A UPS is an Uninterruptible Power Supply that provides backup power when the main power source is lost. Questions on repairing commercial ones are generally off topic.

learn more… | top users | synonyms

0
votes
1answer
22 views

Sizing battery cables

I'm confused about the sizing of the battery cables for a UPS system, When the battery is discharging the voltage decrease and current increase to a maximum value (which depend on the end of discharge ...
0
votes
0answers
13 views

What's the best way of using LiFePO4s in a UPS?

I have built a server using a Raspberry Pi and a couple of USB HDDs. The HDDs are 3.5". The server system also includes a network hub and a router, so I need 5 V @ 2A for the Pi, and 12 V @ 4A for ...
0
votes
0answers
44 views

UPS symbol for schematic

I'm using QElectroTech to draw a one-line diagram of an electrical installation that has some UPSs installed. The software has no UPS symbol for one-line diagrams. The one available is single phase ...
3
votes
2answers
121 views

How to keep a 9 volt micro-controller ON when where is no electricity for some minutes?

I want to keep an DCcduino clone of arduino uno ON where there is no electricity for 5-10 minutes with a 9 volt battery. Is there any way to do it without ups because it costs too much?
1
vote
3answers
95 views

Two identical DC power supplies in parallel for redundancy?

I'm trying to design a power backup system for my saltwater aquarium. In short, the system will be powered by a 12VDC power supply while the mains power is on. On power failure, the system will ...
0
votes
1answer
46 views

help modifying picoUPS

I found a simple commercially available uninterruptable power supply picoUPS-100. The manufacturer does not provide the circuit schematic, however, the principle block diagram looks like that: I ...
1
vote
0answers
49 views

5 volt small UPS design (review request)

I'm designing small 5 volts UPS that would allow me to run on battery or 5V source. If source is unavailable, step-up module takes power from battery. If this 5V source is restored, then this source ...
0
votes
0answers
34 views

Operating different current batteries in parallel with a UPS

I have a 24V UPS and I use a pair of 12V batteries in series, each with the same current rating (130A). Often I charge the batteries with an external 24V charger to achieve a faster charging time. I ...
0
votes
1answer
53 views

Is it wise (safe) to connect a Bench Power Supply to a UPS?

The power at my place is generally reliable but a few times a year we have an outage or brownout. With my luck, it will happen just when I am testing something on the bench (microelectronics). I am ...
-1
votes
4answers
62 views

Surge protection not working on a home projector [closed]

I have a problem with power supply and no idea of how to solve it. The whole system consists of a projector, an AV receiver, a subwoofer and a PS4. Around 800W. Early when I just got the projector it ...
0
votes
1answer
85 views

Would it be possible to use two UPS in series?

Would it be possible to use two UPS (uninterruptible power supply) that deliver same voltage (230 VAC) and same power (eg : 2200 VA) in series? The first one would be connected to the main. The ...
3
votes
2answers
219 views

Supercapacitor Emergency Power Supply UPS

I'm considering hiring an electrical engineer to design an emergency power supply for use in embedded devices. This power supply only needs to hold ~15 seconds of charge (enough time to safely shut ...
1
vote
1answer
71 views

modify 700VA UPS to power 65Watt Laptop Adapter for hours instead of minutes

I have 700VA UPS which I had bought in 2009 to power my Desktop Computer.It can power desktop(17" CRT monitor,CPU cabinet ) for 5-6 minutes.It has 7Ah battery(only 1), charging and inverting circuit ...
0
votes
6answers
200 views

Will a capacitor do the trick?

Today power went down in my house and although my computer is hooked on a very powerful UPS AKA backup power soure, it shut down as soon as the power was off and started back up seconds later. The ...
0
votes
0answers
50 views

Power supply recovery

Suppose I have a DC load that needs to be switched to another power supply if the main supply fails. Given two 12V lead acid batteries, is there a circuit for switching to the backup battery when the ...
0
votes
2answers
99 views

Security with multiple electric lines

I have created a system using arduino where it controls 5 different electric lines. For example: Line 1, Line 2, Line 3, Line 4 and Line 5. What arduino does is, it turns on the Line 1 if it has ...
5
votes
3answers
376 views

Why does a UPS need an isolation transformer?

Why would we need isolation transformers before and/or after for a UPS system? What are we trying to protect, and from what? I have read that it has to do with grounding and neutral but I didn't ...
0
votes
1answer
693 views

P-chanel MOSFET series configuration

Good day I'm busy designing a small DC UPS to run some appliances when the power goes out. I am, however, having trouble with an element in the battery switch-over circuit. I decided on using a ...
0
votes
3answers
41 views

16/18 VAC to 5 VDC UPS

I'm new here so please bear with me. I'm planning to replace my old central alarm system with a new raspberry pi, which takes 5 VDC input. My old central uses a separate 230 VAC to 16/18 VAC ...
0
votes
1answer
67 views

Can tranformerless inverter topology be used in UPS with a regular battery (12V 7Ah)?

While searching for transformerless inverters in the IEEE site, most of them seem to be about grid connected Photovoltaic inverters. Removing transformers will increase the efficiency at the cost of ...
4
votes
5answers
328 views

seeking help identifying small buzzing transformer from my UPS, or advice on how to silence it

i have an APC brand UPS installed inside another project, and have just recently powered it up for long durations for the first time. and i've picked up an annoying buzz in a small transformer on the ...
0
votes
3answers
120 views

Why could a UPS device need of a microprocessor? [closed]

I have read about some UPS devices that are microprocessor-controlled, and I would like to understand the fundamentals of needing such a microelectronical device like a CPU for what it just seem a ...
2
votes
1answer
137 views

Rechargeable battery Backup circuit

I have seen this rechargeable battery back up circuit on web.The resistor is used to limit the current.The diode in series is mainly to prevent the back feeding the power supply during battery ...
1
vote
1answer
129 views

Transistor UPS circuit

I am trying to create a UPS circuit purely to provide battery power when main input power is lost. I think I've figured out part of the circuit that stops the battery input when the main power is ...
0
votes
1answer
61 views

Does one of the battery failure damages the UPS DC capacitor bank? [closed]

Last day i found the DC capacitor bank of the 300kva UPS was burst/damaged.Upon further inspection one of the battery in the battery bank found damaged .My doubt is whether the failure of battery can ...
3
votes
1answer
173 views

Raspberry PI UPS

I needed solution to keep Raspberry PI B+ running in case of power loss. So made following power backup circuit: It works, however, when it runs from battery, a bit too much voltage is dropped in ...
0
votes
1answer
133 views

Creating an Array from 18650 cells to work with Solar/Wind/UPS [closed]

I originally was asking about the progress of this thread: Creating a large 18650 Array Below is the same information I posted there since I was asked to repost as a new question. Summary: use 18650 ...
1
vote
1answer
94 views

Grid changeover switching

I am designing a changeover circuit that will switch the power of attached appliances between two electricity providers. The two AC mains are of 220V RMS voltage and 50Hz frequency sine waves. The two ...
0
votes
1answer
114 views

UPS and Inverter power supply sync question

I'm new to this but want to ask this question If i'm having a 3 phase inverter with a battery backup system. does it requires it to sync with the utility power? if yes how long that sync can take or ...
0
votes
2answers
163 views

How to modify USB battery pack to function like a UPS?

I bought this USB battery hoping to use it as a uninterruptible power supply for a Raspberry Pi 2. I researched it, and users said it could be charged while also powering devices...just what a UPS ...
1
vote
2answers
943 views

How to charge an AGM battery fast?

I have a 12V, 200AH AGM battery. The maximum charging current recommended by the manufacturer is 50 amps. Now, I need to connect two AGM 12v batteries in series to connect to the input of my 24 volt ...
0
votes
1answer
155 views

Is an older APC backup UPS likely to be the source of blown fuses in new lab equipment? [closed]

I have new laboratory equipment plugged into an older APC Back-UPS XS 1000. It derives all of its power from this backup system, which in turn is plugged into a regular power outlet. The lab equipment ...
1
vote
0answers
193 views

USB battery charger and GPIO power supply schematic for Raspberry Pi

I'm trying to design a circuit in Eagle to provide reliable + safe battery power to a Raspberry Pi via the GPIO pins. The requirements are: Accept power input via micro USB (separate from the Pi). ...
-1
votes
0answers
49 views

Designing a DC UPS system [duplicate]

My requirements are: I need a UPS system which supplies power to a 9 volt modem. UPS should Charge 12v battery (SLA , charging curent 800ma), and it should have overcharge/discharge protection system ...
1
vote
1answer
80 views

What kind of testing equipment is used for UPS (>15 kVA)?

I work at IT division of a bank. Currently we need to order some Double Conversion True Online UPS ( Uninterruptible Power Supply) systems for our our new data center. The required ratings for UPS are ...
-1
votes
1answer
260 views

Designing 12v DC UPS

My requirements are: I need a UPS system which supplies power to a 9 volt modem. UPS should Charge 12v battery (SLA , charging curent 800ma), and it should have overcharge/discharge protection system ...
0
votes
2answers
511 views

Can I safely run a LED light bulb from a UPS? [closed]

I think I blew a capacitor (heard a pop sound) inside a UPS when I plugged in a 29 watt LED light bulb. It still works, but now the UPS is really slow to switch back to AC power after a brownout. ...
0
votes
1answer
48 views

600 watts regulated DC for 3 seconds [closed]

In my area, due to frequent storms, there are frequently short mains power cuts lasting a second or two at most. While the shorter several-millisecond outages don't usually cause issues, the longer ...
3
votes
1answer
317 views

Creating a battery backup unit

I live in a area with frequent power failures lasting up to 5 hours. During this time I would like to power my router so that I can still use the internet with my phone/PC. I've looked at UPS ...
1
vote
1answer
125 views

Intel Atom board (DN2800MT) power supply, can I add battery?

After reading through 20-something posts about 'car/12V/power supply/computer' I've still not found a definitive answer to what I'd like to try here. If this turns out to be a dupe after all, my ...
0
votes
1answer
297 views

Supercapacitor circuit modification

I am looking to build a UPS circuit using supercapacitors. I have seen a number of circuits posted online, and a lot of them look very complex (some using lipos, some using NiMH etc). Please note, I ...
2
votes
1answer
297 views

Prevent desktop from switching off when power inverter switches from mains to backup [closed]

I'm using a desktop computer over a power inverter that's connected to a 12V lead acid battery. When the main power supply fails, the inverter switches to battery backup and can power my desktop for ...
1
vote
3answers
5k views

Extending the backup runtime of a UPS with an external car battery

I'm looking for a simple/inexpensive way to have a longer power backup time. My fist thought was putting 2 cheap UPSes in parallel. But I quickly found it's not that simple. You would need another ...
1
vote
1answer
615 views

Is it possible to connect a UPS in parallel with the mains?

Short version: When a UPS is plugged in to the mains, is it possible to plug the UPS output back to the same mains? Will that work as an emergency power backup for the mains circuit? Longer version: ...
0
votes
1answer
164 views

Fast Switching For UPS

Well I don't even know how to call this question, but the point is. I am making a DC UPS, and I want to be able to quickly switch from the wall supply to the battery supply, and I don't think a relay ...
5
votes
2answers
1k views

Relay not switching immediately from switching power supply to battery backup

WARNING This project as currently described is badly flawed in a number of ways that are liable to lead to complete failure of the equipment. As it is stated that it is intended to be used in a life ...
-1
votes
1answer
623 views

How do we detect when Power Source from EB to DG

Is there a way we can detect if power source switch from EB to DG? Are there any circuits or alarms already there in market which triggers when the power source changes from Normal Power Supply to ...
3
votes
2answers
407 views

Low voltage DC Supercap UPS Design

Most generally I'm looking to design a UPS for a low power DC device given higher voltage AC current, with storage handled by a supercapacitor, or a bank wired in parallel. For my specific case I'm ...
1
vote
2answers
550 views

Measuring internal resistance of a battery while it's being charged

I was startled to hear that there are devices out there that can measure the internal resistance of batteries, in circuit, while the batteries are being (trickle-)charged. For example, Hioki markets ...
1
vote
3answers
359 views

Rate my Rasberry Pi UPS

I've made simple schematic for a UPS for Raspberry Pi. It contains a 12V Lead Acid Battery (40Ah), 5V LM7805 regulator and some capacitors. I'm supposing max 1.2A load from Raspi. Should I add ...