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 12/120V inverter again
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albertok
New Member

3 Posts

Posted - Jul 07 2009 :  11:05:14 AM  Show Profile  Reply with Quote
quote:
Originally posted by audioguru

3000W is way too much for an inverter. If you use only 12V then its battery current will be 300A!
You would need to have a large room full of batteries to power it for a short time. Then it will take 1 week the charge the batteries.
Its wiring must be huge and it would need 48 output transistors and many driver transistors.
Its transformer would cost a fortune.




Why do you keep saying that it's not possible to make an 12V 3000W inverter? And that you would need a room full of batteries?? It simply is not true and you know it.

A well built 12V 300W inverter consumes about 300A at full load give or take. Well, that said I think you would agree with me that it's not impossible nor dangerous to take 55 Amps out of a small vehicle 55Ah battery, right? Neither is it any more danger involved in taking off 300Amps from a 300Ah battery, (given you know what you're dealing with), it CAN KILL YOU, but not because the battery is programmed to explode like you try to scare people with. So you probably should stack up with a couple of heavy duty 230Ah batteries.

3000W inverters have been around for a long time running on 12V, but given the high amperage you're dealing with it's more than twice as dangerous as a 3000W 24V inverter.
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albertok
New Member

3 Posts

Posted - Jul 07 2009 :  11:11:34 AM  Show Profile  Reply with Quote
Furtermore it's worth to say about heavy cables and large inverters that for any 12V invertes from a few hundred watts and up, it is absolutely nessesary to keep cable lenghts to a minimum. Unless you have a wery deep wallet :)
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audioguru
Nobel Prize Winner

Canada
4218 Posts

Posted - Jul 07 2009 :  3:09:10 PM  Show Profile  Reply with Quote
A battery rated at 300Ah is tested with a 30A current, not 300A.
Cold Cranking Amps are tested for a very short duration.
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albertok
New Member

3 Posts

Posted - Jul 07 2009 :  4:14:22 PM  Show Profile  Reply with Quote
I'm not talking about CCA, I'm talking bout if there is a chance for a battery to blow up when you draw from it Amps in the range of its rated Ah capacity. It will not. I have never had any of my approx. 55Ah car batteries that's been fitted to my car blow up even when I draw up to 200 Amps. 30 Amps run just by turning the key, another 75 - 150 when I crank it. Comes close to 200. When that's said I'm also aware of it's intended purpose, and the fact that you'd drain it extremely fast. But for testing purposes it's close to ideal because you get quick response from the battery when you test your low voltage cut-off, and voltage regulator. You just turn off your charger and voltages drop fairly quick.

Also something I forgot to mention earlier is the main reason many people buy 3000W inverters in the first place. Some just want to be able to run 1000W power-tools for a few seconds at a time now and then, some want the convenience of haveing a microwave owen in their trailer, boat or cabin. Most do not intend using its full rated power for an extended period of time.

Edited by - albertok on Jul 07 2009 4:23:22 PM
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antish
New Member

Ethiopia
1 Posts

Posted - Aug 20 2009 :  2:48:23 PM  Show Profile  Reply with Quote
i have a problem in 12/24vdc input to 220/230vac output with 4000w and above.please help me to do that
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superchad
New Member

3 Posts

Posted - Oct 30 2009 :  4:32:06 PM  Show Profile  Reply with Quote
hi i saw this simple inverter when googling schematics for and inverter, i saw that it might have problems, well i need to know what would best for me, i need to make an inverter that is about 75 Watts to 100 Watts (for using a laptop in a car) i want it to be as simple and cheap as possible. thanks in advance.
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audioguru
Nobel Prize Winner

Canada
4218 Posts

Posted - Oct 31 2009 :  12:16:01 PM  Show Profile  Reply with Quote
This week, Canadian Tire store is selling a Name-brand 150W inverter for $19.99.
It would cost about $60.00 to make one.

They also have an 800W one on sale for $59.99.
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superchad
New Member

3 Posts

Posted - Oct 31 2009 :  5:19:14 PM  Show Profile  Reply with Quote
i estimated the originaly circuit aaron posted at around $20 to $30 to make (for the parts) i want to make one someday so id like to have the link to schematic for one.
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audioguru
Nobel Prize Winner

Canada
4218 Posts

Posted - Oct 31 2009 :  8:36:31 PM  Show Profile  Reply with Quote
The inverter here does not work.
You can make a simple square-wave inverter that does work (but poorly) for the same low cost.
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00milind
New Member

India
1 Posts

Posted - Nov 01 2009 :  01:31:41 AM  Show Profile  Reply with Quote
Looking for a pure sine wave inverter design, 48V to 240V, 50Hz, if anyone can help I would appreciate it.

TEXA
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Darkthero
Apprentice

USA
51 Posts

Posted - Nov 04 2009 :  03:48:38 AM  Show Profile  Reply with Quote
i didnt take time to read all the above posts but i have posted a pic of the circuit . i have made changes, and it dose work this way. i got it sitting next to me running as i type this. notice the caps. and yes Tantalum caps do have a polarity. http://img522.imageshack.us/img522/952/inverter.gif
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Darkthero
Apprentice

USA
51 Posts

Posted - Nov 04 2009 :  03:50:30 AM  Show Profile  Reply with Quote
dont ask why im not entirely sure why. but i accidentally placed them like this and it functions
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Darkthero
Apprentice

USA
51 Posts

Posted - Nov 04 2009 :  05:37:48 AM  Show Profile  Reply with Quote
http://img522.imageshack.us/img522/952/inverter.gif
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audioguru
Nobel Prize Winner

Canada
4218 Posts

Posted - Nov 04 2009 :  3:33:23 PM  Show Profile  Reply with Quote
quote:
Originally posted by Darkthero

dont ask why im not entirely sure why. but i accidentally placed them like this and it functions


You corrected the error of the backwards polarity of the capacitors.

But you did not correct the error where the transistors have avalanche breakdown when the capacitors try to drive the bases to -23V (the max allowed voltage is only 7V). The avalanche breakdown causes extremely high currents in the capacitors that causes them to explode even when their polarity is corrected.

You also did not correct the error where the base current for the transistors is much too small.
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Darkthero
Apprentice

USA
51 Posts

Posted - Nov 04 2009 :  4:04:52 PM  Show Profile  Reply with Quote
quote:
Originally posted by Darkthero

i didn't notice those. but the way i have it now its putting out 130v and low amps and my caps havent exploded yet

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