Leisure battery vs UPS

[Earl]

Im looking at having a Backup power supply for my Observatory in case of power cut. (it would be a real shame to loose the time of improved darkness)

It looks like a UPS is probably the best way to go, the drain of typical astro gear and a Laptop will be low. (mount 2 x ccd 2 x focuser x 2 dew bands)

Or could I just use a leisure battery linked up in some way?

[Sp@ce_d]

What about the dome/roof ?

I'm thinking along similar lines, I have a hefty roof driven by mains motor. UPS tend to be fairly pricey if you don't just want enough power to shut things down on failure. I was wondering about some leisure batteries & solar trickle charge. Course you'd still want a way to monitor supply and shut down before it gets flat.

[Tinker1947]

How often do you suffer a power cut, here in Norfolk i can't remember the last one.....

[Sp@ce_d]

What do you run the Obsy on Earl? I run the obsy on a laptop so there's always the battery in there as backup too for that.

Powercuts.. had one last week one evening for an hour or so.. lucky it was cloudy for a change

[szymon]

If everything is 12v, just run *everything* off a couple of big leisure batteries connected up in parallel (not in series, that will give you 24v and fry your equipment), and have the batteries permanently connected up to an Optimate smart charger (or similar).  This is what I do for my radio shack.  If the power goes out...the batteries just stop charging, but there is no effect on function.  When the power comes back on again, the charger kicks in and starts charging them up again.  If you have some 240v AC equipment which is only used rarely for short periods (e.g. dome control), then you could do the same but put an inverter in line for that equipment.

If all of your equipment is 240v you'll be better off going down the UPS route.  For longer outages, you could wire up a UPS to trigger a fuel powered generator; power goes out, UPS kicks in so that you transparently keep working, UPS fires up generator, and then switches over.

-simon

[pete_l]

What about the dome/roof ?

I'm thinking along similar lines, I have a hefty roof driven by mains motor. UPS tend to be fairly pricey if you don't just want enough power to shut things down on failure. I was wondering about some leisure batteries & solar trickle charge. Course you'd still want a way to monitor supply and shut down before it gets flat.

Be careful with running motors off a UPS. Some of them have a very hefty startup surge that could well exceed the capabilities of the UPS.

People are often warned about running a fridge off a UPS and a roof motor could fall into the same category.

[Earl]

We get brown outs here weekly at times, the dome has its own solarpowerd battery back up so thats covered.

[kev]

I suspect alt power may be wise this winter.

Sent from my iPhone using Tapatalk

[MattD101]

Have a look at these on eBay, the item number is 251358111195.

These are traction battery's and designed to run flat and charge up. You do need a good 20amp charger thou.

[perfrej]

UPSs have very marginal battery capacity. Go with Simon's suggestion. 12V computer, 12V this and 12V that, two AGM batteries (much more tolerant to deep charge than leisure batteries), a good charger.

/per

[Earl]

From what i have founf after an hour or so of googling, must of the nettop PC's are 19V?

[perfrej]

Yep, but there are several 12V systems out there. I use an MSI 6A19 in my boat, for instance, 12V fed.

You can add a 12-19V converter to th eequation - they're dirt cheap and work reliably. I have one in my Provence Obs as that computer (Asus Eeee-bx) is 19V.

/p

[thanders]

I prefer using a huge (110Ah AGM) battery and an 300W inverter with sinusoidal output. I keep the inverter and the battery in the trunk of my car and use an ordinary outdoor type extension cable to the scope and everything. Thus I can use the same equipment as operating from the mains. No exotic types of power supplies or DC/DC converters needed here.

Minimal electric hazard with the inverter since the output is floating with respect to ground.

During cold winter nights you can even make the power loss (≈15%) to your advantage. Just put the inverter in an isolated box together with the battery to keep the battery warm!  (At -20 degC the battery capacity is just 50% compared to tav 25 degC). Clear skies!

/Thomas