Battery Backup Power Supply

After printing a 13 hr part and have the power go out at the 9th hour.. I am poised to buy a battery back up for my printer.
Anyone using them? If so , what size? Wattage?
How long does it last if the power goes out?

If you look at websites for companies like APC they can give you wattage ratings and run times. Most small consumer units are only designed to give a few minutes of runtime for a pc and send a signal to the pc to shut down or hibernate. If you want to run a printer for hours you may be looking at a very large and expensive (more than the printer, certainly) commercial unit.

It would be interesting if someone made a ups that signaled ramps or Pi to pause, run the fans and safely shut down, maybe insert a bookmark or save a line number from the gcode, then giving you a prayer of possibly restarting and finishing when you get back to it.

It's always hooked up. A 550. Not sure exactly how long, but probably close to two hours while my FF Creator Pro is printing. If my power goes out for more than about 15 minutes or so, I usually start my generator anyway. Regardless, the printer never loses power...

Here's a quick back of the envelope calculation/what I would do in this apocalypse scenario (read: I don't recommend doing this in this way, there's no regulation to keep the battery at 12VDC, could be more could be less, could destroy your printer.):

A quick an very general google search says most car batteries have a capacity of 50Ah (Amp-Hours)

I think our printers need something like 11A for the bed and 2-5A for the hotend to lets say 15A @ 12VDC

Car batteries are 12VDC, so (50A-H)/15A = approx 3.33 hrs of run time from a car battery.

*grabs popcorn*

I figure if I can get at least 2 hrs out of one, id be content. Most of the times the power is restored with in a few minutes anyways.

I just picked up this one with my prime account.
http://www.amazon.com/gp/product/B00...?ie=UTF8&psc=1

Very nice! Should get at least an hour out of it.

UPS capacity from your link: Full Load 425W for 3 mins , Half Load (212.5W) for 45 mins.

12VDC*15A = 180W

http://www.amazon.com/Tripp-Lite-SMA...dp/B009TZTGWK/
This runs the machine the printer is plugged into and the printer plus a couple other small draw items. I own 3 of them for various computers or electronics not always for the battery backup but also the line conditioning so brown outs and voltage spikes don't blow stuff up too.

not bad, its come out to $162 with prime..

Not to be a naysayer but you can reprint about 5kg of failed parts for the same money. I can see it would be super annoying if the power blips a lot though.