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Author Topic: Ups battery help  (Read 2782 times)
Dca
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« on: June 15, 2015, 07:52:15 PM »

Hi
I have inherited a small ups that did have two 12v batteries inside, both of which are now dead.

I have a single small car battery that would run a few things for an hour when we go camping and was wondering if I can effectively join the terminals together to use this ups?  Or does the ups effectively need two separate 12v circuits to convert into a combined 240v?

Pictures attached in this and the next post.

Thanks in advance for any help received.

DCA


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Dca
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« Reply #1 on: June 15, 2015, 07:53:08 PM »

More pictures


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biff
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« Reply #2 on: June 15, 2015, 08:11:04 PM »

Hi DCA, Could you give me the UPS ,s brand name and model.
    First let me say that you need to be very carefull where you put your fingers in that UPS. It may be disconnected from the mains but the Capacitors might still have enough life in them to shock you to death, (stop your heart) As regards the voltage, Looking at the wiring,the batts look to be done in parallel but don,t trust that,get out your volt meter and check. or write down the name and chase them up online,that way you will be sure. Most Ups that I have worked on with 2 batts has always been 24volt but you need to be sure.
  You can usually switch these ups,s over to external batteries of a higher capacity but some do not stay alive for more than 20 minutes, (the news models)
                                                                           Biff
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jonesy
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« Reply #3 on: June 16, 2015, 11:43:27 AM »

That PCB is used in Powerman Back UPS - is that what it is?  I'd guess a 1kva.
The transformer is wound for 2 x 12V, as it looks like each of those white battery wires end up there.  The black ones are probably commoned to chassis.
I think you're out of luck for using 1 battery.  Before you splash out on another battery, power it up with some borrowed ones (assuming it will 'black start' ie no mains in present) and see what the no-load drain is.  It can be awful.  Typically it's around 24W for a 24V ups (1A per hour), meaning that the original 7Ah batteries would only last around 6-7 hours on no-load. Put a 50W load on, and you'd be taking 2+1 A per hour.  Two 50Ah car batteries might go 50/3 hours = 17hours  (they're effectively in series, so it's 1 x 50Ah) but taking a car battery that low regularly would reduce its life significantly.
The other think to bear is that the ups was designed to power the load for a few minutes and shut down. Those heatsinks are massively undersized;  I ran my 1.4kva unit with the lid off and 2 large fans when the breadmaker (800VA - so that's about 40A@24V) was going, and they still hit about 80C. I've also destroyed one when the fan failed. So what I'm trying to say is do some tests to avoid disappointment.
Even at 10/night, a hook up is cheap!
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Dca
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« Reply #4 on: June 19, 2015, 08:51:30 AM »

Thanks for the prompt responses, sorry for the slow reply.
The brand is Power Inspired and the model VIX 2120
1200VA

http://www.powerinspired.com/vix2120-1200va-uninterruptible-power-supply-p-755.html

From the previous comments, I think it's heading for the recycling. Especially as I have just found out it's square wave on battery mode.

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biff
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« Reply #5 on: June 19, 2015, 09:20:40 AM »

Most ups,s strive to give a good clean sine wave form,
                                        Most of the the equipment that they are set to protect are sensitive to modified sine wave so it is unusual for them to be square. However if you have had the scope on it and saw the wave then you would know, There have been excellent input from some of our better informed members,who said that the pure sine wave is not altogether necessary and that certain modified waves really work well. If it is in working condition,hold on to it. Find out more about it and use it to learn how to install external batts. So when you do find a UPS that you like,you will already know about the capacitors, the starting up sequence, how to start from cold if they are not cold starters. These ups,s can be a very useful thing to have about. They can provide enough light and power to run your C/H pump during a power outage. Just a thought worth considering. It is about 800watt and not to be scoffed at and could be designed to lose very little power while on standby.
                                                                Biff
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Dca
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« Reply #6 on: June 19, 2015, 07:33:17 PM »

Thanks Biff and Jonesy

Indeed my secondary purpose for the ups was to run our CH in the winter if we had a power cut. I think that these were reported as likely for the last winter, but we didn't have any.

Do you know how I can determine if my newish fandango boiler boiler can run off batteries by this.  The last thing I would want to do is destroy a PCB when the whole country is looking for a plumber to get their heating running. It's an Ariston E System 30.

Also I guess that I could charge the batteries whilst drawing power?  I assume that the electronics would not just pump out 260v because the batteries were at 14v rather than 12v. Charging would be off the car or contraption bolted to the lawnmower.

Cheers
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jonesy
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« Reply #7 on: June 21, 2015, 10:58:49 AM »

I think, like Biff, that it's unlikely to be a square wave output, but the manufacturer does say it on the web site!
The main problem with the square wave output is the fast rising edges; basically they will destroy in a pretty short time (hours) the switch mode power supplies that are common place in most consumer electronics.  I wouldn't risk it.
The ups would regulate the battery voltage to a nominal 230V, so having a charger connected would probably be ok. 
If you really want a back up, buy a small suitcase genny.  The main advantage is that it will run all day, as long as you have petrol.  A UPS will give out after a few hours, and you'll still need to buy new, expensive batteries every few years. The main problem I've had with, say, lawnmower engines is they are not very efficient and very noisy.  I have a 16HP/500CC ride on that uses nearly 2 litres per hour.  The car uses 5 L per hour idling, according to the on board computer.  A suitcase genny (I just looked at the Clarke IG2200) will give you 1400W and use 1L per hour, and pretty quiet.
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