Explain How Car DC Inverters Work - Fiberglass RV


Reply
 
Thread Tools Search this Thread Display Modes
 
Old 07-22-2014, 02:14 PM   #1
Senior Member
 
Name: Huck
Trailer: ParkLiner
Virginia
Posts: 571
Explain How Car DC Inverters Work

Here's a sample product: I changed name of actual product to XXXXX
Quote:
XXXXXX 200w power inverter car dc 12v to 110v ac inverter dc adapter with 3 AC outlets + 4 4.2A USB charging ports
I am showing my ignorance, but if it is a 200 w power inverter, how does it put out more than max 2 amps? (200/115 = 2)

The reason I am asking is I am trying to determine what I can run off an inverter plugged into one of my dc circuits. I recharged my laptop using a 75 w inverter and it seemed to work fine.

But if I have a 12v circuit with a 15 a fuse, aren't I limited to 180 w? Would the 200 w inverter blow my circuit?

Should I run cables directly from battery to inverter and what does this buy me? I guess more amps?

I would prefer not to run the additional cables if I don't have to. Right now, the only things that have to have ac are laptop and possibly a printer. I can run both of those with my 75 w inverter (1 at a time).

But let's say I wanted to run the microwave. In that case, would I need at least a 750 w inverter connected directly to battery?

Thanks. I'm going to get the hang of this yet.
__________________

__________________
Huck is offline   Reply With Quote
Old 07-22-2014, 02:22 PM   #2
Commercial Member
 
tractors1's Avatar
 
Name: Charlie Y
Trailer: Escape 21 - Felicity
Oregon
Posts: 1,127
Inverter wattage is how much power the inverter can deliver - each load plugged into it draws a certain number of watts. If your plugged in demand totals more than 200W your inverter can't deliver that.

If your inverter tries to pull more than 15 amps from the 12V line you will blow that fuse.

If you want more wattage you will need a larger inverter and bigger wires to the battery.

Think of the inverter as a supply you can draw from, not something that pushes energy out.
__________________

__________________
Charlie Y

Don't drill holes, try custom storage you design: http://RVWidgetWorks.com
tractors1 is online now   Reply With Quote
Old 07-22-2014, 02:28 PM   #3
Senior Member
 
Name: Darwin
Trailer: 2002 19 ft Scamp 19 ft 5th Wheel
Posts: 3,029
Send a message via Yahoo to Darwin Maring
That microwave will suck the life out of the battery very quick.

It takes the DC and they run it through a multiviberator that outputs a square wave at the correct cycle then through a transformer to get it to the required voltage (cheep one). then if you spend enough money for it they will add filtering circuitry to give you a pure AC sign wave and so on. The more you spend, the bigger unit you can get. Most will come with a direct connection to the battery as the shorter the connection to the DC the less loss. Others come with a digerati lighter plug that you just plug in. To go all out, you would install multiple batteries, controller and solar panels, etc and it gets very expensive very quick.

You can use your small inverter and plug into your battery receptacle in the camper or You can purchase a battery jump pack at the where house clubs that have jumper cables, air compressor and inverter built in and that is something to think about for the PC and Printer.
__________________
Darwin Maring is offline   Reply With Quote
Old 07-22-2014, 02:55 PM   #4
Senior Member
 
Name: Huck
Trailer: ParkLiner
Virginia
Posts: 571
Quote:
Originally Posted by tractors1 View Post
Inverter wattage is how much power the inverter can deliver - each load plugged into it draws a certain number of watts. If your plugged in demand totals more than 200W your inverter can't deliver that.
I think this addresses my 1st question, so let me be more specific. The inverter is 200 w, so at 110 v, that's a little less than 2 amps (P(W) = I(A)◊ V(V)).. So how can it support 3 ac outlets and 4 4.2a usb ports? Where are all the amps coming from?
__________________
Huck is offline   Reply With Quote
Old 07-22-2014, 03:27 PM   #5
Moderator
 
Name: RogerDat
Trailer: 77 Scamp 13
Michigan
Posts: 3,080
What you plug into the 4 outlets determines the draw so "what it can support" is not much draw. More you pull the more it pulls from the battery. But you are correct 2 amps is about it. And you will be drawing 20+ amps from the battery. Which can comfortably handle that for less than 3 hrs. on a 100 amp hr. battery.

So you can charge a couple phones and your laptop. Or run a 110 light or maybe a fan.... But I'm thinking not going to run a coffee pot.

Might find this table of use. Usage Chart: How Many Watts Do You Need?

200 watts is fine for running a laptop, charging a camera, or running a hand held DVD player but next to useless for most appliances. As someone already pointed out you end up needing dual batteries and solar to support things such as appliances.
__________________
RogerDat is offline   Reply With Quote
Old 07-22-2014, 03:35 PM   #6
Senior Member
 
Name: Darwin
Trailer: 2002 19 ft Scamp 19 ft 5th Wheel
Posts: 3,029
Send a message via Yahoo to Darwin Maring
Now, when you charge your laptop from the inverter the laptop power supply takes the AC and turns it back to DC. If your laptop operates off of 12VDC, skip the inverter altogether and charge it directly from your 12VDC supply. They sell cigarette plug devices that plug to the laptop to do just that.
__________________
Darwin Maring is offline   Reply With Quote
Old 07-22-2014, 03:46 PM   #7
Senior Member
 
Name: Huck
Trailer: ParkLiner
Virginia
Posts: 571
Quote:
Originally Posted by Darwin Maring View Post
Now, when you charge your laptop from the inverter the laptop power supply takes the AC and turns it back to DC. If your laptop operates off of 12VDC, skip the inverter altogether and charge it directly from your 12VDC supply. They sell cigarette plug devices that plug to the laptop to do just that.
I've got that part down. It just seems to me that these devices magically create amps. I understand the amps come from the battery, but the devices seem to pull more amps than the power rating they have allows.
__________________
Huck is offline   Reply With Quote
Old 07-22-2014, 03:54 PM   #8
Senior Member
 
Bob Miller's Avatar
 
Name: Bob
Trailer: 1973 Hunter Compact II
California
Posts: 7,912
You are assuming that each outlet has it's own rating of 200 watts, that's not correct. It's a total of 200 watts from all three outlets combined, and that's a peak power rating. If you look at the specifications it will probably say something like 150 watts continuous. And the USB outlets aren't a part of the inverter at all, they are a separate 12VDC to 5VDC reducing circuit, but do add to the total DC load.
__________________
Bob Miller is offline   Reply With Quote
Old 07-22-2014, 04:58 PM   #9
Senior Member
 
frank_a's Avatar
 
Name: Frank
Trailer: 2012 ParkLiner #006
New York
Posts: 2,204
Quote:
Originally Posted by Huck View Post
I've got that part down. It just seems to me that these devices magically create amps. I understand the amps come from the battery, but the devices seem to pull more amps than the power rating they have allows.
Huck, when you get this figured out, key me in would ya?

Frank
__________________
2012 ParkLiner #006
2013 4wd Escape 2L Ecoboost with 3500# tow package
frank_a is offline   Reply With Quote
Old 07-22-2014, 05:10 PM   #10
Senior Member
 
Name: Huck
Trailer: ParkLiner
Virginia
Posts: 571
Quote:
Originally Posted by frank_a View Post
Huck, when you get this figured out, key me in would ya?

Frank
Everybody else knows. They just won't tell us!
__________________
Huck is offline   Reply With Quote
Old 07-22-2014, 05:11 PM   #11
Senior Member
 
frank_a's Avatar
 
Name: Frank
Trailer: 2012 ParkLiner #006
New York
Posts: 2,204
Quote:
Originally Posted by huck View Post
everybody else knows. They just won't tell us!
lol!
__________________
2012 ParkLiner #006
2013 4wd Escape 2L Ecoboost with 3500# tow package
frank_a is offline   Reply With Quote
Old 07-22-2014, 06:10 PM   #12
Senior Member
 
Timber Wolf's Avatar
 
Name: Tim
Trailer: '88 Scamp 16, layout 4
North Florida
Posts: 1,440
This stuff hurts my head. While investigating running my CPAP off a battery and inverter I found contradictory information on the subject. The machine says 120V and 2.5A on the bottom. So, that would indicate 300 watts right? But, upon further investigation I discovered that the CPAP manufacturer recommended a 150 watt inverter. I ordered the inverter (150W) that they recommended and what do you know, my CPAP runs just fine on the half-sized inverter.
__________________
Timber Wolf is offline   Reply With Quote
Old 07-22-2014, 06:31 PM   #13
Moderator
 
Name: RogerDat
Trailer: 77 Scamp 13
Michigan
Posts: 3,080
I think one only needs to convert watts to amps on the demand side if amps are not provided. Some devices might say 110 volt @500 watts a different device might specify volts and amps or even possibly all three. But most of the time I only see 2 values given.

I think while the device may be built to work with a 110 volt input that does not mean internally it uses 110 volt current. Simplest example I can think of is your computer. Plugs into 110 source but everything inside is either a 12 volt or 5 volt circuit.

On the other hand something such as a blow dryer that is 1000 watts is using that 110 volt internally and then the formula would yield the correct amperage draw.

This might also explain the CPAP machine, internally it may not be using 110 volt. It just needs 110 volt input to have the correct voltage output on the components using the power. Watts required are based on what uses the power.

And this hurts my head and my whole face.
__________________
RogerDat is offline   Reply With Quote
Old 07-22-2014, 06:35 PM   #14
Senior Member
 
Name: Darwin
Trailer: 2002 19 ft Scamp 19 ft 5th Wheel
Posts: 3,029
Send a message via Yahoo to Darwin Maring
I have decided to run some AC through a transformer and convert some of the volts to amps.
__________________

__________________
Darwin Maring is offline   Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Explain Kevin K General Chat 52 06-27-2009 07:24 PM
Please explain ??? Bill K Towing, Hitching, Axles and Running Gear 8 03-26-2009 11:05 AM
Border Bike Rally (& Car Show), Bike & Car Weekend event (ON S John J. M Rallies, Get-togethers, Molded Meets (Archive) 1 06-07-2008 07:28 AM
randy please explain that bear! potteralice General Chat 0 05-19-2006 05:58 PM
Explain Atwood Heater jefh Problem Solving | Owners Helping Owners 6 12-15-2005 01:35 PM

» Upcoming Events
No events scheduled in
the next 465 days.
» Virginia Campgrounds

Reviews provided by


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 11:49 AM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.