# 1200w through inverter, 2 x 100amp batteries, 135w solar?



## wilse (Aug 10, 2007)

Morning all

I've 2 x 100amp batteries... brand new and 135w brand new solar cell.
I've been given a 1200w inverter like this one. According to the specification pdf file, this can do 2500w peak 8O

My question is if I want to run a hairdryer 1200w for 10 minutes how much will this take from the batteries?

I've also a nespresso coffee machine that is 1260w, from wakeup to getting a coffee it takes around 2 minutes. Could I safely get away with this?

Is there a calculation to work out [roughly] how many amps will be lost when running 240v appliances through an inverter?

cheers electro-techies

w


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## sallytrafic (Jan 17, 2006)

Just multiply the wattage by the minutes and divide by 60 to get the Watthours.

Then Divide by 12 to get the Amperehours

so for the hairdryer 1200 *10/60 = 200Wh around 17Ah or 9% of your battery capacity.

A hefty load but ok for 10 minutes a day


Note because of inefficiencies plus powering the inverter fan you will take a little more but this is ok for a rough estimate after all you wont be using a stopwatch on your use of the hairdryer will you


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## DABurleigh (May 9, 2005)

Wilse,

"My question is if I want to run a hairdryer 1200w for 10 minutes how much will this take from the batteries?"

It is not the neat calculation you would expect, because of the complexities of Peukert. My answer would be it is doable, depending on how much else you want the batteries to do before they have had a chance to recover, and the limitation you have is plate area (effectively battery capacity) forcing a reduction in terminal voltage below the operating threshold of your inverter (unspecified, as is normal with cheap Taiwanese products) rather than battery capacity per se.

In practice, half the power for half the time is a doddle, because that's what Alison uses typically in our van. But because of Peukert, your suggested requirement is a lot more than quadruple this.

"I've also a nespresso coffee machine that is 1260w, from wakeup to getting a coffee it takes around 2 minutes. Could I safely get away with this?"

Yes (subject to above comment on unknown inverter voltage threshold).

"Is there a calculation to work out [roughly] how many amps will be lost when running 240v appliances through an inverter? "

Yes, but it is simpler to ignore the voltage conversion. So, if your mains device consumed 100Watts, you would be taking that power out of the battery, plus say 10% for less than perfect efficiency. 100 watts is close to 10 Amps at 12Volts allowing for this loss, so running it for an hour would consume 10 Amp-hours, 10Ah. Now, start talking much larger power consumptions as you are, the amps out of the battery rocket, and your battery capacity rating specified at a 10A (or comparable) discharge gives an extremely rosy picture of what it will deliver, courtesy of Peukert.

Finally, don't forget to switch your inverter off when not using it, for with nothing connected to it it would run down your fully-charged batteries below 50% (guidance to maximise life) in just 4 days. Again, the problem with cheap Taiwanese products!

Dave


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## davesport (Nov 12, 2006)

> My question is if I want to run a hairdryer 1200w for 10 minutes how much will this take from the batteries?


Blinkin Flip ! How much hair do you have 

D.


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## hogan (Oct 31, 2006)

put hair in front of heater out let or see 
http://chapucillas.acmur.es/chapucilla_82.html
But you may need the help of bablefish


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## wilse (Aug 10, 2007)

hogan said:


> put hair in front of heater out let or see
> http://chapucillas.acmur.es/chapucilla_82.html
> But you may need the help of bablefish


hahahaha..... that's brilliant... why waste money on inverters! hahahaha


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## DABurleigh (May 9, 2005)

Haven't searched but I well recall MHF innovators - who correlate highly with tight buggers  - trying this and reporting that it is a flop in more ways than one.

Dave


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## 125678 (Jul 13, 2009)

*inverter*

simple forget inverter i dry my hair under the eletric roof vent


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