Inverter + battery VS UPS

I've just been asked to source some sort of backup power supply and was wondering is there any major disadvantage/advantage from going the inverter and battery route instead of a dedicated UPS?

They want to power PCs, network, printers etc for 3-4 hours.

bwana said:

I've just been asked to source some sort of backup power supply and was wondering is there any major disadvantage/advantage from going the inverter and battery route instead of a dedicated UPS? They want to power PCs, network, printers etc.

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I'm using the Inverex inverter + battery. Problem I get is that it doesn't act as a true UPS in as much that if the power is cut, my computer reboots losing any data that I might be working on. The switch over time, from mains power to battery, is not sufficient to keep the power constant.

A dedicated UPS will only have enough battery juice to give you time to save your data and power down. If want to run your whole network for a 2-4 hour loadshed, go the inverter route.

Go both routes: Small UPS with each work station to keep the workstation running when the power goes down, and most importantly, to filter spikes which occur when the power comes back on.

Then have a longer term capacity solution like a battery/inverter setup or a generator feeding the UPS's

Ozymandias said:

A dedicated UPS will only have enough battery juice to give you time to save your data and power down. If want to run your whole network for a 2-4 hour loadshed, go the inverter route.

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What he said: it's a capacity thing. IOW while a UPS will stop the power dip and keep your PC up, it won't have the run time ...or a charging circuit, much less batteries (they ARE those teeny li'l things in there!) to deliver juice for that long.

Maybe a 2-tier approach: the equipment all connected to an inverter with small UPSs on the PCs that need it to handle the change-over? Note that if you're using laser printers, it's a bad thing to connect one to a UPS as their batteries can't deliver that kind of demand (visualising some APC Back-UPS devices I've seen: they've got black sockets for the PC/screen power and a grey one for the printer)

Thanks for the input

Just been looking at http://www.altpower.co.za. Their prices look significantly better than what I paid for my battery system. They stock a nice wide range (300W - 5000W).

Problem if you just use a Inverter and a battery, is you have to manually connect the system after the failure, and then manually charge the battery afterwards.

The Intellipower type UPS's can run a lot of equipment, switch over instantly so you dont go off, and recharge automatically when the power comes back on.
Basically plug and play


You also get pure sine wave units from some distributors here, but they cost a LOT more.

Inverter: Sqaure Wave (they call it modified sine )

UPS: Depends on brand but APC line interactive or better almost exclusively have sine wave output.

Another plus for UPS's are they are made according to strict IEC standards and switch over time must be within certain parameters provided the topology is Line Interactive.

Furthermore UPS's can usually also correct frequency and voltage dips/peaks (within constraints) but will switch automatically to battery mode if the power is unacceptable. Not sure if the inverter will do it, but I'm doubtful.

And finally you can with a little bit of effort effectively add huge extra batteries to your UPS to add more time so to me that is a non-issue.

Only thing against UPS is cost, but since most Inverters are selling for outrages prices in SA anyway I don't see the benefit.

I currently have a Tedelex IntilliPower2 Inverter running my PC, with a 1000va UPS in between -works perfectly - the Inverter switchover time is 20-40ms, so the UPS takes care of that...

Take a 600VA UPS and add a 105Ah Battery, you should get a much longer time. Only Problem is the charging as the UPS charger wont be enough as it only runs a 7Ah battery. One Option will be to disconnect the big battery every time it runs flat and charge it using a bigger charger, or leave the big battery connected to the ups and connect the charger.

I've seen this at two of my clients, one client that disconnects the big battery and charges it and the other that leaves it on constant charge all the time. I'm planning on experimenting to see if I can do something like this for myself.

kaspaas said:

Go both routes: Small UPS with each work station to keep the workstation running when the power goes down, and most importantly, to filter spikes which occur when the power comes back on.

Then have a longer term capacity solution like a battery/inverter setup or a generator feeding the UPS's

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Yep, for long run times a genny + UPS is the most cost effective solution - very long run time from UPS alone can be expensive due to battery costs.

Just done that for a client after the building's genny popped various bits of kit.

I bought a Microtek 1400 watt Pure Sine Wave UPS. It doesn't come with batteries, instead it has to be connected to 2 deep-cycle batteries.

The switch-over time is the same as any good ups.

It cost me R2750 + R2000 for the two batteries = R4750.

Inverter battery

Hi,
I bought the Tedelex Intellipower 2 inverter.
1 x 12V battery - imput= 5.5 amps output = 4.6 amps
They claim that this unit can run anything up to 1000w.
They also claim that the backup power lasts for 6 -8 hours.
My TV was on for 3.5 hours when the battery ran flat.
I feel this conflicts with the specs. given that the TV power requirements
is only about 300w.
Maybe the 6 -8 hours refers to running only a 20w globe, but off course
the prospective buyer is not informed.
I require to run my TV, PC and 100w fish tank items for the duration of
load shedding. Obviously this unit cannot cope.

It depends on the battery you have connected, the simplest way to calculate the amount of time you will have is using the Amp hour rating on the battery (abbreviated Ah).

The voltage times amp hour rating = the total amount of power the battery can store for a given hour. Therefore if you have a 100Ah battery and it's a 12volt battery you have 1200W Hour. In other words if the Inverter was 100% efficient (it isn't) you'd get 4 hours on a 300w appliance. If the appliance needs 2400W of power you have 1/2 hour, etc.

My point being the unit might promise 5 hours of operation but it depends on the battery. Also a UPS for instance thats rated at 600VA will usually have a power rating of 400W, therefore it can in reality only provide 400W of power. Assuming NO load on that unit it would take the UPS 4 hours to recharge the battery, once again assuming 100% efficiency (It definitely isn't).

Barrymore said:

Hi,
I bought the Tedelex Intellipower 2 inverter.
1 x 12V battery - imput= 5.5 amps output = 4.6 amps
They claim that this unit can run anything up to 1000w.
They also claim that the backup power lasts for 6 -8 hours.
My TV was on for 3.5 hours when the battery ran flat.
I feel this conflicts with the specs. given that the TV power requirements
is only about 300w.
Maybe the 6 -8 hours refers to running only a 20w globe, but off course
the prospective buyer is not informed.
I require to run my TV, PC and 100w fish tank items for the duration of
load shedding. Obviously this unit cannot cope.

Click to expand...

The IntelliPower2 unit is only rated to 600w continuous power with a startup spike load of 1200w - the IntelliPower4 is 1200w and 2400w respectively.
What TV do you have - LCD, Plasma, CRT?
If the TV is 300w, the fish tank 100w and the PC approx. 200w, then you're about to exceed the capabilities of the unit, and it'll probably shut down.

I am running the same unit, with a 74cm CRT TV (155w), DSTV decoder (36w), HDD DVD Recorder (110w) and 2x 8w energy saver lamps, and it runs the full 4 hours of a loadshed -- I left it on for longer the first time we used it and it started giving up after about 6 hours 47 minutes.

I think you're plugging in too much on the unit, and it's reducing the run-time considerably -- you can of course try and add another deep cycle battery or three in parallel (must be in pairs apparently) to extend your run time on the unit, but you are pushing it close to it's limit...

Inverters generally are about 95-99% efficient, depending on the make and model and price, etc. They leak somewhere around <0.1A of current, (which is not really that much at <23W).

It doesn't matter how you connect your batteries (except that on a 12-V inverter or UPS they HAVE to be in parallel, not series). The more batteries in parallel, the longer the duration that they last. One thing that is important to remember when discharging a deep cycle battery is not to run it completely flat as this inhibits the ability to fully (about 95%) recharge and also lessens the number of charge cycles the battery can handle. Try not to go below 30% capacity...

Inverter /UPS

To Gnome and Howardb thankyou for making the effort to reply.

Initially my Electrician advised me to buy a 20amp inverter from Tedelek rather than a
generator, as the fluctuating voltage could damage my computer.
Tedelek informed me that I had to buy thru their agent, a video hire shop in Durban.
I made phone contact and was informed that the inverter came in two sizes, 12amps and
24amps. I calculated that 12amps would be more than enough to run my computer, TV (54"CRT ) and my microwave (1600w power consumption)

I ordered it.
When stocks arrived I collected it, still sealled in it’s box, and only after unpacking it at home
was I able to read off the attached label. “output 1000VA / 600W”
This conflicts with the ads I have seen stating that both the Intellipower 2 and 4 “runs any product under 1000W.”

I also now realise that the agent did not know the difference between amps and watts, as my
reference to my amp requirements was met with him quoting the battery voltage.

Teljoy have been advertising for rent both 12 and 24 v units.
Their ad has pictures of both units with the specification for each listed.
The 12v unit (mine) “runs for 6 to 8 hours.” The ad then has pictures of all the devices that
can be connected, namely “ 2 x 60watt light + a 54 or 74cm TV + a home entertainment
system + a DVD + a satellite dish + a DSTV decoder”

I have also seen in ads for this 12v unit that a small microwave can be connected.????
How small I ask? If the power consumption is say 600w, then the microwave would have to have a output power of ?
I don’t believe there to be such a small microwave on the market.

All in all I believe lack of knowledge by the selling agent plus false advertising
information has caused me to be in this predicament Too late - I shall have to make do with what I’ve got.

]Please- how do I determine what the battery’s amp hour rating is so I can calculate
what I can run. My previous post stated that while my devices are connected, only my TV
was on, when the battery went flat after 3.5 hrs. Fish tank lights were off and PC were off.
Today, during a two hour outage, only my 100w fish tank devices were drawing power. My TV, modem, dish decoder etc. were inactive, in standby mode with only LED's on, yet presently the battery is still re-charging, 2.5 hours later.
Confusion rules.

Hi Barrymore - most welcome.

The unit can apparently run a small microwave oven - I would take a guess at 600w unit for approx. 30 minutes max, before the IntelliPower2 unit shuts down. I really would not try and run a microwave off this unit, only on the 24v IntelliPower4 unit - the smaller microwaves are running out the shops at an alarming rate, and they are becoming more difficult to find these days...

It definitely sounds like a huge lack of knowledge on the sales agent side, as watts and amps are obviously very different on the rating scale, and I would take it further with their MD if I were you.

The unit you have is the 12V 600w/1200w 1000va unit, and it has (or should have) a 102Ah battery - mine has this, as I checked it after I got it home - took off the cover carefully and looked at the battery label in the case. I'm beginning to wonder if the "agents" have replaced it with a 40Ah or 60Ah battery, as those times don't sound right at all.
On our load-shedding last night, I had the 74cm TV (155w), 2x 8w lamps, DSTV (36w), my laptop (65w) and other electronic components on standby (hifi, DVD recorder and VCR), and it easily saw us through the 4 hours - I turned off the wall power before the power came back on, and left the unit to run off the battery, and it only started giving me a low battery alarm after a further 3.45 hours, which equates to 7h45m in total off a 102Ah battery.
After this test, I switched on the power at the wall and the unit stated charging - I went to bed and got up 4 hours later and the unit was still charging (the fan was still on), and it finally finished charging to full capacity an hour or so later (the fan switched off automatically)

Open the battery box unit (5-6 screws each side) and check the battery - let us know what's in there... it could also be a dud battery, but should not be the case if it's brand new...

The problem is your inverter is going to have a hard time recharging the batteries but I'll post the math and explain as best I can:

First of all to determine the Amp hour rating, check the battery, it should be physically written on the battery somewhere, ALSO make SURE it is a deep cycle battery.

As for the math it's quite simple:

The total amount of power a battery can store is:
Amp Hour Rating x Battery Voltage = Watt Hour Rating.
So lets say you have a 100Ah (Ah = amp hour) 12v battery, that means it stores 1200watt of power for one hour. (12x100 = 1200).

So from there to calculate the actual time your appliances will run you take the total LOAD that you will be running, for example a TV of say 300w and a computer of 400W. That is a total load of 700W.

So your single 100Ah 12v battery will last 1200/700 = 1.7 hours.

If you connect many batteries in series the voltage increases so if you connect 2x 100Ah 12v batteries you have 100Ah 24v which is 2400W which would give you 3.4 hours on the load above. ONLY connect the batteries in series if the Inverter supports 24v else

Parallel, which for 2x 100Ah 12v batteries would give you 200Ah 12v which also translates to 2400W. You can find many source on the inter that explain how to connect batteries, circuits, etc. in series/parallel

As for the Amp rating of the Inverter they obviously don't know what they were talking about because a 12amp inverter could mean anything (12amps on which voltage?).

Also disregard the VA rating Volt Ampere and Wattage may seem the same (indeed because watt = Volts x Amps) but the VA rating is what is usually used to rate a transformer, so basically the transformer (and perhaps certain other parts of the circuit) can handle a load of 1000VA but the total load is still restricted to 600W.

Also on the calculations above, a electronic circuit is never 100% efficient so best to assume 5-10% loss.

EDIT: Also remember that, best case scenario, if the inverter is running of the wall socket it can recharge the battery at full load which is 600W but chargers are grossly inefficient so it'll probably take 3-4 times as long to recharge VS. the amount of power you got out of it.

inverter/ups

Thanks guys,
I will check the battery's Amp hour this weekend.
In the meantime I will relate two "unusual" events relating to this issue.
When I bought the unit, the young salesman helped carry the heavy box to my car, where we placed it in the boot, LAYING IT ON IT'S SIDE.
24 hours later I came to remove the box, only to find that the boot mat and the box was saturated with battery acid.
I used it in this state until it showed signs of deterioration before the agent
advised me to take the unit to a repair shop where they were to change the battery. They actually replaced the entire case as acid corrosion was evident inside the case. I was assured that the entire case and battery was new.

Today on arriving home from work, the unit was beeping madly. I was confused as no load shedding had taken place.
The maid had decided to do the ironing in the lounge and had plugged the iron
into the circuit leading to the unit.
What I have learnt from this is that even if the power is on, and the unit is not running, it must still not be overloaded.
Presumably if it is switched off, this would not be the case.
Cheers.