Air Conditionar on battery??

A

Alubukhara

Guest
Everybody knows you dont run heavy loads (Iron, AC etc) on batteries but
why?

A normal one ton Air Conditionar (AC) requires 1500 Watts so the current
(amps) required if the mains voltage is 220 should be 1500/220 = 6.8 Amp

A 100 Amp hour battery can provide 100 amperes for 1 hour right?

That means it should be able to run about 14 AC's (100/6.8) for one
hour??????????

I know its nonsense but what am I missing here?
 
"Alubukhara" <garma@sarda.com> wrote in message
news:gtomt9$d2k$1@news.motzarella.org...
Everybody knows you dont run heavy loads (Iron, AC etc) on batteries but
why?

A normal one ton Air Conditionar (AC) requires 1500 Watts so the current
(amps) required if the mains voltage is 220 should be 1500/220 = 6.8 Amp

A 100 Amp hour battery can provide 100 amperes for 1 hour right?

That means it should be able to run about 14 AC's (100/6.8) for one
hour??????????

I know its nonsense but what am I missing here?
Click to expand...



Several things

First it is recommended that you only discharge batteries down to 50% or
they pack up earlier.

So depending what voltage your battery is, is it 12 or 24 volt

Now these are simple calculations and I am not bringing any other factors in


If it is 12 volts and 100 amps, that is in watts (no extra losses taken into
consideration) 1,200 watts (12 volts x 100 amps = 1200 watts)



If it is 24 volt system it is 2,400 watts



Now if you only discharge the battery down to 50 % it equals 600 watts and
1200 watts.

Let us look at your air conditioning unit.

Using your numbers.


220 volts; 1500 watts and 6.8 amps


IE 1500 watts (220 volts X 6.8 AMP)

That would mean on a 12 volt battery that has a possible 600 watts of power,
it would run less than 1/3 of an hour (1500 watts into 600 watts)

On a 24 volt battery with 1200 watts the air conditioning unit would run for
say 3/4 of an hour (1500 watts into 1200 watts)

Of course this is with you using an inverter to convert the DC (Battery
Power) to 220 volts AC house power.

The inverter would not be 100% efficient, around 90% is the one I have, so
the actual running time would be less than the numbers I have shown.

Other numbers can be factored in but this is a very basic explanation of the
question you have asked.

On a practical note, running the battery flat to get more power out of it
you would find that the inverter would properly shut down on its low voltage
safety before you could get everything out of it.
 
"Jim Wilkins" <KB1DAL@gmail.com> wrote in message
news:be49eaa7-354a-4757-a806-b095b8ca4599@r34g2000vba.googlegroups.com...
On May 5, 3:38 am, "Alubukhara" <ga...@sarda.com> wrote:
Everybody knows you dont run heavy loads (Iron, AC etc) on batteries but
why?

A normal one ton Air Conditionar (AC) requires 1500 Watts so the current
(amps) required if the mains voltage is 220 should be 1500/220 = 6.8 Amp

A 100 Amp hour battery can provide 100 amperes for 1 hour right?

That means it should be able to run about 14 AC's (100/6.8) for one
hour??????????

I know its nonsense but what am I missing here?

You also need 220V from the batteries.
Click to expand...


The power supply for the A/C needs to be AC (Alternating Current) as from
an inverter.

220 volts DC will not run a normal everyday Air Conditioner.
 
Alubukhara wrote:

Everybody knows you dont run heavy loads (Iron, AC etc) on batteries but
why?

A normal one ton Air Conditionar (AC) requires 1500 Watts so the current
(amps) required if the mains voltage is 220 should be 1500/220 = 6.8 Amp

A 100 Amp hour battery can provide 100 amperes for 1 hour right?
Click to expand...
NO. High rate of discharge lowers the capacity and also reduces the battery
lifetime. It's complicated and varies between battery chemistries. You ned to
find the discharge rate at which the battery was rated.

Graham
 
On May 5, 3:38 am, "Alubukhara" <ga...@sarda.com> wrote:
Everybody knows you dont run heavy loads (Iron, AC etc) on batteries but
why?

A normal one ton Air Conditionar (AC) requires 1500 Watts so the current
(amps) required if the mains voltage is 220 should be 1500/220 =  6.8 Amp

A 100 Amp hour battery can provide 100 amperes for 1 hour right?

That means it should be able to run about 14 AC's  (100/6.8) for one
hour??????????

I know its nonsense but what am I missing here?
Click to expand...
You also need 220V from the batteries.

jsw
 
"Alubukhara" <garma@sarda.com> wrote in message
news:gtomt9$d2k$1@news.motzarella.org...
Everybody knows you dont run heavy loads (Iron, AC etc) on batteries but
why?

A normal one ton Air Conditionar (AC) requires 1500 Watts so the current
(amps) required if the mains voltage is 220 should be 1500/220 = 6.8 Amp

A 100 Amp hour battery can provide 100 amperes for 1 hour right?

That means it should be able to run about 14 AC's (100/6.8) for one
hour??????????

I know its nonsense but what am I missing here?
Click to expand...
Wrong calculation.

What was not addressed so far is that 6.8 amps at 220 V is "equivalent" to
125 A at 12 V. Iow, A = P / V.

So, you would need an even *bigger* battery than your already very very
large 100 A-hr battery.

And, a pretty expensive inverter. Altho an inverter providing 6.8 A at 220
may not seem like a big deal, the ability to handle much larger in-rush
currents upon start up *is* a big deal.

And these are paper calculations, as well. Everything gets worse off paper,
such as the voltage drop of batteries with discharge, IR drop, etc.

Now, if this were a car A/C, you proly would need *far less* than a ton of
A/C, AND you probably wouldn't need it to be on for a solid hour, so you
could make do with a smaller (separate) battery. But still a
battery-demanding proposition, which is why the battery should be separate
from the rest of the system, lest you become stranded.

If for an apt/ house, you'd proly need a pile of batteries -- but then,
you'd proly have the room for this.

Fortunately, the newer inverter technology for A/C (mini-splits or ductless)
seems to be pretty power-miserly, altho it is still a motor, but a much less
gluttonous motor.

EERs for minisplits can push 20+, so you get much more bang for your A/C
buck -- but a lot of bucks: these high-end A/Cs (fujitsu, mitsubishi) are
perty pricey.

Inverter mini-splits can have net *triple* the EER of an old clunker, in
particular old sleeve (thru the wall) units, which have notoriously low
EER's -- they claim 8, but proly pushing 6.

If you were actually considering trying this, I'd get the smallest units
possible in multiples, and "stage" them, to be kind to the batteries.
Inverter technology in newer A/Cs already has a kind of built-in staging,
but I'd still go with multiples of the smallest units -- which I think might
be 9,000 btu (3/4 ton), but poss. less.

Oh yeah, and *lots* of batteries. :)

--

Mr. PV'd

Mae West (yer fav Congressman) to the Gangster (yer fav Lobbyist):
Hey, Big Boy, is that a wad (of cash) in yer pocket, or are you just
glad to see me??
 
Alubukhara wrote:
Everybody knows you dont run heavy loads (Iron, AC etc) on batteries but
why?

A normal one ton Air Conditionar (AC) requires 1500 Watts so the current
(amps) required if the mains voltage is 220 should be 1500/220 = 6.8 Amp

A 100 Amp hour battery can provide 100 amperes for 1 hour right?

That means it should be able to run about 14 AC's (100/6.8) for one
hour??????????

I know its nonsense but what am I missing here?
Click to expand...

Amphours = Amps x Hours

Watts = Amps x Volts

Watthours = Amps x Volts x Hours

You left out "VOLTS" in your calculations

what is referred to in power consumption as "Watts" is actually
"Watthours".

Yukio YANO
 
One hour may be almost enough to lower the humidity 1% in a room or two.

"Alubukhara" <garma@sarda.com> wrote in message
news:gtomt9$d2k$1@news.motzarella.org...
Everybody knows you dont run heavy loads (Iron, AC etc) on batteries but
why?

A normal one ton Air Conditionar (AC) requires 1500 Watts so the current
(amps) required if the mains voltage is 220 should be 1500/220 = 6.8 Amp

A 100 Amp hour battery can provide 100 amperes for 1 hour right?

That means it should be able to run about 14 AC's (100/6.8) for one
hour??????????

I know its nonsense but what am I missing here?
Click to expand...
 
On Tue, 5 May 2009 12:38:24 +0500, "Alubukhara" <garma@sarda.com>
wrote:

Everybody knows you dont run heavy loads (Iron, AC etc) on batteries but
why?

A normal one ton Air Conditionar (AC) requires 1500 Watts so the current
(amps) required if the mains voltage is 220 should be 1500/220 = 6.8 Amp

A 100 Amp hour battery can provide 100 amperes for 1 hour right?

That means it should be able to run about 14 AC's (100/6.8) for one
hour??????????

I know its nonsense but what am I missing here?
Click to expand...
A 100 amp/hr battery isoften a 20 hour rating - i.e., 5 amps for 20
hours. That means that the battery can produce 60 watts (12volts x
5amps) for 20 hours. If an inverter is 80% efficient, the output
would be 48 watts at 220 volts.

For 1500 watts, you need 1500/48 = 31.25 times as much power input.
31.25 * 60 watts = 1875 watts into the inverter. 1875 watts at 12
volts is 1875/12 = 156.25 amps. This current level requires big
cables and very good connections - better to use a higher battery
voltage to reduce the current. At 24 volts the current would be 78
amps; at 48 volts the current would be 39 amps (this current level is
likely within the wiring abilities of most DIYers). Four 100 Amp/Hr
batteries wired in series for 48 volts might power that AC for half an
hour.

Serious battery power (as in solar and wind powered houses) uses
multiple large (200 Amp/hr or bigger) batteries to store power.
However, they are more likely to use DC powered devices than to waste
power generating AC via an inverter. (A 6 volt 200 Amp/hr battery can
be moved by two people, anything bigger usually requires a hoist or
forklift. Four of these in series make a 24 volt 200Amp/hr battery
bank.)

There are DC versions of almost every appliance - many designed to
work on a 32 volt marine power system.

I worked with a guy who got fed up with the continuous price hikes and
poor service from his local electric company (north Mississippi). He
set up a couple of Winchargers in the back yard and a battery bank
(surplus from the local telephone company) under the carport. As far
as I know, he used it for years until he moved back to South Carolina
to be near family. He was way ahead of the current green movement, as
he started doing this in the mid to late 70's.

John
 
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