Battery Voltage Determination

Why is it obvious that your mains supply is 230Vac?

The battery voltage should be that for which the inverter was designed.

The battery voltage must be compatible with the manufacturer's specified input voltage range, as listed on the data sheet for the inverter.

It is very obvious that you know very little about electricity, chemistry, physics, and the meaning of units.

The voltage produced by a battery is established by the chemistry of the reagents in the battery. The power density, recharge efficiency (if possible), discharge rate, shelf life and total energy stored in the battery will be mostly determined by the dimensional construction of the battery.

The electrical engineer designing any system that uses a battery will therefore only have certain sizes and values of batteries to choose from for their design. So less than optimum conditions will be normal.

Since you do not understand how to quantify your electric load in measurable units nor how long you intend to use this pack up power, I recommend that you hire a local electrician/engineer to guide your purchase.

You need help! You might even want to consider taking a course in electricity. Not electronics.

My guess is that the equipment you mention runs on voltages from 5Vdc to 230Vac.

Once again, you are in over your head. Get some local help.

"Similarly, for Forklifts i have seen most of them using 48Vdc battery , why 48Vdc, , how do i decide that?"

$$$ Cost $$$ The higher the voltage they can make it the less the current draw then a lower voltage battery to do the same amount of work. Which allows use of electrical devices rated for lower currents. Which drop the cost to build the fork lift.

There is little difference in cost between a 48 volt and lesser voltage battery that will do the same amount work. The lesser voltage battery will need to compensate by having a higher AH rating. Making it about equal in size.

Every one of those fork lifts come off the production floor with name plate listing the battery voltage and recommended AH rating. So does you inverter!

I m using an inverter

The required battery voltage is literally marked on your inverter or at the very least in the inverter data sheet or operating manual. Standard inverter input voltages are almost always 12VDC until you get up to the larger sizes where the current becomes too large at 12VDC so 24VDC and 48VDC are required (review ohms law for more information).

This is probably going to confuse you even more, but if you are using a cheap square wave inverter instead of a true sine wave inverter you may blow up your inverter (and possibly damage your computer and TV) if you try and connect it up to the tube light or possibly computer and TV.

These loads don't like 230V AC square waves (again this should be indicated in your inverter manual)

Read the manual before connecting up the inverter. If the inverter is a square wave type put it back in its packaging unused and return it for a refund.

I'd guess you'll need 3 12v car batteries for EVERY hour you run all that stuff. As said elsewhere, a cheap inverter will possibly fry your computers, fan and fluorescent lite. Tell us EXACTLY what you're doing, the information on the specifications plates of the computers, fan, and tube light. Specifically, how many watts does each use? How long does the electricity stay off? Do you need both computers? Is one a laptop? Get some white 12v LED lites, a 12v 4" cooling fan, and use the laptop on battery. No need for an inverter, and one battery should last four hours.

You have to understand that your loads (computer,TV,..etc) in the room are AC loads (230Vac).and your inverter converts the D.C current of the inverter,s battery to A.C current and step up the voltage of the battery to 230Vac. no battery can supply A.C current or A.C voltage .all kinds of batteries are D.C voltage suppliers

It depends on the Inverter you are using and the backup time you need.

It may be from 6V to 12V normally UPSs found for such purpose in market.

Higher voltage is preferred to have smaller conductors and low current switching hardware.

The individual battery voltage level selection depends on how much room you have to work with, where you are putting/locating the battery, what the rated operating voltage of all devices being attached to the system.

Most heavy duty batteries used throughout industry are either "single-cell" units or an enclosed unit made up of the proper number of individual cells to required to produce the needed voltage level.

Most 48 volt forklift batteries are actually an encased unit consisting of 22 individual cells.

Your equipment requires AC to operate whereas a forklift operates as a DC system and it is extremely different than an inverter or other UPS system.

2.15 to 2.33 Volts per cell is the nominal voltage for lead acid batteries with similar but different voltage levels for other types of batteries such as Lithium Ion, Alkyline, etc.

For instance using a lead acid battery wet configuration:

If you need 120 Volts to supply your application it would require 50 individual 2.25 volt cells to attain the minimum acceptable voltage level of 117.50 volts and in order to get the voltage level to be at 120 volts, you would need 53 individual 2.25 volt cells.

Or; You could use 10 each 12 volt rated, encased batteries.

If you chose 48 Volt batteries; 2 each would supply 96 volts which is not enough voltage and 3 each would supply 144 volts which would be too much and cause severe equipment damage.

You must consider the amount of electrical current being consumed by your attached devices (load).

The higher the current demand (load), the larger physical size of battery and the more room you would need to stage the battery rack.

You must know the operating voltage of all devices being attached to the system.

You must take into consideration where the batteries will be physically located as lead acid batteries produce free hydrogen and present severe explosion risks as well as a highly corrosive atmosphere that will damage pretty much any and every thing in the immediate vicinity.

If using wet cell lead acid batteries you must provide the capability to "equalize" battery cells at a voltage higher than 120 volts as specified by the battery manufacturer or else suffer premature battery failure due to sulfation of the plates.

In order to protect your sensitive equipment on the load side of the inverter you will need to install a 1:1 transformer of the correct size along with a good noise filter. (LC Network)

As you can see there are many things to consider when selecting and designing a battery system.

It is great that you are trying to learn and even more encouraging that there are still young ones with the curiousity and initiative to experiment.

By all means keep searching and asking questions when you reach an impasse or need answers but be sure to proceed with caution and stay safe.

"Your equipment requires AC to operate"

Are you sure about this statement↑?

Not really Lyn.

The OP did state 230 VAC and I have not encountered very many personal rooms that have a fan, computer, tube light, and TV that all operate on DC input.

I am not sure that he/she has a full grasp on anything at this point.

I am hoping that they read all of and understand the response comments well enough to realize there is more to consider than just the voltage level of the selected battery.

And I am hoping we do not "squash" their desire for seeking knowledge but at the same time give them enough information to keep from making a costly and/or life threatening decision.

It is not clear whether you want a battery for your inverter or the other equipment. If the fan runs on 12VDC, then you need a 12V battery for it. If the forklift has a 48V motor, then it needs a 48V battery.

The choice of BATTERY VOLTAGE will be dependent on THE TOTAL LOAD (watts) consumed by all your electrical equipments.

Assuming the total load taken by your equipment is 240Watts.

Assume you wish to use 12V DC to power your inverter.

DC Current =240/12=20Amps

If you use 24V Battery , your DC Current=240/24=10Amps

On the other hand if you wish to use 48V Battery, your DC Current =240/48=5Amps

Thus your choice of the Battery Voltage will be dependent on the total load consumed by your domestic appliances.

The total load will determine DC cable size that will power your INVERTER(S).

The bigger your DC Current, the bigger will be your CABLE SIZE and consequently the higher cost of installation. By choosing higher values of Battery voltage, you reduce your DC current and this also reduces the cable size and consequently your cost of installation.

I hope this explanation is well understood.

Why are you talking to me? Talk to the OP. He's the one with the questions.

The only thing you have to consider is what voltage the inverter has been designed for & the capacity of the battery. The voltage will be listed in the inverter specifications

To decide on the capacity of the battery needed, work out what the total load of all appliances that you want to run from the inverter & then decide on how long you want it all to operate for & then do the calculations to work out the total capacity needed to do the job.

I'm sure if you have this information & come back & ask some of our very intelligent members what they would recommend they would help you do the calculations to determine the best capacity battery to do your job

google it out

• usually SUM(of "labelled" power draw) should be 30% of that of what is on a label of the inverter e.g. -- say 2xPC + FLB + Fan + TV = (2 x 240 + 20 + 20 + 120) x 1W = .64 kW(kilo-watts) requires .64kW / 30% = 2.1kW /!\ inverter incase you don't want to cold start the high consumption devices you /!\might manage with 1kW 1
  
• 48V battery is 40 x 1.2V Li-ion or Ca-Ni or Ni-MH or PbSO cells in series it reduces the "short circuit" current what may be fatal due electo-chemical over heating -- there may be some other trick for it