Prusa (Mini) and UPS  

RE: Prusa (Mini) and UPS

I doubt it and do not think it will ever be supported; that would require it to know and "speak" the same language as the UPS to understand when to power down, and I don't think it's practical for them to start adding UPS drivers to the firmware given how many models are out there. 

RE: Prusa (Mini) and UPS

Unfortunately it doesn't support this, also I suspect it will never support this. But it's a really interesting idea!

RE: Prusa (Mini) and UPS

I know this feature from my NAS Storage. It waits e.g. 10 minutes in case of power loss
and in the first step is brings the harddrives in a parking position. And after some further
minutes (if power already lost) it switches off the NAS automatically without risc of dataloss.

I don't know if the API of FSP, EATON or APC are open, but it would only need the
indication "AC mains lost" ... "AC Mains is back". I think some UPS have also only a
serial signal output (hig/low level?).

Perhaps someone of the FW-TEam is reading it and set this feature on his todo-lsit for
one of the next FW versions. 🙂

happy printing ....
Timo

RE: Prusa (Mini) and UPS

Just connect that UPS to a raspberry with octoprint and go from there. I found this pluginwith a quick search.

RE: Prusa (Mini) and UPS

@orkelprint

Thanks ! I'll have a look

RE: Prusa (Mini) and UPS

This would be interesting to see, I actually posted something similar in a thread about power panic on the Mini. With the hardware that the mini and it's power supply has, there probably is no real way to implement power panic like on the i3 without involving a UPS and communicating over USB or Ethernet in the case of a UPS that can be Ethernet connected, the status of the power and to then pause the print after the UPS indicates it is in battery mode/hits a battery level threshold. There probably wouldn't be a need to build in support for a bunch of different UPSs, I believe a lot of them implement the protocol that APC uses. So building in support for APC UPSs would probably cover a large percent of the market.

RE: Prusa (Mini) and UPS

I do actually use a small APC ups on my mini, I don't expect it would print long on it, but the power rarely goes out where I am located in Florida for significant amount of time, power issues here are usually quick blips. If it does go out, it is going to go out longer than any consumer UPS could keep it running. Last major outage here was back when Irma came though Florida and I was without power for 4 days after.

RE: Prusa (Mini) and UPS

I have thought about building my own simple solution with two 12V Car batteries. Just to power through the print without any "smartness". On the other hand, power failures are super rare here.

RE: Prusa (Mini) and UPS

I have though about going solar with batteries.  

RE: Prusa (Mini) and UPS

I'd have to wonder how the mini would handle the voltage fluctuations. from the peak of being charged, to sagging as the battery discharges? Unless you put a buck/boost converter between the batteries and the mini to keep the voltage at a stable 24v. Likely wouldn't affect the electronics because it's probably already being bucked down to 5v/3.3v, but may throw off the heating? I'd suspect the heaters are probably just connected straight to the raw incoming 24v with just a mosfet to switch them on/off. May throw off any heating profiles the firmware uses as the batteries swing between around 27v at full charge down to around 22v at nearly discharged.

RE: Prusa (Mini) and UPS

You are correct with your assumptions. But since the temperature is controlled, this shouldn't be an issue. It will just adapt the dutycycle of the mosfet until the temperature is correct. The maximum reachable temperature will of course drop with lower input voltage, so there is that if you use special filaments that push boundaries of the printer.

I already took a look at everything connected to the 24V input. I checked the schematic and datasheets and the maximum voltage ratings of the components are mostly unproblematic for 2  lead acid batteries. I found one protection diode that might become problematic for above 28V (because its supposed to stop overvoltage). So I suggest not charging the batteries above that level (13,6V is a common cut off anyway).

RE: Prusa (Mini) and UPS

I have 2 100ah deep cycle batteries parallel connected here that I keep charged up for backup purposes/camping trips. The 10amp NOCO charger I use on them will push the batteries up to about 14.1 volts for a bit before terminating the charge. I would imagine their 24v charger for series connected batteries would bump it above 28v. So probably best to monitor what the upper charge voltage of whatever charger you are using. That said 180w buck/boost converters can be had for under $20 off amazon, at that price I'd probably do one of those between the batteries and printer just for the piece of mind. Not to mention it might give you more usable charge from the batteries if you really needed to keep pushing them for a print to get done, although that is very bad for the batteries. https://www.amazon.com/Converter-10-5-70V-2-5-58V-Conversion-Efficiency/dp/B07SFVF6PY

RE: Prusa (Mini) and UPS

Another thing to keep in mind with solar. Some solar chargers will do periodic equalization charges. I have a 20a Rover MPPT charger I use with a 120w solar panel for those batteries camping. If that were kept connected long term, the manual says it does an automatic equalization charge I believe it was every 30 days, and it cautions to confirm any connected devices can handle an equalization charge where it pushes the battery up into the 15-16v range for a period of time to desulfate the battery. I've never had the charger connected more than about 4 days out on trips, so I've never seen it go into equalization charge mode to see where the voltage actually sits.

RE: Prusa (Mini) and UPS

@d0ug

Always an issue.  Solar is never a 100% answer at this stage.  

RE: Prusa (Mini) and UPS

Posted by: @d0ug

Another thing to keep in mind with solar. Some solar chargers will do periodic equalization charges. I have a 20a Rover MPPT charger I use with a 120w solar panel for those batteries camping. If that were kept connected long term, the manual says it does an automatic equalization charge I believe it was every 30 days, and it cautions to confirm any connected devices can handle an equalization charge where it pushes the battery up into the 15-16v range for a period of time to desulfate the battery. I've never had the charger connected more than about 4 days out on trips, so I've never seen it go into equalization charge mode to see where the voltage actually sits.

Yep, when anyone does that, they should be very aware of anything they connect. Some normal 12V chargers do that as well, but usually not without telling them. The UPS kind of charge control usually just keeps the battery at 13,6V forever and thats pretty good for their health. A (buck)boost converter capable of 6-7 A would be the best option, that's true. If you don't have 2 batteries laying around, it's also cheaper, lighter, smaller. I think I will test the simple series configuration at some point though.

RE: Prusa (Mini) and UPS

Is there a good resource or calculator to determine how many batteries you need to run a device for x amount of time?

RE: Prusa (Mini) and UPS

Posted by: @cwbullet

Is there a good resource or calculator to determine how many batteries you need to run a device for x amount of time?

You should be able to convert amp hours to watt hours, and get an idea from that if you know how many watts your printer uses. I did measure mine once, and it was between 47 and 130 watts, for printing PLA, depending on the heaters and motors that are on.

But you will get some wasted power converting the voltages from a battery to what the Mini needs. Here's a site from a quick google that will convert for you:

https://convert-formula.com/ah-wh

RE: Prusa (Mini) and UPS

Also don't trust the Ah ratings of the cheap chinese stuff.

RE: Prusa (Mini) and UPS

According to https://help.prusa3d.com/en/article/faq-frequently-asked-questions_1932 the printers seem to average around 80-120w in use. That probably peaks to near the max wattage of the power supply which is I think 160w on the mini, since the heaters are going to be on at 100% to quickly hit the set temp, once at set temp the heaters are being PWMed to hold the temp, so the power draw will lower. Using the 120w figure, divide 120w by the 24v, to get 5amps of current draw. Then it is as simple as dividing the amp hrs of your battery by the current draw. 100ah battery with a 5amp load would give you 20hrs run time. However batteries like lead acid should never be drawn below 50% capacity. So in reality you have a 50ah battery, or 10hrs of run time. If you need more run time, get bigger batteries, or add additional batteries in parallel.