12v- 240v inverters?

Using a decent size battery, what could you run with a set up of this nature, and how long before having to recharge? I know its a bit of a" how long is a bit of string" type question, but a general overall idea would do.

Thanks Axle.
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Reply By: Lex M - Tuesday, Jan 06, 2009 at 18:32

Tuesday, Jan 06, 2009 at 18:32
Rough (very) rule of thumb.

Amphour capacity of battery X 12 gives watthour capacity of battery.

Divide this by wattage or VA rating of 240v device and gives running time in hours.

This disregards inefficiency of inverter and other losses, assumes the wattage/VA rating of the 240v device is accurate and assumes your going to destroy the battery by totally flattening it.

Half that time would be closer.

I reckon the length of the piece of string is about twice the length from the middle to one end.
AnswerID: 342899

Follow Up By: Member - Axle - Tuesday, Jan 06, 2009 at 19:16

Tuesday, Jan 06, 2009 at 19:16
Thanks Lex, will take note of those figues.

Cheers Axle.
FollowupID: 610627

Reply By: Peter_n_Margaret - Tuesday, Jan 06, 2009 at 18:53

Tuesday, Jan 06, 2009 at 18:53
Give us a clue Axle, what do you want to run?

A big winch draws maybe 500A @ 12V, that is 6000W, that is more than double what you can get out of 240V/10A power point, but you need a very big inverter, and you won't run it for long.

OKA196 Motorhome
AnswerID: 342903

Follow Up By: Member - Axle - Tuesday, Jan 06, 2009 at 19:30

Tuesday, Jan 06, 2009 at 19:30
Hi Peter, Nothing like that mate !,( Idon't think!..lol) Just usual lights , fridge, camping whatever.

Its a 1000W inverter, a hand me down from a relo, who knows about as much as i do on these things. (zilch).

I'm trying to do what the daughter says," Get in the modern world dad".!!.

Cheers Axle.

FollowupID: 610630

Reply By: stefan & 12 times Dakar winner - Tuesday, Jan 06, 2009 at 19:11

Tuesday, Jan 06, 2009 at 19:11
Myself and Sister both run 40lt 240v fridges off an inverter in our cars
AnswerID: 342906

Reply By: Member - Kiwi Kia - Tuesday, Jan 06, 2009 at 19:20

Tuesday, Jan 06, 2009 at 19:20
Remember that the inverter will shut itself down when the voltage drops below (aprox) 11.5 volts.

AnswerID: 342908

Follow Up By: Member - Axle - Tuesday, Jan 06, 2009 at 19:36

Tuesday, Jan 06, 2009 at 19:36
G/day Kiwi Kia

So you would have to have continuous charge??

Your talking to a electrical nightmare here!...lol.

Cheers Axle.
FollowupID: 610633

Follow Up By: Member - Kiwi Kia - Tuesday, Jan 06, 2009 at 19:51

Tuesday, Jan 06, 2009 at 19:51
Hi Axle, No, I was just pointing out that the inverter will not run the battery all the way down to an effective zero charge.

I think that you will find that most inverters have auto low voltage cut-out's, some may be set a bit higher then others. This can be useful in preventing you from discharging your battery to a point that may shorten the battery's life. If you want to know what sort of ampere hours you can get from your battery try the following experiment;
Connect up your 12 / 230 volt inverter.
Plug in an electric clock and a known wattage lamp.
Set the clock to 12 o'clock.
Switch on
When the voltage drops to the auto cut-out point the output 230 volts will cease, the clock will stop and the light will go off. The time on the clock will tell you how long the 230 volts was supplied to your lamp. You now know how many watts were consumed and for how long. If you read the label on the inverter you will see how efficient it is and what power is actually consumed in the inverter. You now have all the info to work out what amp / hours you can safely draw from your battery.

FollowupID: 610637

Follow Up By: Member - Axle - Tuesday, Jan 06, 2009 at 21:01

Tuesday, Jan 06, 2009 at 21:01
Thanks for that!.

FollowupID: 610656

Reply By: _gmd_pps - Tuesday, Jan 06, 2009 at 19:59

Tuesday, Jan 06, 2009 at 19:59
What is a "decent size" battery ? That depends on what you want to do.
I have a 1800W Pure Sine wave Xantrex Inverter.
Max input is 175Amp .. it is hardwired and has a automatic transfer switch for the outside 240V.

I have 2 Xantrex LM500 Battery monitors on each bank of 4 6V 220AH which gives me a total capacity of 840AH. I use two separate banks and can charge both independently.

My rule is not to discharge the batteries below 60% (55 at most).
Generally our normal consumption without charging brings one bank down to 75%-70%. So we have 2 days without charge and without compromising our consumption. This was true without the solar panels. On a good day I charge one bank back to full within 7-8 hours.

Here some consumption figures from the battery monitors.

Espresso machine heating 95 Amp
2-3 times a day for 5 minutes

Espresso machine heating/pumping 115 Amp
4-6 times a day for 1 minute

Microwave 800W on high 90 Amp
rarely use it when not on 240V

Desktop PC (2 hard drives 4G Ram) 6 Amp
including Maxon Router and wireless
access point
2-4 hours a day depending what we do

24" LCD Monitor 6 Amp
30" LCD Monitor 7.5 Amp
2-4 hours (sometimes only one display)

Sony 5.1 channel stereo 4 Amp

Satellite receiver 3 Amp

Fridge 120L Vitrifrigo with external compr 4.5 Amp

Freezer 35L Waeco 3.5 Amp

running time of fridge and freezer obviously depends
on temp and how often you open and contents.
Freezer will run fairly often - I calculate 50% of the time
for the fridge I calculate 30%. The Vitrifrigo is quite efficient.
It needs a bit more current (larger compressor) but does not
come on as often as the Waeco on fridge setting.

Small Toaster 80 Amp
rarely use it when off 240V

Waterpump 11l/h 6 Amp
20 minutes a day in total is plenty

The fridge and the freezer are connected to 12v directly or course not over the inverter but of course they are part of the energy balance.

The inverter itself needs 1.5 Amp on idle when not on power save. In power save it needs less but I only switch it on when I really need the 240V.

My large Laptop with AC adapter needs 6 Amps and we
also use it 2-4 hours a day (its a 17" 1920x1200 screen)

Then there is a heap of small gadgets like AA battery charger, mobile phone charger, USB hubs etc.

One concern in configuring such a system is weight. Each of the batteries weigh 30kg so this is a total of 240kg on batteries.
This is where you should start when you have limited loading capacity.

good luck

AnswerID: 342915

Reply By: dedabato (SA) - Tuesday, Jan 06, 2009 at 20:04

Tuesday, Jan 06, 2009 at 20:04
Below is the Appliance Estimated Watts Recommended for using an choosing Inverter....

Blender 300W 600W Power Inverter
Blow Dryer 900-1500W 1800W Power Inverter
Cappuccino Maker 1250W 1200W Power Inverter
CD or DVD Player 35W 120W Power Inverter
Clock Radio 50W 120W Power Inverter
Coffee Grinder 100W 120W Power Inverter
Coffee Pot (4 Cup) 650W 1200W Power Inverter
Coffee Pot (10 Cup) 1200W 1200W Power Inverter
Computer - Laptop 50-100W 120W Power Inverter
Computer - PC & Monitor 200-400W 600W Power Inverter
Computer - Printer (inkjet) 60-75W 120W Power Inverter
CPAP Breathing Machine 200W 300W Power Inverter
Fan - 12" 3 speed 230W 300W Power Inverter
Fan - Table 25W 120W Power Inverter
Freezer 500-800W 1200W Power Inverter
Frying Pan 1200W 1200W Power Inverter
Game Console 100-300W 600W Power Inverter
*Heater (1/3hp) 1200W 1200W Power Inverter
Hot Plate 1200W 1200W Power Inverter
Iron 1200W 1200W Power Inverter
Lights - 100W Incandescent 100W 120W Power Inverter
Lights - 100W Compact Fluroescent 30W 120W Power Inverter
Microwave - 600-1000W Cooking Power 1100-2000W 2400W Power Inverter
Mini Christmas Lights 25W 120W Power Inverter
Mobile Phone Charger 25W 120W Power Inverter
MP3 Player Charger 120W 300W Power Inverter
Refridgerator/Freezer 600W 1200W Power Inverter
Satellite Dish 30+W 120W Power Inverter
Stereo 30-100W 120W Power Inverter
Toaster 800-1500W 1800W Power Inverter
Toaster Oven 1200W 1800W Power Inverter
TV - 25" Colour 300W 600W Power Inverter
TV - 19" Colour TV or monitor 160W 300W Power Inverter
TV - Black & White 30W 120W Power Inverter
TV - 13" Colour TV/VCR 230W 300W Power Inverter
VCR 40-60W 120W Power Inverter
Vacuum Cleaner 300-1100W 1200W Power Inverter
Waffle Maker 1200W 1200W Power Inverter
Washing Machine 920W 1200W Power Inverter
*Air Compressor - 1hp 2000W 2400W Power Inverter
*Airless Sprayer - 1/2hp 600W 1200W Power Inverter
Band Saw 1200W 1800W Power Inverter
Circular Saw - 6 1/2" 1000W 1200W Power Inverter
Circular Saw - 7 1/4" 1200+W 1800W Power Inverter
Circular Saw - 8 1/4" 1800W 2400W Power Inverter
Chop Saw 1550W 2400W Power Inverter
Cut Off Saw 1000W 1200W Power Inverter
Disc Sander 1200W 1800W Power Inverter
Drill - 1/4" 250W 300W Power Inverter
Drill - 3/8" 500W 600W Power Inverter
Drill - 1/2" 750W 1200W Power Inverter
*Electric Chain Saw - 14" 1200W 1800W Power Inverter
*Grinder - Portable 1380W 1800W Power Inverter
Jig Saw 300W 600W Power Inverter
Table Saw 1800W 2400W Power Inverter

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AnswerID: 342918

Follow Up By: Member - Axle - Tuesday, Jan 06, 2009 at 21:54

Tuesday, Jan 06, 2009 at 21:54
" Bloody Hell ", "Cop that young Harry"!!....lol.

Cheers Axle.
FollowupID: 610675

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