Summary of the entire post:
1. Buy a Pure Sine Wave UPS from a reputed local or Indian brand
2. Buy only new IPS battery of local brands like Hamko, Volvo, RahimAfrooz, Eastern, Saifpower etc (Never buy China ones)
3. Don't trust everything the seller says and don't buy a local IPS which has no brand (failure to locate the location and people manufacturing it or seller not disclosing this facts is what I meant)
4. Follow the UPS machine and battery manual and use it accordingly and do maintenance as recommended
I have been researching about home IPS/UPS for a very long time, watched a lot of videos on youtube, took personal review from real users also used IPS sellers and a few local IPS manufacturers. I will try by best to share the knowledge that I have gathered so far in short(These are my personal opinions and all information may not be true, also I will not give any reference and make this thread a lot longer)
Since all IPS nowadays have UPS mode I will commonly use the term UPS. Also, I have never seen any Square wave UPS so in that cases IPS term will be used.
What is IPS and what is UPS and what is this all IPS with UPS mode (or IPS cum UPS or Home UPS)?
IPS stands for Instant Power Supply, there is a delay of 1 second usually so everything will turn off and on (will restart) whenever power will go out but not restart again when power will be back
UPS stands for Uninterrupted Power Supply, the delay is usually 10-20 ms and nothing restarts, basically you may not even notice power going out or coming back again
IPS with UPS mode (or IPS cum UPS or Home UPS), these are now everywhere, they can function as both above either IPS or UPS
What should I consider before buying a UPS?
1. Your load requirement.
Multiply the watt you need with 1.45 to get the VA rating
Use this calculator here, it is not very accurate though but it is only I have come across during my research https://www.luminousindia.com/load-calculator
2. Output type: There are three types of output in inverters
a. Square wave: Old and totally obsolete almost nowadays. But almost all IPS that were used before 2012 were square wave ones, and even still the very cheap ones gives square wave output
b. Modified Sine Wave: This is just square wave with one or 2 extra steps to make it closer to sine wave. Many modern day UPS have this and also all those UPS for computers (except true online double conversion ones)
c. Pure sine wave: Almost all modern day UPS gives pure sine wave output. It is very close to the AC power we get from the grid.
Now time for comparison:
I will compare between square wave and pure sine wave, modified sine wave is better than square wave but worse than pure sine wave that you can say. so here we go
Pure sine wave UPS is same as grid power, so you will not feel any difference at all when power goes out and comes back on. Safe for any equipment.
Square wave output is not so bad, just there are a few downsides to consider -
1. AC motors (like fans) will make little noise
2. Speakers and microphones will make humming noise
3. Lifespan of equipment you will use with a square wave IPS will reduce a little (say 5-10%)
4. It will take 20-30% more power from grid to charge the batteries and also it is less efficient so you will get 20-30% less backup from them
5. You cannot totally use a few sensitive equipment like Microwave Oven and most laboratory (costly) equipment with this output (some will not work and some may even start fire)
Well, who has a laboratory with 10-500 lakh taka equipment at home or who is so rich enough (or let's just say wise enough) in our country that he will spend extra 70-100k more on a UPS just to run a Microwave oven during load shedding?
But, Modified sine wave and square wave inverters will be needing very little maintenance, will last two to four times longer than pure sine wave ones.
(If a pure sine wave UPS lasts 5 year, you can expect a Modified sine wave one to last 10-15 year)
Also, Modified sine wave and square wave inverters usually don't need servicing too often like pure wave ones (pure sine wave ones are likely to go faulty 2 to 3 times more likely than MSW ones, meaning if you visit a repair shop for a pure sine wave UPS once in three year then expect that you will be visiting a repair shop with MSW UPS or Square wave IPS, may be after 7 to 10 year or never)
Debunking some myths:
1. You cannot use computer without Pure Sine wave, NOT TRUE 100% false. Even lifespan of anything won't even reduce 1%. That's why all normal PC UPS gives modified sine wave output
2. Except pure sine wave, all your equipment will break down too soon. NOT TRUE. I said before they reduce lifespan of AC motors (almost negligible amount) only since they directly run off of the power output
3. Modified sine wave is nothing close to Pure Sine wave rather it can be called square wave as well
4. Turning off UPS mode will increase battery life span. NOT TRUE but increasing AC output voltage which some UPS has option for will and also turbo/fast charging the batteries will reduce lifespan
Now, in short anything that runs on DC power like PC, routers, ONU, LCD/LED Monitor and TVs will face no problem with square wave output, to be little safe modified sine wave is widely used nowadays
So far if you take a modified sine wave UPS or square wave IPS, you will hear little noise from your fans and speakers and that little extra energy cost, not that bad if you ask me.
The myths are mostly regarding these issues, so we are done here. Now moving on.
3. Battery:
You must buy a brand new local reputed brand IPS battery with official warranty for sure. Take Hamko, Volvo, Rahimafrooz, eastern, saif power but never Chinese ones
4. Charging Current:
Rule of thumb is that you will charge your lead acid batteries at 1/10th amp of their Ah rating.
Suppose, you have a 100 Ah battery so you will be charging it at 10 amp and 200 Ah battery at 20 amp but I have seen both local and branded RahimAfrooz ones to give 1/15th of the amp rating of their recommended battery. I have asked them, they all said that the batteries will last longer and it is just little slower than recommended not such a big deal. Some UPS has fast charging mode. I will talk about it in maintenance section
Point to be noted: UPS machine decides load and Battery decides backup duration
However, there are some restrictions though like you cannot use a 50 Ah Battery with 1000 VA UPS or two 200 Ah (total 400 Ah) batteries in parallel with a 1000 VA UPS. You seller will let you know the limits (even better if you talk to an expert about it say someone local manufacturer or those people who have been dealing with IPS/UPS repairing for a long time)
What must I avoid while buying a UPS?
1. Believe everything the seller says
2. Buying a used battery Never do it, I am saying again never ever do it
3. Buying used IPS/UPS without at least 3 month warranty
How do I calculate backup duration before buying UPS machine and batteries?
Batteries have 90-95% efficiency and UPS machines have 75-85%. So you will only get 70% of the power you are giving to the battery during backup (load shedding). Here is how you will calculate.
First calculate how much watt you have in battery store, well that's easy calculation: Volt X Ah rating (ex: a 12 Volt 200 Ah battery has 2400 watt)
Now since you will be getting only 70% of it. Now do this calculation: Watt storage in battery X 70% / you load in watt = Hour of backup
(ex. In a 12 volt 200 Ah battery, you have 2400 watt so 70% of it is 1680 watt, so if you put 500 watt load on it, you should expect little longer than 3 hour backup)
Ok, I am done buying, now what about maintenance so that my UPS and batteries last longer
1. Do NOT overload the UPS. If it rated for 600 watt, it is best you use it normally for up to 450 watt
2. Do NOT cover the Battery upside ( you must keep it open or in battery box, the boxes made for them are well ventilated). Also place the entire setup in an open well, ventilated area
3. Regularly check electrolyte level of battery and refill if needed (every 2-4 week is recommended)
4. Your battery will start heating up at the end of their lifespan (2-3 years). Replace them before total failure to avoid hazards like rarely they bloat and also damage the UPS machine and of course since they are producing heat, will take more power and increase your bill
5. Do not use high voltage mode or fast charging mode unless too much needed (High voltage mode is very rare in UPS so I will say about downside of fast charging, it will reduce lifespan of battery by a great margin say 50%. But you will be forced to use it in some rural areas where load shedding is too frequent and battery will not even get enough time to charge in normal mode)
6. While replacing the batteries at the end of their lifespan, you will get 20-35% discount if you exchange the old batteries.
Let's end with a story of myself
I used to use a Energex 1000 VA UPS since mid, 2019 and am extremely satisfied with it that I bought my father the same one just 2 months ago.
I need more backup now and replaced 200 Ah batteries with 2 piece 200 Ah one and started using them with the same 1000 VA UPS machine. The machine started making abnormal noise when I added the new batteries, which I informed Energex about and they did forbid me to use it with 400 Ah battery (2 200 Ah in parallel). Then the UPS machine malfunctioned.
Since I have 2 batteries, I bought a RahimAfrooz Powerpack 1600 VA 24 volt one. The seller and basically everyone said it will be best for me and also turns out it is true.
The performance of the powerpack UPS is more than satisfying, that I must admit. But, it gives modified sine wave output not pure sine wave, which has been bugging me for the last 3 months. So I talked to Energex again and told them to make me a Pure Sine Wave 1600 VA 24 Volt one and also wanted to know why everyone (with long time experience) is little negative about local pure sine wave UPS machines for long term usage?
His reply was like this, in our country Pure Sine Wave is not yet such improved (Except those RahimAfrooz ION Series) and people tend to use cheap Chinese parts to make them. So the Pure Sine wave one you are asking me to make for you will not last as long as that powerpack one you have now and using. The powerpack one will last more than 10 year and may be even 15 year without any issue but mine won't last that long and you may face a few issue with the Pure sine wave one but that is however too much rarely to happen like once in 6 months it will give trouble (ex. not auto start during load shedding sudden overload and shutdown, when there isn't actually a overload) which is very less likely to happen with the powerpack one and thats why RahimAfrooz for their sake of reputation doesn't make Pure Sine Wave cheap UPS machines like Luminous, Hamko and all other local brands. Their pure Sine wave UPS (ION series) comes in package and only the machine price is just almost three times more than luminous ones or any local ones.
Check here: https://estore.rahimafrooz.com/rahimafrooz-ips
Lastly, he told me. Before making your final order to make a PSW UPS, you must take time to decide if you are ok with your powerpack and its modified sine wave output and their downsides (mentioned above) and upsides (mentioned above) or want to really switch to pure sine wave one that you will be taking from me, I have honestly told you everything
Well, I ordered the Pure Sine Wave UPS just before this load shedding started. Since, I already took 2 UPS from energex and this is my third one, they gave hell of a discount. I think the person who makes them really likes me since I tend to understand a little bit more about electricity and these stuff. Alhamdullillah!!!
But, I will now however have to sell my powerpack UPS, it has 20 months warranty left and I have box, manual, warranty card, cash memo everything. I wanted to sell it for 13k (I bought it for 16.5 k) but yesterday I called 3 dealers of Rahimafrooz they won't even sell the new one for anything less than 22k (official price is 17.8k). Typical Bangalis, taking advantage of the crisis situation.
So, I guess I may even be able to sell the powerpack one with a little profit with luck (not that I want to, 14-15K is ok for me). If you want to buy that one, keep an eye out in bikroy.com, I will post the ad soon.