Looking for a 24vdc UPS solution

I need to create a 120v UPS from 12v batteries and a charger/supply device that has some intelligence behind it. I have one from Sola that comes close to my goal but shuts down at 22vdc batt voltage and there is no adjustment for that setpoint. The batteries reach 22v relatively quickly and the plcs will run below that voltage.
The goal is to get maximum runtime.
I have found no other options except expensive prebuilt cabinets designed for traffic signals.
I would appreciate any pointers to other devices you all know about.

look at schematics for a 120V ac drive, a set of batteries to equal 169Vdc tied into the dc buss of the drive, then build battery pack for your amp hour needs. I have done this back in the 80's for a UPS, you might want to see if you can find an older analog drive as they are easier to trick out.

I have purchased an integrated UPS from Phoenix Contact that provides 24Vdc power from a UPS battery power supply that charges from US 115Vac.

I have no part numbers at hand.

Maybe not what you need but from what I read on your post it could be.

Automotive stores sell devices often called inverters, that plug into a cigarette lighter in the car, that can give out a mains voltage supply, and larger versions that would need connected directly to a battery
Then what would be needed is to keep that battery fully charged

You would need to take of the charging side yourself, and it depends on the watts you need. But on the output side look at a DC/DC converter with a wide input range. The SM3320 here takes any input from 10.6 to 32 and will give you a stablised 24Vd.c. output until the battery gets below 10.6. The 200 watt version means you would have 8Amps available.

http://www.whatpowersupply.com/products.asp?cat=DC to DC Convertor

I would build my own and that way get what I want. The batteries would be in the range on 100 amp/hour - last quite a while. Have given away trying to find what I want regularly these days - easier to build my own.

use a voltage transducer to monitor the battery voltage then setup your plc to hold a relay that feeds power to the plc closed until it gets to your low setpoint.

Hello Watrboy;
Have a look at the DC-UPS line from Siemens Sitop, we have had to use them for some of our projects, you should be able to find a model that could support your project:
https://www.automation.siemens.com/mcms/power-supply-sitop/en/dc-ups/Pages/default.aspx

Hope this helps,
Daniel Chartier

Building my own is what I have been doing though maxketcham's ideas is a bit larger scale that I had in mind.

What I started with long ago was a 24v PLC, a 12V radio and 2 Automotive batteries with 2 12v chargers, one across each one.
The PLC was wired across both batteries and the radio was wired across one.

This worked except for the battery life expectancy was greatly diminished because of the uneven loading and the coarse regulation on the battery chargers. That combination led to battery ruptures and swelling prematurely. Limiting resistors and diodes were used in various interations but nothing satisfying came of this.

Next design was a single 24vdc charger across both batteries and a DC-DC converter powering the 12v Radio. This is like Bryan G suggests, works pretty well and is the current design (though I am not using it to supply 24vdc, only 12vdc )

I have also tried commercial office style UPS's which work surprisingly well. But since they arent suited for the outdoor envronmental range I am limited in deploying those. They also fail in the OFF state.

I am looking for better options now as I build new cabinets. i.e. since the panels have 120vac most of the time should I lean toward 24Vdc to 120VAC inverters powering everything? Then what do I use to switch the load from normal power to UPS power. A relay isn't fast enough to prevent a transient and power should really be switched to the zero-cross of the sine wave anyway. I was hoping there was a device built for this purpose that I could just buy and hook to whatever bank of batteries I chose. Bigger batteries = longer runtime.

Th ideal Device should charge the batteries and have some feedback that the PLC can monitor to advise of battery condition, on battery power etc.

I will look at the Siemens parts dchartier sent but at first glance it looks like you need to buy thier batteries and thats the part I really want to avoid.

heres another option a plc that will take 12volts:
http://www.automationdirect.com/adc...pandable_Micro_Brick_PLC)/PLC_Units/D0-06DR-D

Strictly an AB shop, dont have that option

Strictly an AB shop, dont have that option

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That keep you from being able to think outside the A-Box
Must be Boring there!

I will look at the Siemens parts

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better just look!

bce123 said:

That keep you from being able to think outside the A-Box. must be Boring there!

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Not really.

Location: State of Denial
LOL