Inverters (and yes, I've performed a search)

08 83498332 = Pecan Engineering....

They manufacture and supply solar panels and invertors.
Ask for Bruce... Between 9am & 3pm...*************************************
Just countin the days till July 5th. *Cape York Trip*
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I have used lots of inverters but always cheap ones. I found they all draw current even when there is no load and the bigger the rating the more waste there is. They all drained the battery if left conected, even if not powering anything.

I have about 5 or 6 of the things and never use them for camping/touring. I have found the Piranhas the best by far. Why do you want one may I ask.

Sean

Most inverters are not 100% efficient. They have a baseline current draw, and are only about 70-80% efficient at the "real" conversion of the rest of the power from 12 volts dc to 240 volts ac. Count on an efficiency of 70% and you shouldn't go too far wrong ie. 70 watts (small TV) will draw about 100 wats from your inverter (12 volts x 8.3 amps) , which will need 120-140 wats (12volts x 10-12 amps x 1 hour) to recharge your battery.

If you must have it get as much "native" 12 volt gear as you can as it saves the capacity in you batteries. It must be said that inverters make good heaters on those cold and frosty nights ;-)

Rohan, I echo sean's question - why do you want one?? With excellent 12 volt lights available, 12volt or gas fridges, gas heating, gas cooking I can't see any reason for using such an inefficient energy source. Maybe you have thought of something that I haven't but I charge my mobile phone and video camera, run my PC and GPS, light my camp, cook my meals and refrigerate my food and drink without 240volts! Cheers!

Rohan, I echo sean's question - why do you want one?? With excellent 12 volt lights available, 12volt or gas fridges, gas heating, gas cooking I can't see any reason for using such an inefficient energy source. Maybe you have thought of something that I haven't but I charge my mobile phone and video camera, run my PC and GPS, light my camp, cook my meals and refrigerate my food and drink without 240volts! Cheers!

Just to confirm that inverters draw power while attached and turned on - not turned off, but you know your power point at home draws current when the telly is turned off, just an electricity thing. As for your conversions you only need to use ohm's law and not get confused by the wrong question, it is not comparing watts but comparing watts to volts. If it is a 240 volt appliacnce then you it will take out of an inverter X amps at the watts rating divided by its volts rating - 240 of course or you would not be using an inverter. Therefore, a 100 watt appliance reliant on a 240v power source will require current at A = W/V which would be 100 watts divided by 240v = 0.41amps. The conversion of 12v pulse to a 240v wave is a separate matter governed by the efficiency of the inverter. That uses current itself as people have pointed out, the higher the 240v current is required the less the efficiency of all inverters and current consumption rises. that's where quality of pure sine wave and modified sine wave inverters and respective build qualitites come into play.

So use an inverter with a power (watts) rating greater than your applicance, but to measure current draw you then forget about the inverter rating (like an accelerator, only as much current is drawn thru the inverter as is want to be consumed by the appliance) and measure the watts against the voltage source it is operating off.

Watts don't get pumped into batteries, except as a function of current, so it goes round. I run my inverters off stationary batteries not even in the car - i just recharge them the next day, so yes you can run an inverter off a wagon 12v socket without the vehicle running. As with any applicant, 12v or 240v off an inverter, you should be conscious of running your battery out of amps (which you can measure by the state of the voltage).

An inverter cannot be hooked up to an alternator because alternators themselves put out unregulated current and pretty uneven voltage levels, governed primarily by the person operating the throttle. Every decent inverter has a fuse say 20 amps, my alternator pumps out at mid throttle about 90amps, 90 into 20 means blown fuse and inverter not operating.

I think everything i have said it right and trust someone will correct me if i have slipped up.

Voltage = watts / amps
Amps = Watts/ votlage
Watts - Voltage multiplied by Amps

Inverters are great, just use them when you need them and disconnect the when you don't, or monitor your batteries and recharge as soon as possible.

Power (watts) = Voltage (volts) times Current (amps).
Power out = Power in times efficiency.
So if a 100 watt appliance is connected to the inverter, the current draw at 12 volts (input to the inverter) is given by (100/12)/0.8 amps (10.4)assuming an 80% efficient inverter.
Relatively cheap inverters are available from Jaycar Electronics with efficiencies of around 90%. It is a lot safer if these are installed with a switch in the input side (12v) and hence the problem of idle current flattening the battery is avoided. They can be connected straight into the vehicles electrical system without much trouble. I use one for charging video camera batteries, digital camera batteries and running and charging laptop battery with no problems. It beats purchasing and carrying around the extra charger for each device to connevt to the 12v car supply.

To Gary in Oz, in retrospect i should not have attempted to answer a technical question late at night after a bottle of red wine, apologies and am glad to be corrected, of course a battery only takes from an alternator what its internal resistance permits - but the question was "can i connect my inverter directly to my alternator" not "to my battery which is charged by my alternator" - so i would like to see what an alternator would do connected directly to an inverter which has no internal resistance other than a relatively small fuse.

And yes an inverter can, and it is better for the battery if the, be connected to the battery while the alternator is charging it.

Cheers all.

Thanks for all the advice folks. I've picked myself up a small 140W unit from Jaycar. I've tested it out on the biggest current drawing appliance it will be used on - the PC battery charger, and it works fine. I didn't measure the current drop but it took about the same time to recharge the battery (to full according to the PC) as through mains so I'm guessing its reasonably efficient.

Another useful addition to the gear, I reckon.Be good, or be quick.
Rohan