Dealing with UPS questions

[Paul Haese]

Now that I have a remote system I thought it was time to get an uninterrupted power supply (UPS).

I spent some time looking around and came up with a Eaton 3000va unit with a delivery of 2700watts.

Today whilst commissioning it I noticed that the system was using about 165w with the system fully energised including the roof and the camera holding the temp at -25c. It then said below that it was good for 89 minutes.

Now my question is this, why would a system of less than 1 kw prevent the ups lasting for 3 hours? What am I missing here?

Just for more info.
Mount PME
Camera QSI
MHP powering camera, rotator, dew heater and focusor via a regulated power supply of 13.8 volts and 20 amp supply.
Computer - desktop with 400 watt power supply.
Roof controller by scope dome.
Monitor ( that would be off)
weather sensor AAG (it has a heater too)

Thoughts?

[acropolite (Phil)]

At the end of the day the power rating is irrelevant, what matters is the (usually) miniscule battery capacity in the UPS.

As an example, an average small 600VA UPS has about 7 amp hours capacity at 12 volts, in other words at best around 80 watt hours, at full load you could expect 5 minutes before the UPS died.

If you want longer run times pick a UPS that can have an add on battery pack or better still one that you can fit your own batteries.

[Paul Haese]

I can buy extender batteries which are 1000 each so for another 2 grand I get 4.5 hours of run time. I guess what I should really do is setup the system to report that ups is in play and cancel the run and shut down the system.

[g__day (Matthew)]

Dumb question - but can you easily add big (e.g car or boat) batteries in parallel to the battery backup of a say an online UPS or are things likely to blow up?

Point two - the PC running a 400w A/C PSU... If you could switch to a DC Powersupply I am told you would significantly extend the battery life of the PC - as the DC -> AC -> DC conversion really losses power.

[Paul Haese]

I don't know the answer to your question Matthew.

The dc power supply would be good if I was not running off mains most of the time. Can the dc power supply work with an ac system? Or is the fact that everything now runs off the ups makes the system a 12 volt system?

[Peter.M]

I was under the impression that a UPS was used to protect the system from dirty power. Surely you wont be using the UPS isolated from mains power. If your concern was shutting the roof to protect gear in the event the obs loses power I would have thought that in the (hopefully) rare event that this happens you wont miss the extra data from that night.

I would set it to shut as soon as mains power is gone if there is an option for that.

[Paul Haese]

Those are my thoughts too Pete. As yet I don't know how to do that. Can CCDAP handle this or do I need to script that? I am assuming the usb connection from the UPS to the computer and installation of software can inform the computer that mains power is lost. Maybe the scope dome software can handle this???? I will have to look into it.

[Peter.M]

Just an idea, what happens if your cloud sensor loses power? If it loses power and CCDAP cant get a reading it might close the dome anyway. If that is the case you could just run the cloud sensor through mains and the rest on the UPS.

Then if the system loses power the cloud sensor being lost will be the queue to close the dome and the rest of the powered things will be on the UPS so they will have the power to do so.

My quick reading online is that CCDAP can be set to go into shutdown mode if it dosent get a signal from the sensor for a specified time. That would mean my idea might work.

[Paul Haese]

Actually that is a good idea. I have the setting set for 4 minutes at the moment. I will look into this a bit more.

[jase (Jason)]

Also forget about the UPS software automatically shutting down your PC. Sounds good in theory, but when you are running remote, who's going to power the system back up again when mains is restored?

If your PC remembers its state when power is lost, you don't want to change this to off by shutting it down. Leave it running. I have an small APC UPS. Similar to Phil, it only runs the system for five or so minutes. I didn't buy the UPS to be able to operate with no mains power, I bought it to ensure I could obtain the cleanest power and protect the equipment.

When operating in a dome whereby you can close the observatory shutter without needing to park the telescope, you've got a major advantage. In the case of a ROR where you must park the scope in order for the dome to close, you simply need enough power to achieve the task. If you can't do this task in 89 minutes, you've got major problems.

Keep it simple. Protecting your equipment is #1 priority, in the end, nothing else matters. The hassle of relaunching software and starting your imaging plan once mains is restored is insignificant compared to a telescope exposed to the elements due to a observatory that can't close due to no power.

[Paul Haese]

Jase I agree, protection of the gear is paramount and the roof closing is the priority. The current configuration is that I only have the TSA on the mount and the roof clears all the gear doing this, so the roof can close without the scope being parked.

Do you know how to get CCDautopilot to sense that power is down and close the roof as a result?

[Bassnut (Fred)]

Originally Posted by Paul Haese

Jase I agree, protection of the gear is paramount and the roof closing is the priority. The current configuration is that I only have the TSA on the mount and the roof clears all the gear doing this, so the roof can close without the scope being parked.

Do you know how to get CCDautopilot to sense that power is down and close the roof as a result?

Peters idea is the simplest and surest way to close, and it doesnt need to PC at all to do so. Power the cloudsensor from mains (not the UPS) and connect its seperate hard contact output straight to the roof close input.

One small thing, if your roof is heavy and rolls well, the AC controller driving it may use regeneration back to mains (UPS output)for braking on close. A cheap UPS might not like this backfeeding. Its unlikely to be a problem, but just dont buy the cheapest no-name UPS you can find.

[ZeroID (Brent)]

If you have the model number just go to the Eaton website and check out the specs. ( My wife sells them in NZ ) But you may find the 3000 actually runs several 12v cells in a series configuration and output is 24v to the inverter unit.
Not sure how you woould go about connecting car batteries into that configuration and the cells need to match, ie UPs uses gel cells, not lead acid. Charge rate and sensing of charge state ( very imortant) will not work.
Failure in this regard leads to fire and meltdowns, I can vouch for that !!

Re dirty power ( Peter M ). UPS CAN fix dirty power if it is a double conversion unit that is online all the time. Most smaller UPS are offline, ie they monitor hte incoming power to the load and only intervene when power fails.
We run adouble conversion UPS (3000 ) to our sound and TV system. Mainly for power protection but it also puts out a perfect sinusoidal waveform at exactly 230 vac so my 12' sub doesn't produce weird little clicks and any ac 50hz hum noises.

[Paul Haese]

Thanks guy,

I got a double conversion unit and it will need to have the expansion units. I will not be wiring things up to non compliant power units. Too much money sitting in that observatory for that.

Fred, I have the weather sensor hooked into the roof controller already so I agree that sounds like the best strategy. I will give it a try when I am down there next time. I might even use another 9258 unit just to power that straight from mains. That way I can turn off the weather remotely when I finish an imaging session. Not sure if leaving the weather sensor on all the time is the best idea.