UPS/Battery backup thoughts and questions
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@DocTrucker Morning Wes.
PSU is 24V. I'm showing VIn as being 23.7 so a little low. Too low to recharge a battery I'd guess so for sure I'd need an external charger. Do you know if you can get 24V leisure batteries or are they all 12v so I'd need 2 in series?
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We use Phoenix Contact Power supplies and 24vdc ups’s for our pump station controllers. They have to continue to power the modem and RTU for compliance reasons for up to 30 days. The batteries are 2x standard 12v lead acid batteries connected in series. They would be your best option. They are tidy wee din rail mount units. If you get the Quint version they have various comms expansion cards that you can get all sorts of information out. They do also have various io on them such as battery mode that you can set up as an input into the RPi. The trio is an integrated power supply and ups version that is slightly cheaper also by Phoenix contact.
Regards
Sam -
10A Quint (you can use your current power supply as they are 24in 24 out)
https://www.phoenixcontact.com/online/portal/nz?uri=pxc-oc-itemdetail:pid=2320225&library=nzen&tab=1
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@deckingman I've found 12v planet a gold mine of information for the truck.
https://www.12voltplanet.co.uk/
Winch and starter currents can creep and make you fastidious in lesser wiring!
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Ian, if you cool down the bed, your parts may warp and pop off... For PLA, I don't heat the bed anymore: I have a LockBuild surface, and it sticks very well with hair spray. I already printed 300x300 parts without issue.
About 24V PSU, I have one of these Quint stuff (a bigger one), and plan to use it with two 12V batteries. We used them at work, and it works fine.
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@fma As per my OP, it takes an awfully long time for the bed temp to drop to the point where parts might fall off - longer than a UPS could reasonably be expected to run the rest of the printer.
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@deckingman said in UPS/Battery backup thoughts and questions:
I suspect the answer to the following question is a big NO NO but what would happen if I simply connect a big 24V deep cycle leisure battery in parallel with the 24V PSU?
as hinted to you'd only utilize part of the capacity of the batteries as the full charge voltage is a few volts over the nominal voltage. however you could run the duet at full charge voltage of up to 28.8v and have full use of the battery. but it would charge just fine back to 24v if used with 24v psu - the catch is a fraction of the capacity
meanwell makes psu's with built in battery backup, but you'll still be using the cell voltage not regulated to nominal voltage. i use a few of them with 12v access controll setups, cheap and works well and even din rail mounting.
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@deckingman You could always look into surplus Cell site backup systems where you have 24V Rectifiers that supply a float charge to the batteries and the batteries run the equipment we used to use 24V Systems and there are still a few in service even now.
Suppliers I know have are POWEC, Inverses, Harmer and Simmonds and Erskine.
Trouble is that they tend to be bulky.
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@bearer Thanks and that makes sense about a fraction of the battery capacity. But doesn't a the inverter in a UPS suffer the same limitation?
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@Dougal1957 Cheers Doug. I'm not too worried about bulk. The plan is that I'd instigate this after I've first moved the printer into my garage so I'll have more room and it won't matter what it looks like.
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@deckingman Next time I see any on site I'll take a pic or 2 for you
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Hi,
The simplest approach would be a UPS of needed capacity to handle the outages.
Is that just too expensive?
Frederick
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@fcwilt said in UPS/Battery backup thoughts and questions:
Hi,
The simplest approach would be a UPS of needed capacity to handle the outages.
Is that just too expensive?
Frederick
As per my OP if you read it, you'll see that is the solution I put forward. But it just seems a bit daft to have an inverter converting from DC to 220V AC at around 85% efficiency, then a PSU converting that AC back to 24v DC with another loss due to efficiency. Why not cut out the "middle men" and just have DC backup?
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Unless I missed it, we are missing a key fact from this discussion: What is the pattern of outages at your printing site?
For example, at my house, I have a fair number of mains outages that last less than 3 minutes. Often just a few seconds. In the three years I've lived here, outages that last more than a few minutes have only happened twice. And both of those were 8+ hours. A UPS that could keep my 1300+ watt mains bed heater for 8+ hours is certainly physically possible, but it is more bulk and expense than I desire.
Therefore...
I've elected to put my smaller, 12 or 24 volt bed, printers on a small UPS. My printer that is big enough to have a mains bed, the logic (and motors and so forth) are on another small UPS, the bed is not UPS, it is mains only. Obviously, the printer has to have to power cords.
This has worked very well. All short outages have been perfectly covered, and I've not had a long outage during a long print. Maybe someday I will; if it happens, Cest La Vie.
So let's ask it as a question: What is the typical pattern that you are trying to mitigate? Have you considered covering only the "90th percentile" (using that term very loosely) outage occurrences ?
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@deckingman said in UPS/Battery backup thoughts and questions:
As per my OP if you read it, you'll see that is the solution I put forward. But it just seems a bit daft to have an inverter converting from DC to 220V AC at around 85% efficiency, then a PSU converting that AC back to 24v DC with another loss due to efficiency. Why not cut out the "middle men" and just have DC backup?
There is engineering elegance to do it directly, bypassing the 220V stages. There is operational elegance, and robustness, in purchasing a totally "off the shelf" solution and just plugging it in and having it work.
Me, personally, on a 'backup' system, I'm going to go for operational elegance & robustness every time.
Having said that, Telcos have done this for ages. They run ALL THE TIME on 24V from batteries (or is it 48V? I don't remember) and their incoming utility and power distribution keeps those batteries charged.
Assuming that Lead Acid batteries are used, "simple parallel" at 24V is NOT a good strategy. Lead Acid batteries will lose capacity rapidly if held at their nominal voltage for long periods of time. They will not "be there when you need them" in terms of ability to deep discharge.
Instead, they need a battery charger designed for lead acid batteries. One that will 'charge' vs. 'float' at proper voltages. These voltages are all within the operating range of a Duet. So a three way connection of battery charger, batteries, Duet should work just fine.
With one caveat: Some battery chargers are also "maintainers" or "de-sulfate" devices. These put out very short spikes of voltage WAY WAY above charge/float, to stop (or even remove) plate sulfation. Obviously, such spikes should not go into a duet.
Summary: I, personally, would not worry about the losses and would just use off the shelf components. If you do choose to go 24V battery, it seems OK to connect charger/battery/duet all in parallel. Pick a charger that does NOT de-sulfate.
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@Danal most telco stuff now is -48Volt supply but in the earlier days of Cell sites it was +24V and there are still some of the kit around the batteries tend to be deep discharge Gell type cells and the control systems are designed to disconnect the batteries from the output when they fall to a certain voltage to save the cells (They can be expensive to replace)
Doug
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We run quite a few Harmer & Simmons modules in the field (for 48V telco stuff
).
These are quite expensive but last very long (we have some modules older than 20 years).
I would personally go for "operational elegance" as Danal nicely describes because dealing with DC charging and batteries can be dangerous stuff (I've experienced a 24V battery explosion (due to bad maintenance), it was not pretty...) -
@whosrdaddy said in UPS/Battery backup thoughts and questions:
We run quite a few Harmer & Simmons modules in the field (for 48V telco stuff
).
These are quite expensive but last very long (we have some modules older than 20 years).
I would personally go for "operational elegance" as Danal nicely describes because dealing with DC charging and batteries can be dangerous stuff (I've experienced a 24V battery explosion (due to bad maintenance), it was not pretty...)This of course is very true I to have seen this the Harmer and Simmonds I have used where all 24V Systems using SM24-50 or SM1800 rectifiers but they do tend to be huge.
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@deckingman this Quint UPS’s are a 24vdc in 2vdc out. So you power supply is providing the power to the ups, which obviously charges the batteries and also runs your system. When power is lost, it switches over to batteries. There is no conversion between Ac and dc past the initial power supply. As far as I am aware with them, you can install as big of a battery system as you like. Having separate power supplies means you don’t have to replace yours
