UPS + Flooded Lead Acid (not SLA)

[domwild]

Hi,

The following cheap system has been set up:

Accupower Select 2000 UPS, 1500W, 2000VA, 36VDC in, 240VAC out to four IEC sockets for four PCs.

Three 600 CCA car batteries, CCA = cold cranking amps, an Aussie description, been told to divide by six to get Amphours roughly, so I have about 36VDC @ 100Ah.

Measured AC voltage whilst on mains: 244VAC

Measured AC voltage whilst off mains: 234VAC

Question 1: Been told a cheap US$3 DMM will be confused by square waveform and read 180VAC, can I expect this UPS to be a pure sine wave model??

UPS floats batteries to 40.4VDC, this problem has been pointed out in this forum before as this only means 13.5V during charge max. This is the SLA float voltage I presume.

Q2.: Is it easy to find the trimpot to get closer to 14.7V as written on one of the batteries as the max. charging voltage??

Once fully charged the UPS claims via LED lights to be able to light a 60W 240AC light bulb for 90 minutes. Q3.: Does this sound reasonable??

A 850W 240VAC 4" angle grinder did not get started as expected and after a warning beep signal switched the UPS off.

Car batteries at rest read 12.3V, 12.4V and 12.5V. Two are older and one is brand new.

Whilst off the mains, the UPS drops the voltage every two seconds by 100mV with the 60W light attached, so the Volt meter reads: 40.4, 40.3, 40.2, etc.

Q4.: Is such a behaviour expected from a cheap system which does not have SLAs connected??

Thanks.

 

[AbyssUnderground]

Car batteries are not a good choice for a UPS. Car batteries are designed for just 5% discharge and no more whereas SLA's are capable of up to 80% discharge. Do this to a car battery and they won't last long at all (maybe 20-30 cycles).

Q1. It would be best to look up this model on google and see what information there is about it. The manufacturers website should tell you if it is pure sine or mod sine, but I would assume mod sine as most UPS's are.

Q2. There may not be a trim pot but if you're good with electronics you could probably figure out what to change. Look for some pots and see where they are on the board. It could hint as to what it does. I usually fiddle and see what the outcome is but Ive learned that can be a bad idea in most cases as i can never be sure of its original position...

60. w bulb for 90 mins on its orignal battery may be reasonable yes but with bigger batteries it would be even longer than this.
    
36. v is the nominal voltage so 39v would be 13v per battery. Once it gets to about 37-38v it should slow down significantly. It drops quickly because you're removing surface charge.
    
    

Hope this information helps.

[Norm]

In answer to your last question....I certainly would

expect such behavior from such a setup.

What is your goal? To light up a 60 watt bulb?

I have a cheap ($40)SLA battery with a 250 watt

($18) inverter that will run a 24 watt CFL ($3).

 IMHO you need a more realistic goal...yours

seems to be rather cloudy....Yours seem to be

oriented towards cheap with the exception of

your time and labor...which is never cheap.

           but maybe its fun?

          ( :>) Norm

[BruceDownunder]

Hi Dom.

I have been running an APC 1000 XL (around 840 watts,I think) for nearly 5 years now . No fan,disconnected the buzzer,turn it on in the morning ,turn it off at workshop closedown time .

It runs all my lights ,stereo,CB radio equipt. big dc power supply ,big dc-dc inverter and flood lights if I want.

Won't run drills Etc.

I've never had any trouble and yes,I get 180Vac on an el cheapo dmm ,,but 239 V ac on my Fluke DMM.

And,,it cost $5 ,like new,tossed the buggered batteries out and it goes-never has stopped.

I now have Accupower(2) and APC's(4). all were cheap as chips ,like new.

Got 2 big 1500w ex-Telecom units that I would like to run ,but they are 96v dc-my system is 24vdc-

Now ,where do I get a 24vdc--to 96vdc inverter .

Having fun

Bruce

[jimovonz]

That Fluke wouldn't be a 'True RMS' meter would it???

[BruceDownunder]

Hi Jim ,, dunno, I've 4 "Fluke"'s ,from various jobs-they came with everything needed to do the installation packed in crates-The helicopter used to lower thr materials onto the site in the jungle,everything you possibly needed,everything,even generator and fuel.

Then after we finished , everything left over just got left brhind-still there today,i guess.

But I did hear that the chopper pilots were scrounging if they "happened" to fly past a site.

The Fluke's probably cost arounf $400-$600 .

Bruce

[domwild]

Thanks for the answers. The Emmerson website does not give me any details of this model and have not even answered a request to sell me the manual and/or software.

The 60W light globe was a load I could think of and I thought the indication of 90 min. for this load was a linear affair, meaning a 180 W load would then run 30 minutes.

Thanks.