Modifying small UPS

[Nips]

Hi All,

I've seen some threads wher people have added batteries to the RCT 2KVA UPS with some success. I have a number of 220V LED lights I would like to power during load shedding - a total of 200W Max. Was thinking about doing a similar modification to an 800VA RCT UPS I have. The batteries in this one are taking strain anyway. Was thinking about adding on 1 (if the current battery is 12V) or 2(if it needs 24V) 105AH 12V Deep Cycle batteries.

Any reasons why it should not work?

 

[cavedog]

I'm also wondering about this. The thing I want to know is will the UPS be able to charge that huge battery and not damage it? I think the UPS will work fine on the battery though but have not ever tested this before but also want to try it out.

The small battery inside depletes so fast with a gaming pc,router,tv and console connected that it can't be good for the battery.

 

[Awesum]

The ups charger would be too small to recharge the battery. You might fry the charger circuit. It will work if you charge the batteries separately using a bigger charger.

 

[Dan C]

I got some noname brand 1000VA UPS with crappy batteries and want to do the same. But I will only do 2 x 35ah batteries , hope it will work and the charger is good enough.

 

[itareanlnotani]

The ups charger would be too small to recharge the battery. You might fry the charger circuit. It will work if you charge the batteries separately using a bigger charger.

Uh no. You wouldn't "fry the charger circuit".
The charger circuit is only going to put out what its capable of. The only issue you'll have is that the charger will take a long(er) time to charge a larger capacity battery than it would otherwise.
Should be fine if its for occasional use - eg every few days.

 

[BigEars]

Uh no. You wouldn't "fry the charger circuit".
The charger circuit is only going to put out what its capable of. The only issue you'll have is that the charger will take a long(er) time to charge a larger capacity battery than it would otherwise.
Should be fine if its for occasional use - eg every few days.

Agreed in principle. You will not "fry" the charging circuit. The problem is that most cheap 12V UPS's out there simply have a very basic charging circuit consisting of a LM317T regulator which just happens to suit a 7.5Ah battery very well with the IC's inherent current limiting ability of 2.2A MAX into any load. Rated at 1.5A for normal operation with a suitable heatsink. That's all sort of fine for the UPS for the way was meant to be used. Emergency back up only. All the UPS does it's whole life is watch the mains coming in and makes sure if there is a Brownout or Voltage surge that it handles it and so on......

The charging circuitry in the UPS job is to keep the float Voltage @ 13.6-13.8V. Nothing more. No cyclic use or anything.

Never designed to ever deal with constant (daily draining) like we sit with now.

Soooo, all that happens by adding a huge battery, is to make things worse for the already embattled charger that was not made for what it is being asked to do.

That's not the end of it though. Cheap UPS's are not meant to work more than a few minutes at a time.
They allow you time to shut your Computer down safely and that's it.

With all the mumbo jumbo out the way and if you are still following.....you probably know that this post has lots of hope for folks like you that like me want basic stuff to work when Eskom has it's regular daily fit

Two things you need to do first:

1. Check that your cheap UPS will only be powering SMPS related stuff...cooling fans and motors and transformers do not like a simulated Sine Wave supply. Get hot and damaged. Some quicker than others.
2. See if you have a friend/electronics person that is capable of disabling the charger circuit on your cheap UPS before you go any further. Very important you make sure that this is possible.

So if you are here and still reading...read on . Only good stuff to follow.

My situation: Got gatvol of unexpected daily load shedding (blackouts is my preferred term) around December last year. Things up and down. Never knew when and what ESKOM was up to to next.

I worked out my MAX load on the UPS would be around 200W for the stuff I needed to power. UPS rated at around 350W. Next I started looking around for a decent quality matched charger to charge the 65Ah SLA that I had purchased. Found this one which is well suited to my battery to charge it quickly after working: http://www.mantech.co.za/Stock.aspx?Query=372M0529and

Can handle anything from my battery up to say a 200Ah. 3 stage so it pulls the battery all the way up to 14.4V and then floats it @13.6-13.8v. But it is always changing and checking as the charging progresses. PDF file attached.

Next I found an old PC 12V cooling fan that fits nicely in the inside front of the UPS. Drilled lots of 3mm holes in front of the fan and mounted it. Now you do not want the fan running all the time because it is not necessary. The fan only needs to run when the UPS is running off the battery when ESKOM is down.

At the moment I am manually operating the cooling fan when ESKOM bails and the UPS has to run from battery. I am physically connecting the +lead myself. The answer though is a simple thermal switch mounted on one of the Mosfets heatsinks. They get hot quickly when the UPS starts working and the the fan will automatically kick in and cool things down. I have ordered this one: http://www.mantech.co.za/ProductInfo.aspx?Item=14M9575

So, other than that, this experimental setup is nearing completion.

Another thing I forgot to say is that I have been monitoring the charging/discharging with my Fluke to see where things stand at any given point so I don't drag the battery down too low when it is working with it's load...

Never rely on the UPS beeping furiously to warn you it is about to shut down....depending on the load you will already have taken it down into Deep Cycle territory. Always a bad thing. Regardless of battery quality.

More to follow. Hopefully pics too at some stage

 

[cavedog]

So how does one know what is the maximum battery size in terms of capacity the ups would be able to charge?

 

[Tovad]

Another problem is that the last cheap UPS I opened (a Mecer 600VA) had no heat sinks on the switching transistors. That would be ok for its original small battery as the battery would be discharged before the transistors overheated but with a larger battery this would not be the case anymore.

 

[BigEars]

Another problem is that the last cheap UPS I opened (a Mecer 600VA) had no heat sinks on the switching transistors. That would be ok for its original small battery as the battery would be discharged before the transistors overheated but with a larger battery this would not be the case anymore.

Good point. The one I modified is an old Powerman from around 2001. 600Va and small. But heatsinks on the switching Mosfets and also on the LM317T.

Very hard to give advise for all out there now. Just know I have to try though

 

[Dan C]

Can one charge batteries from a PC power supply ?

 

[BigEars]

Can one charge batteries from a PC power supply ?

I am getting into this again

Yes you can can sort of charge them. Something is better than nothing at all...but ultimately not enough.

Batteries (speaking SLA here) work hand in hand with the charger they are "married" to..

Not like a car battery that gets a quick boost from a charger in the garage...maybe 12 hours at most. Back in car and it starts. Chargers job is done.

SLA is a different kind of battery. Meant for different work. Constantly connected to the charger in most cases. Sometimes up to 20 Years depending on battery quality. That is why the charger determines battery life....

 

[Tinuva]

The RCT 2KVA UPS have a fast charger, which is slightly better than most UPSs. That is why the people currently like modifying that specific UPS and add 102AH batteries to it. Yes it takes longer to charge, but it charges fast enough for loadshedding here in cape town. That said, the batteries still get drained, and the lifetime still shortened.

Personally I have gone inverter route for now, but may consider the above if I really need to get something cheaper.

 

[BigEars]

At R56o6.00 it better have a good charger: http://coolsidecomputersystems.co.za/58-2kva-cps-true-online-3u-rackmount-ups.html

Talking cheap and basic here...a UPS mod that coupled with a good external charger gets the job done

 

[thehuman]

This is the online one tho
Will use more bateries too

 

[itareanlnotani]

Cheaper here - http://www.nivo.co.za/buy~rct.2000va.on.line.rackmount.ups~p33667

 

[thehuman]

4 x 100 ah bateries will be great on that online ups

 

[dunkyd]

Sadly most people have no idea what the difference is between a ups and an inverter....ask Mr Google.

 

[Dan C]

I am getting into this again

Yes you can can sort of charge them. Something is better than nothing at all...but ultimately not enough.

Batteries (speaking SLA here) work hand in hand with the charger they are "married" to..

Not like a car battery that gets a quick boost from a charger in the garage...maybe 12 hours at most. Back in car and it starts. Chargers job is done.

SLA is a different kind of battery. Meant for different work. Constantly connected to the charger in most cases. Sometimes up to 20 Years depending on battery quality. That is why the charger determines battery life....

No idea what you just said or typed

The reason why I asked was, I have a extra pc case with PSU.. maybe with some divine intervention I can put some batteries in it and an inverter

 

[mwill]

There must be thousands of guys who would like a solution to Eskoms present 'load shedding'. I've been looking around (forever) and have decided on a UPS/inverter/batteries as opposed to a generator. The generator is very expensive on fuel whereas batteries you can recharge from Eskom when the power is back up. In the event of Eskom going out for days at a time (a la Zimbabwe) your batteries can be charged with solar panels....one must weigh the cost of petrol for the generator to the cost of solar panels.

On Friday I looked at a very nice 600W (pure sine wave) inverter with separate 4Amp battery charger and 1x105Ah lead acid battery all neatly installed on 2 tray trolley for R5240 (Solar Equipment 041 453 7602). It looks good but should I have a 1000W system at 24volts for*when* I have to add solar panels.

(going the 'pure sine wave' at the moment because I don't want buzzing and lines on my Plasma TV as some posters have said)

 

[BigEars]

No idea what you just said or typed

The reason why I asked was, I have a extra pc case with PSU.. maybe with some divine intervention I can put some batteries in it and an inverter

Hi Dan

I am not far from you in BB (50 to 200KM's)...the reason I am trying to drum the charger thing into peoples heads is because it is the most important piece of kit you will ever buy for taking care of an investment...SLA and batteries are not cheap..

It's like such a basic concept to understand....but people somehow have trouble understanding it.

Bashed my head before everywhere....people are like...have a battery....gives power...good...

Nobody seems to ever take the charging part into serious consideration. Try this try that use this use that...
Experiment with that etc...

I learned the hard way in the SADF in 1981. I forgot but I am back on track after many failures after that.
Batteries are very different now compared to what we had then...not nice SLA like now...we had the best of the best at the time and they had a habit of leaking acid everywhere and trashing your browns (see my previous early posts).

Charger is the key to long life with SLA though. Stuffed really good SLA's up already after the Army with playing around and trying different charging methods. With SLA you either do it properly with a purpose designed charger....or leave it alone.

For what it's worth that is my view