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yudhi
07-14-2008, 07:11 AM
Hello All.

I'm new here.
I need help to calculate battery capacity for UPS I planned.
I want to buy a Inverter with UPS mode.

The inverter have :
- 24VDC Input
- 220VAC 3000Watt Output
- Eficiency 90%

I need to have 6 or 12 hours backup time at Full Load (3000Watt).
So how many AH (amps hours) I should prepare and how to calculate that ?
What I know is I need to make 2 x 12V battery in serial to get 24V.

Many thanks.

JohnS
07-14-2008, 07:35 AM
Hello All.

I'm new here.
I need help to calculate battery capacity for UPS I planned.
I want to buy a Inverter with UPS mode.

The inverter have :
- 24VDC Input
- 220VAC 3000Watt Output
- Eficiency 90%

I need to have 6 or 12 hours backup time at Full Load (3000Watt).
So how many AH (amps hours) I should prepare and how to calculate that ?
What I know is I need to make 2 x 12V battery in serial to get 24V.

Many thanks.

You are going to need an enormous battery. For 3 kW out and 90% efficiency, you need 3333 W in. At 24 V dc, that's 139 A. For 6 h, that's 834 Ah, for 12 h, 1668 Ah.

That is what you need to draw, not the battery's rating. Even a deep discharge type battery should never be discharged to less than 20% of capacity, and 50% will result in much longer life. (Divide above by 0.8 or 0.5)

Discharged to 20%: 1050 Ah for 6 h, 2100 Ah for 12 h
To 50%: 1700 Ah for 6 hr, 3400 Ah for 12 h.

Those are huge batteries and you may wish to consider a much smaller UPS battery supplemented by a generator.

yudhi
07-14-2008, 07:47 AM
You are going to need an enormous battery. For 3 kW out and 90% efficiency, you need 3333 W in. At 24 V dc, that's 139 A. For 6 h, that's 834 Ah, for 12 h, 1668 Ah.

That is what you need to draw, not the battery's rating. Even a deep discharge type battery should never be discharged to less than 20% of capacity, and 50% will result in much longer life. (Divide above by 0.8 or 0.5)

Discharged to 20%: 1050 Ah for 6 h, 2100 Ah for 12 h
To 50%: 1700 Ah for 6 hr, 3400 Ah for 12 h.

Those are huge batteries and you may wish to consider a much smaller UPS battery supplemented by a generator.

Wow....I need huge capacity :D

Generator is my last option....smoke, noisy and the fuel price is rising and never stop :p

Do you ever know how much is battery which have huge capacity which is used by most cellular provider at their BTS ?
I saw battery with capacity over than 2000AH.

Thanks.

JohnS
07-14-2008, 08:36 AM
Do you ever know how much is battery which have huge capacity which is used by most cellular provider at their BTS ?
I saw battery with capacity over than 2000AH.

Thanks.

I don't know. Among people who live "off grid" and use solar or wind power, batteries rated for golf carts, generally 6V, 400 Ah, are popular and relatively economical. They wire four in series for 24 V, and either operate several separate banks or parallel them for more capacity (when paralleling batteries, there may be some problems getting all of them to charge/discharge uniformly, small differences in cell voltage can be a problem).

yudhi
07-14-2008, 08:41 AM
Thanks a lot....its very helpful for me.

kiran.elcom@gmail.com
04-12-2009, 01:50 AM
My load is 3KW & I want to take inverter. How I shuld decide battery capacity Pl. tell what should be battery capacity

MJWorner
04-13-2009, 05:51 AM
I don't know. Among people who live "off grid" and use solar or wind power, batteries rated for golf carts, generally 6V, 400 Ah, are popular and relatively economical. They wire four in series for 24 V, and either operate several separate banks or parallel them for more capacity (when paralleling batteries, there may be some problems getting all of them to charge/discharge uniformly, small differences in cell voltage can be a problem).

This scenario calls for 20 batteries at 100% discharge (B A D bad) or 40 batteries at 50% discharge (I would not go below that point, and not often) which makes containment, ventilation (explosion proof!) and heat dissipation into real live issues. Plus, as John says all batteries must be the same type, size and age or they will start discharging each other.

Wiring would be ten parallel banks of four batteries in series. Charging with positive at first bank and negative at last bank is proper way to keep everything equalized.

Major dollars here for a constantly deteriorating asset. Buy a lot of gas for that money, and it will be fresh with every fill up...

Unregistered
06-11-2009, 04:58 AM
My load is 3KW & I want to take inverter. How I shuld decide battery capacity Pl. tell what should be battery capacity

*rolls eyes*
Some simple maths:
V A R & W A V and for the yanks E I R & P I E same **** just using the equality values but im going to explain in base value.

Meanings: V=Volts A=Ampere R=Ohm's W=Watts

Ohms law (1) Requires to part of the calculation so any one is able to do this all you need is a multimetre to start.

Calculate:
Volts: V= AxR
Amps: A= V/R
Ohms: R= V/A

Working with watts:
Watts: W= AxV
Amps: A= WxV
Volts: V= W/A

Want an AH:
Say with a single filament 24W at a 12V supply what AH do i need to run it for lets say 24hrs?

Here now to put the above info into play:
We need the amps that is being drawn from the 24W filament so:
A=24/12 (2AMP)

So! 2A * 24HR = 48AH one thing to mention this is not for a deep charge battery! else add 20% to 48AH as we do not like to drain a deep plate as it f's it!

I can't be stuffed typin anymore lol have fun with the new info

krishne
07-10-2009, 11:14 PM
i want to run one sheeling fan and two tupe lights with 12 hours backup.so which battery is suitable for it and how make this calculation.thanking you

Yves
08-10-2010, 08:40 PM
Hi,

I need help to calculate the total Heat Dissipation for a 20kva UPS.

Many thanks.

Unregistered
08-26-2010, 05:06 AM
how to confirm the battery voltage?
i mean whether to go for 12V battery or 2V battery to suppliment 1200AH.

bns
08-26-2010, 05:16 AM
You are going to need an enormous battery. For 3 kW out and 90% efficiency, you need 3333 W in. At 24 V dc, that's 139 A. For 6 h, that's 834 Ah, for 12 h, 1668 Ah.

That is what you need to draw, not the battery's rating. Even a deep discharge type battery should never be discharged to less than 20% of capacity, and 50% will result in much longer life. (Divide above by 0.8 or 0.5)

Discharged to 20%: 1050 Ah for 6 h, 2100 Ah for 12 h
To 50%: 1700 Ah for 6 hr, 3400 Ah for 12 h.

Those are huge batteries and you may wish to consider a much smaller UPS battery supplemented by a generator.

DEar Johns,

How to be sure about battery voltage? whether to go for 12V battery or 2V battries.

JohnS
08-26-2010, 09:39 AM
DEar Johns,

How to be sure about battery voltage? whether to go for 12V battery or 2V battries.

The calculation was done for 24 V.

If 12 V batteries are used, 2 of the capacity must be wired in series. If individual cells (2V) are used, 12 of that capacity must be wired in series.

zaheer708
05-01-2011, 01:44 AM
Greetings every body.

I have total connected load = 1000VA

UPS Rating = 1200 Watts

Battery Rating = 1300 Ampere Hours

Voltage = 240 V

For how long will battery supply power to load? I mean the battery run time.

Thank you very much

JohnS
05-01-2011, 04:23 AM
Greetings every body.

I have total connected load = 1000VA

UPS Rating = 1200 Watts

Battery Rating = 1300 Ampere Hours

Voltage = 240 V

For how long will battery supply power to load? I mean the battery run time.

Thank you very much

Theoretical, at 100% efficiency
1300 Ah x 240 V /1000 VA = 312 h.
Reality will be less. Battery banks should never be fully discharged as it shortens life. Estimating 50 %, maybe 150 h.

Unregistered
07-21-2011, 12:24 AM
Dear All,

Here is the formula to calculte battery size accroding to your load.

1-Calculte load current in Amp (Total power/UPS battery operting voltage)
3-Battery charger capacity=Battery size*0.1=XXAmp

Unregistered
08-10-2011, 02:07 PM
I am trying to determine the amount of time my UPS will run with the current batteries we have.

We have 109.6 ah batteries, two strings of 24 jars series together for a link voltage of 324 VDC and the two strings are in parallel.

We have a 24 KVA UPS, but only have 30 amps of load on the UPS, (3 phase, 30 amps phase A, 17 amps phase B and 18 amps phase C).

I need to find out how long our load will stay supported on these batteries before they shutdown due to the DCUV point of the system which is 1.75 vpc.

I would like to know the time for the current load and how long it would last at full load.

pwr4youflorida@gmail.com

JohnS
08-10-2011, 05:29 PM
I am trying to determine the amount of time my UPS will run with the current batteries we have.

We have 109.6 ah batteries, two strings of 24 jars series together for a link voltage of 324 VDC and the two strings are in parallel.

We have a 24 KVA UPS, but only have 30 amps of load on the UPS, (3 phase, 30 amps phase A, 17 amps phase B and 18 amps phase C).

I need to find out how long our load will stay supported on these batteries before they shutdown due to the DCUV point of the system which is 1.75 vpc.

I would like to know the time for the current load and how long it would last at full load.

pwr4youflorida@gmail.com

We need to know the output voltage of the UPS (and is it measured line-to-line or line-to-neutral).

Unregistered
05-26-2012, 09:49 AM
i want to calculate the heat dissipated by the VRLA batteries..how should i calculate that..
can i use de formula Q=mCpdt..if yes how should i use it..Plz reply asap..or mail me on jain.nikunj17@gmail.com

Unregistered
09-24-2012, 11:34 PM
hai, i decided to buy a 600va ups for home , can u plz tell me how much AH battery required to run the show for 6 hours. plz advice me about tubular battery also.

many thanks.

vinodh.

JohnS
09-25-2012, 04:38 AM
hai, i decided to buy a 600va ups for home , can u plz tell me how much AH battery required to run the show for 6 hours. plz advice me about tubular battery also.

many thanks.

vinodh.

You need 3600 Wh of output. If we assume 75% efficiency, you need 4800 Wh at the battery. At 12 V, that is 400 Ah of battery. If you are not at full load, less battery would be needed, so you should look at actual power your load draws.

Unregistered
01-17-2013, 08:14 PM
Hello Sir,

I have 30amp,415v supply machine.Please tell me how many kva ratings ups require.

Unregistered
10-24-2013, 12:19 PM
1. Establezca la temperatura máxima a la que se puede enfriar 1000 Kg. De agua
a 90°C, empleando 1000 Kg. de amoniaco que entra a -40°C y sale a 15 °C
siendo su calor especifico Cp de 0.520.