voltage and frequency). If not, it will drop the load to protect itself.

Many customers assume a UPS will hold on to the load in all conditions, which is not true.

If you have rotary or diesel rotary then they probably won't transfer to bypass in a fault condition, just open their output to protect themselves.

Just out of interest, who's UPSs do you have?

The answer might explain why you have issues!