Inverters

[HR Solutions]

3x - I cannot have a genie due to our office park. I have to have an inverter, therefore I am looking for guidance on what to get to last me up to 4 hours.

[ians]

Your quote for that unit must have been around R5000?

[HR Solutions]

Your quote for that unit must have been around R5000?

Yes .... And I'm wondering how long it will last ? Ie will it last 4 hours ?

[CLIVE-TRIANGLE]

I have discovered that re-charge time has now also become critical. That info sheet refers to between 6 and 12 hours, which is probably ok.

I don't know what my UPS is supposed to be, but when we had occasional power-outs it allowed us more than enough time to safely shutdown our NAS (network attached storage) box and then it would happily keep our routers and access points going for about two hours.

Now, when the power goes off it does not hold the NAS box for even long enough for me to shut it down; I would say 3 minutes and it's dead. The unit is less than a year old so I assume the battery is ok. Many (probably most) off the shelf UPS are "online" and so the net charge is minimal. With these rolling load shedding power offs, it has no hope of reaching full charge before the next out.

I mention this because most commercial units are made for developed countries where power failures are the exception, not the norm, so that issue is suddenly a factor.

The previous units I had were supported by a standby generator. I suspect the generator's voltage regulator was really dodgy because it killed the UPS units pretty quickly. I changed from desktops to laptops with external monitors and wireless keyboards and mouse so that the laptops' battery became the UPS and at least the computer hibernates and ultimately does a soft shutdown when that battery gets low.

I am afraid there is no way out; if it is important that you work through power outages and more importantly, you value your data, you have no choice but to throw money at it.

If your desktops are recent powerful beasts, the power supplies are almost certainly 300 watt units and if so then I doubt the unit you posted will be adequate.

[Justloadit]

Hi Clive,

I am in no doubt that the battery in your UPS is dead. This happens when low cost batteries are used. Most suppliers, to keep the cost of the UPS as low as possible to compete, use the low cost batteries.
You will need to open the inverter, and replace with what is called a deep cycle battery. Will probably cost 3 times more than the low cost units.
The main problem with UPSs are that they continuously trickle charge the battery, and this kills the battery over time. One should also at least once a month run the UPS off the battery, so that the battery can cycle and keep the electrolyte going. Also for a full charge, you need a 24hour cycle.

With respect to the generator killing UPSs, it is simply too small for the application, making the generator hunt around the 50Hz excessively, making the UPS switch in and out attempting to maintain a constant power to your computers, this hunting, causes excessive voltage to be developed which takes out the UPS protection (MOVS or surge arresters).

If a generator hunts up and down, stop and get a larger one. Just remember up here on the highveld, you lose 40% of the generator capacity because of the thin air, add to it that it will be a Chinese made in whcih the specs have been inflated, and divide the rating by 50% to get a rough idea of its true capacity.

[CLIVE-TRIANGLE]

Hi Clive,

I am in no doubt that the battery in your UPS is dead. This happens when low cost batteries are used. Most suppliers, to keep the cost of the UPS as low as possible to compete, use the low cost batteries.
You will need to open the inverter, and replace with what is called a deep cycle battery. Will probably cost 3 times more than the low cost units.

I will certainly give that a try. This is kind of like a packaged unit with a battery very similar to those attached to alarm systems. Do you get "deep cycle" batteries in that format?

The main problem with UPSs are that they continuously trickle charge the battery, and this kills the battery over time. One should also at least once a month run the UPS off the battery, so that the battery can cycle and keep the electrolyte going. Also for a full charge, you need a 24hour cycle.

This I am sure is part of the problem. Our shedding schedule so far has come every 18 hours.

With respect to the generator killing UPSs, it is simply too small for the application, making the generator hunt around the 50Hz excessively, making the UPS switch in and out attempting to maintain a constant power to your computers, this hunting, causes excessive voltage to be developed which takes out the UPS protection (MOVS or surge arresters).
If a generator hunts up and down, stop and get a larger one. Just remember up here on the highveld, you lose 40% of the generator capacity because of the thin air, add to it that it will be a Chinese made in whcih the specs have been inflated, and divide the rating by 50% to get a rough idea of its true capacity.

At that stage I had a 1KVA ups supported by a 3.5KVA generator. The generator certainly was a Chinese product, that's all I could get at the time. The symptoms you describe are spot on!!
Bugger....

[Justloadit]

Hi Clive,

Yes deep cycle batteries are available in the 7.2A size

[IanF]

Hi Clive,

Yes deep cycle batteries are available in the 7.2A size

Thanks for that I will bookmark as I am sure my alarms at work and home will need batteries shortly thanks to the power blackouts.

[Yahy]

Hello guys,
I am new to the forum. Since you guys are discussing inverters I wish dome one will be able to help me. At home I have a three phase electrical supply and wish to install an inverter to overcome the load shedding. I have two single phase 5KvA inverters with 24X12V (105 AH) batteries. Will it be possible to connect these to the three phase circuit. I only require to run phase A and phase B of the three phase setup. How do I do it.

Thank you
Yahya


Sent from my iPad using Tapatalk

[Justloadit]

It depends on what load you wish to run. If your loads are all single phase, but you have a 3 phase supply purely for load balancing, then you can use single phase inverters on each line you wish to back up.

The question is, what do you want to happen when there is a power failure?
Your reply will guide the answer.

[Yahy]

Thank you Justloadit for the prompt reply. My requirements are simple. When there is a power failure I want my the following to continue to work

1 the lights
2 the home alarm
3 the fridge (2)
4 the freezers (2)
5 the router
6 computers
7 the TV (2)
8 Electric kettle
9 2 x toasters

[HR Solutions]

I would suggest you read this thread from the beginning and you might find some answers

[Justloadit]

Running kettles and toasters on inverters is a no no.
Even a fridges and freezers on inverters is a no no.

The problem is that these devices are power hungry when it comes to stored power to do any work.

To boil water in a kettle requires approximately 1Kwat for about 10 minutes. This translates to 250watts of energy. If you have a 5Watt LED, it means that the 5 W LED would run for 50 hours on the energy it took to boil your kettle. See what I mean. Now lets look at what the battery has to do, if you take 1Kw or 1000watts at 12V, because that is where you start from, the battery has to supply 83 Amps for 15 minutes (1000w/12V = 83Amps) continuously. Even a 100Amp deep cycle battery will not survive this abuse. It is equivalent to cranking your car engine for 15 minutes non stop, would your car battery work after that time?

Large loads are best suited to a generator.

[Yahy]

Thank you justloadit I have taken note of your answer. Now that I have equipment what would you suggest

[AndyD]

I have discovered that re-charge time has now also become critical. That info sheet refers to between 6 and 12 hours, which is probably ok.

Battery charging against time on a graph isn't a flat line. Depending on the type of batteries and the type of charger it can take 30% of the battery charging time to complete the last 10% of the charging process. So, if you charge a battery for half the time that's stated for its full charge the chances are at least 75% of the charging process will already be complete.

I don't know what my UPS is supposed to be, but when we had occasional power-outs it allowed us more than enough time to safely shutdown our NAS (network attached storage) box and then it would happily keep our routers and access points going for about two hours.

Now, when the power goes off it does not hold the NAS box for even long enough for me to shut it down; I would say 3 minutes and it's dead. The unit is less than a year old so I assume the battery is ok.

Agree with previous comments, it's almost certainly batteries at their end of life. You can try putting the batteries on a charger like an 'optimate' which is touted as having a 'de-sulphating cycle', it might improve their performance.

Batteries are a major issue. Standard car type lead acid batteries aren't suitable for back-up solutions, if you're going to buy this type of battery for a UPS or inverter, yes it will be much cheaper that a deep cycle battery but you may as well just drop it straight in the dustbin when you get it home. Car batteries are designed to be discharged less than 10% during use, the deeper they get discharged the shorter their lifespan. An inverter or UPS is going to discharge its batteries at least to the 50% mark, some of the cheaper units will be even more harsh. I'd be surprised if car batteries last more than a couple of months under those conditions with the frequency of the power outages at the moment.

Battery chargers are equally critical to battery life as the battery itself. A good charger will go through at least 6 or 8 distinct stages of charging where the voltage and current is specifically taylored to the point the battery is at in the charging process (the charger I use in my workshop is a 16 stage). A half decent charger will have at least a 3 stage charging process followed by a trickle to maintain, this is the minimum I'd recommend for fairly good battery life. Cheap chargers are not adaptive to the state of charge of the battery, this type of charger will destroy a battery quickly. Unfortunately the poorer quality UPS's have cheap dumb-assed chargers as well as standard lead acid batteries which is the worst possible combination.