Ignore this unless you are electrically minded

gracias seniore

chit
thks
plan B

Eq,

Not to get too technical, but I'd prefer to calculate it as drawing 6A at 12v, as the battery voltage will drop as it's being discharged.

I think you've hit a wrong button semewhere as I reckon a 100 Amp/hour battery will run something pulling 6A for 100/6 hours = 16.7 hours, disregarding all other factors.

Tim

ummmm..

so not to drain it past 50% or so. that would give me about 8hrs a night, so 5/6hrs of use should be feasible?

that should work
back to plan A
:)

Hi,

I'm with Tim on the calculation, but again thats in an ideal world, in reality there will be losses, and the heat itself will have an effect on the battery, plus losses in the inverter.........

It should work, but its going to give your battery a bit of a work out and a 12v dc setup would be better all round........ or......

if you must go 240v, how bout one of the cheapie 750/850w gennies... run all day on few ltrs fuel, and if you put a decent length power cord on it and leave it out of your camp, shouldnt annoy you, can be found for around $100 in bunnings.

Whilst its on, you can charge your battery with it, (recommend via a charger, not direct from 12v gen outlet, as regulation not so great on cheapies) then at night run your inverter and then you have a 24hr fan.

QED

Ron

Ron / Tim,

Yeah you are right - Still 5.2 amps not counting losses - so that equates to 19.2 hours.

100 amp/hour battery divided by 5.2 amps = 19.2 hours.

I made the error above by dividing the 72 watts into 100 (should have been the amps) - but it was past my bedtime.

Eq.

Eq,

It's only 5.2A if you use 13.8V as the battery voltage. A battery is fully charged at 12.6V, it only reads 13.8v, or higher, when being charged.

So for the fan to draw 5.2A he needs to have the vehicle running at a speed where the alternator is producing 5.2A in excess of other requirements. Therefore the correct answer to his question of how long can he run his fan would not be related to the capacity of his battery rather the size of his fuel tank. Then we'd have to know how many litres per hour his vehicle would consume at idle. That'd entertain us for hours! :-)

As an idea, if he kept his vehicle running, he could run the aircond to keep cool and duct it into his van, but that would require many additional calculations for us. Be a good way to avoid Christmas tho!

Tim

If you REALLY need a fan, buy a secondhand car A/C condenser fan from a small car and run it straight off 12 volts, Way more efficient...............

I know . I know....

but the 12volt won't touch the sides this weekend in Brisvegas.

Sat 35c
Sun 37c

typical xmas day forecast

I'm being really helpful today.

Let's not limit ourselves here. Say NO to a cute little oscillating fan, get yourself a pair of fans that go in front of the radiator to add extra air flow and mount them on a stand. Or two stands, one in each corner and you'd get a willy willy going. Those babies would push out some air, are already 12volt, and probably use less than 6A, maybe even less than 5.2A (apol to EQ)

But I guess there would be complaints about the noise - geez some people are hard to please.

Tim

Correct Rosco but I think the current was RMS value and 240 is the RMS of mains so the calc is OK

Ken

There ya go Ken

Always thought oldtimers disease would catch up with me oneday.

Cheers

.....................?????? wot's me name again???????

Yer ... that's it

Rosco

No real need to complicate things, but the EFFECTIVE mechanical power of 72 watts AC vs 72 Watts DC is exactly the same.

yes of course

uhhh.....

thks for that Dilligaf

off to Coles