UPS for MK3, full day of printing on battery  

Re: UPS for MK3, full day of printing on battery

Sure it's possible. The duration depends on the material you want to print and the UPS.
For example with this one you might be able to run it for 1-3 hours.

Re: UPS for MK3, full day of printing on battery

thanks for the reply, i supposed i should have added im printing with PLA.
I'd also be ok without using the heated bed.

as im simply using the printer for show and tell, i don't need to print at full speed.
do you think printing slower, would allow it to last longer on a battery? 50mm/s vs. 200mm/s

Re: UPS for MK3, full day of printing on battery

Maybe. Slower printing means less heat is required for the extruder.
I would also use a silicon sock and some kind of adhesive to turn off the bed after couple first layers. Should give you some more minutes.

Re: UPS for MK3, full day of printing on battery

why do I picture it like the Seinfeld episode where they tried to save George Costanza's Frogger high score?

I do have my mk3 and mmu2 on a cart. I could in theory try to bring it to a show whiles it's printing. I think we can do math and figure out how much power it takes.

Re: UPS for MK3, full day of printing on battery

it would be less expensive to buy a small generator /inverter set such as a honda to provide more than just a few hours of battery back up but if the battery backup is more what you want you can gang together a bunch of charged auto batteries and attach them to your UPS of the 1,500 VA size just add car batteries till you get the run time you need.

Re: UPS for MK3, full day of printing on battery

man.. now I want that 😀 I will look into it in a bit, I'm still at work. the thought of packing up the mmu2 while printing and bring it somewhere seems like a fun challenge. (I will not loose my fogger high score) :

Re: UPS for MK3, full day of printing on battery

Assume you average 180W power consumption while printing -- sometimes higher, sometimes lower. That is 7.5A@24V. A 90Ah battery would give you a bit over 10 hours. A pair of these, in series, would do the job: https://www.batterymart.com/p-sla-12v90ah-sealed-lead-acid-battery.html .

You will be much better off running directly off battery than trying to use a UPS. You would need a true sine wave UPS capable of providing a couple hundred watts for 8-10 hours. You are looking at a large rack mount unit, 3000VA or higher to get that kind of run time. Using a UPS will probably double the amount of battery you need as you have the inefficiency of the UPS converting DC to AC and then the inefficiency of the printer power supply converting AC back to DC. Using batteries directly bypasses all those losses. The one downside of running off batteries is that unless you want to do some more serious engineering, you can't just switch from AC to DC and back at will, like you could with with a UPS.

Someone else mentioned a small generator. That is certainly an option if the venue allows for it. A generator capable of continuous 200-300W output would not be terribly expensive, however, make sure it is a true sine wave output. Some of the smaller, cheaper generators actually use an inverter to generate the AC, similar to a UPS, and use the same simulated sine wave output of cheaper UPSes.

Perhaps something like this: https://purewavegenerators.com/product/purewave-dg-1500-digital-inverter-generator/?gclid=Cj0KCQiAkMDiBRDNARIsACKP1FE_yRXWcKbKQSs19YOkvgwW_D535yAJCLjRRxph0HjEmbZIyPUb-xUaAuvNEALw_wcB

Re: UPS for MK3, full day of printing on battery

Assume you average 180W power consumption while printing -- sometimes higher, sometimes lower. That is 7.5A@24V. A 90Ah battery would give you a bit over 10 hours. A pair of these, in series, would do the job: https://www.batterymart.com/p-sla-12v90ah-sealed-lead-acid-battery.html .

Well, a pair of this cost you $380, and you will get a voltage range between 23.8V and 24.8V depending on the charge level. And you need to get a charger.

Re: UPS for MK3, full day of printing on battery

Actually, you won't need a true sine wave inverter because the first thing the PSU does is rectify the ac to dc!.
You only need true sine wave inverters when there are transformers or ac motors involved. So that is one cost already lower.

Re: UPS for MK3, full day of printing on battery

Assume you average 180W power consumption while printing -- sometimes higher, sometimes lower. That is 7.5A@24V. A 90Ah battery would give you a bit over 10 hours. A pair of these, in series, would do the job: https://www.batterymart.com/p-sla-12v90ah-sealed-lead-acid-battery.html .

You will be much better off running directly off battery than trying to use a UPS. You would need a true sine wave UPS capable of providing a couple hundred watts for 8-10 hours. You are looking at a large rack mount unit, 3000VA or higher to get that kind of run time. Using a UPS will probably double the amount of battery you need as you have the inefficiency of the UPS converting DC to AC and then the inefficiency of the printer power supply converting AC back to DC. Using batteries directly bypasses all those losses. The one downside of running off batteries is that unless you want to do some more serious engineering, you can't just switch from AC to DC and back at will, like you could with with a UPS.

Someone else mentioned a small generator. That is certainly an option if the venue allows for it. A generator capable of continuous 200-300W output would not be terribly expensive, however, make sure it is a true sine wave output. Some of the smaller, cheaper generators actually use an inverter to generate the AC, similar to a UPS, and use the same simulated sine wave output of cheaper UPSes.

Perhaps something like this: https://purewavegenerators.com/product/purewave-dg-1500-digital-inverter-generator/?gclid=Cj0KCQiAkMDiBRDNARIsACKP1FE_yRXWcKbKQSs19YOkvgwW_D535yAJCLjRRxph0HjEmbZIyPUb-xUaAuvNEALw_wcB

thanks for doing the math stuff 😀

Re: UPS for MK3, full day of printing on battery

If your planning on doing this regularly, you may be interested in replacing the stock PSU with a Meanwell SD-350B-24 and run of two 12v leisure batteries in series to give you 24v (+- 4 v), the meanwell will actually run from 19v to 36v dc input but you don't want to over discharge your batteries.

Re: UPS for MK3, full day of printing on battery

Actually, you won't need a true sine wave inverter because the first thing the PSU does is rectify the ac to dc!.
You only need true sine wave inverters when there are transformers or ac motors involved. So that is one cost already lower.

You've never tried to run an autoranging, active PFC, power supply off a simulated sine wave and had the two of them not get along I take it. They don't necessarily react well. Some generally work, some work very poorly, some just shutdown. It depends on both the UPS design and the power supply design.

Sine wave output, all good here.

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Simulated sine wave output. Looks generally like a sine wave, just distorted. All sorts of noise in the spectrum. I would guess that most power supplies would work ok with this, though the dip at zero crossing might cause problems.

Another simulated sine wave output. This might also be referred to as a stepped sine wave output. This will probably trigger the power panic on the Mk3 if you have it enabled. The zero crossing is long enough that it looks like a power loss. In other supplies it may trigger a power fault shutdown. Intel server power supplies don't work well with this kind of wave form. This waveform is what you are likely to get out of most quality simulated/stepped sine wave inverters.

We also know that, from other threads, the Prusa supply is being run at its limits, especially when running on 120V. Even in a supply that functions with a simulated/stepped sine output, I would expect it to much rougher on the front end boost converter as the active PFC tries to follow the input waveform. Further stressing an already stressed power supply is not a recipe for success.

So your average, cheap UPS might work just fine, or it might not work at all. Plus, you still need battery capacity. Your average 450VA UPS likely has a single 12V 8Ah battery in it. After conversion losses, you'll be doing good to get 30 minutes of run time out of it. If you get a UPS with enough battery capacity to run 8-10h, its going to be a true sine wave unit anyway. If you bodge together an add on battery pack for a cheaper UPS, you've going to be buying big extra batteries and you might as well skip to levels of conversion and just run off the DC from the batteries directly, or as someone else pointed out, through a DC power supply. I definitely agree with the suggestion to feed a DC power supply from batteries. As noted, an SLA will range in voltage relatively significantly. I would actually expect the printer to work fine for PLA or other low bed temperature materials. The heating PWM will adjust the cycle for higher or lower voltage.

That said, if you are shelling out $350+ for batteries, an extra $40 or so for a boost converter is probably worth it. Take though two 12V/90Ah batteries in parallel and run them through a boost converter set for 24V output. https://www.amazon.com/gp/product/B01LWXI4IE/ref=ox_sc_act_title_1?smid=A1THAZDOWP300U&psc=1

No matter how you look at it, carrying around enough battery power for a full day of printing is going to be expensive, and heavy. It's hard to beat the storage capacity of hydrocarbons when it comes to some thing like this. A generator will be the cheapest solution, if it works in the venue. Otherwise you are looking at something on the order of $500-$600 minimum (once you add in a charger) in parts and then you have to put it together.

Re: UPS for MK3, full day of printing on battery

Just for the record: I'm using this one and it does work with MK3. The only issue is when power is switching from grid to battery, MK3 detects a power outage and is doing homing. Beside of that the printer is draining the battery without any issues.

Re: UPS for MK3, full day of printing on battery

I forgot about the power panic!. Point taken.

Re: UPS for MK3, full day of printing on battery

Cant you hook a bicycle and pedal for power? Show and tell would really be a hit.