DC-AC Power inverter for aircraft use

Fearless Tower

Fearless Tower

Touchdown! Greaser!
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Fearless Tower
New aeroplane (Beech 18) has 12V cigaretter lighter power sockets in the cabin and I was thinking it might be nice to get a simple plug-in power inverter so that passengers could plug in a laptop.

Now, while I have a good grasp of mechanical, hydraulic and pneumatic systems....I have always seen electricity like witchcraft.

So, for those smarter than I on electrical matters...what do I need to look for so I don't blow stuff up?
 
Lessee… ~90 watt power supply, 12VDC. You need at least a 10A circuit through that cigarette lighter. Plus losses. Preferably much larger.

This isn't likely.

Tablets work a lot better as they only draw 2A or less.

There are a couple of direct DC adaptors around, at least for some laptops. This will likely work better as you won't have the inversion losses. Still a lot of power for a cigarette lighter.
 
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MAKG1 said:
Lessee… ~90 watt power supply, 12VDC. You need at least a 10A circuit through that cigarette lighter. Plus losses. Preferably much larger.

This isn't likely.

Tablets work a lot better as they only draw 2A or less.
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Is the limitation what the cigarette lighter socket itself can handle?
 
Fearless Tower said:
New aeroplane (Beech 18) has 12V cigaretter lighter power sockets in the cabin and I was thinking it might be nice to get a simple plug-in power inverter so that passengers could plug in a laptop.

Now, while I have a good grasp of mechanical, hydraulic and pneumatic systems....I have always seen electricity like witchcraft.

So, for those smarter than I on electrical matters...what do I need to look for so I don't blow stuff up?
Click to expand...

The most important thing to know is it works by smoke. If you let the smoke out it doesn't work any more. :D

To your question: inverters pull a lot of current. Even a small one (140W) will pull more than 10 amps on the 12V side. You need to check and see if you can stand that with the 1) wiring, 2) generator/alternator.

John
 
Yeah....this is sounding like a bad idea....probably not something I want to mess with in a 55 year old airplane. At least not without planning on some electrical system work.

Thanks all for the input.
 
My dell charger is a 60 watt output at 19.5v for the computer. But it draws 130 watts AC power
 
Fearless Tower said:
So, if I ever wanted to pursue this, it sounds like I would want to replace the outlet and potentially wiring to the outlet? There is currently a separate CB (I believe 10A) for just the cabin outlets. Cockpit power has its own CB.
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That would be the safe choice, yes.

John
 
http://www.alliedelec.com/tripp-lit...0AvQ31nbCdbSeyNa0zF3jYbpxoCzlLw_wcB#tab=specs

I used a 150 watt inverter like this (note cigarette lighter plug) for a long time to charge a laptop from my car. No issues

We just need to make sure it won't draw more than your wiring or CB will handle. I believe automotive wiring and fuses for the cigarette lighters are the same. Usually 10 amp.

I looked around some more and found that my charger is rated to pull 130 watts but the laptop won't always consume that much. If you are using it, and charging a drained battery at the same time, it will use about 100 watts. If you are using it with a full battery, or charging a drained battery but not using the laptop, it draws about 50 watts. This is watts at the plug so its drawing between 3.8 and 7.7 amps at 13vdc. Efficiency will vary, a cheap inverter is about 80% efficient. So add 20% to the numbers and you are at 4.5 and 9.25 amps.

So it will definitely run a laptop with a full battery or charge one with a drained battery, but running it and charging the battery at the same time may or may not trip your breaker.

You will notice there are a ton of inverters with cigarette lighter plugs that are advertised as being able to charge a laptop from a car. The automotive standard is 10 amps. You have a 10amp CB, I assume the wiring is up to that task but you might want to verify it anyway.
 
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Sac Arrow said:
Why not just get a DC power adapter? The animals exist you know.


http://www.powerstream.com/ADC-p006.htm
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Yes, but notice that none of those tell you the INPUT power. You know it has to be greater than the output, so it's going to tax the electrical system nevertheless.

There is no such thing as a DC transformer, so increasing the voltage is likely to mean there is an inverter hiding in there.
 
MAKG1 said:
Lessee… ~90 watt power supply, 12VDC. You need at least a 10A circuit through that cigarette lighter. Plus losses. Preferably much larger.

This isn't likely..
Click to expand...
If it was for a real cigarette lighter, 10 amps should not be a problem. If it's just a cigarette lighter shaped socket - that would be a different story.
 
Just an observation on power inverters or similar setups I have used in cars. Both cars I own have a small ac plug that can be used from the rears seats. I can tell you from experience that it will charge a phone, run a tablet, and works with small electronic devices. When you attempt to plug a laptop power supply into the plug, it does not have enough juice to run the computer. This would make me suspicious if a dc to ac power inverter running off a plane would have the same issue.
 
Choosing a quality brand is just as an important consideration as rated wattage. Many ebay products cut cost by skimping on input filtering and shielding. The switching noise inside the inverter will radiate out and can cause noise on intercom.
 
If it's a 55 year old plane, it may have only a generator and a small (30A) unit to boot.
Maybe consider seeing if you can't install a 2nd alternator (dedicated to a separate socket [AC]) and bypass the rectifier and regulate it for 120VAC (although the frequency at cruise could be easily 500Hz -- but you could regulate that with pulley size)
 
And, thinking out of the box, you could go to Wally-world and pick up a portable Stanley 1000-Amp Peak Jump Starter that has "110v" and USB outlets, in addition to the jumper cables. (The only penalty is another ~15# to add into your W&B calculations.)
 
MAKG1 said:
Yes, but notice that none of those tell you the INPUT power. You know it has to be greater than the output, so it's going to tax the electrical system nevertheless.



There is no such thing as a DC transformer, so increasing the voltage is likely to mean there is an inverter hiding in there.
Click to expand...


No, it's likely there's a boost converter inside.

Like...

DC-DC Boost Buck module 12V to 19V 8A 152Wmax power supply converter
https://www.amazon.com/dp/B00M3SR51Y/ref=cm_sw_r_cp_awd_UC2Vwb11C6MX6

And many other variants.

https://en.m.wikipedia.org/wiki/Boost_converter

Cheap ones can be RF noisy and that noise may fall into any of the bands of all of your radio receivers on board, depending on the speed of the switching. Caveat emptor.
 
My Toshiba laptop converts 120vac, 1A to 19vdc and 3.42A
That's 64.98 Watts. Probably it peaks at 70 watts.

So, being the crazed law breaker I am, I plugged my Vector MAXX SST 175 watt (350 watt peak)dc to ac power inverter into the 12vdc socket in a wimpy Remos GX, plugged in my laptop and the plane immediately exploded, fell out of the sky and killed a school full of kids.
Actually, nothing happened other than the laptop booting and running normally.

It's simple math. 10 amps at 12 volts = 120 watts. Don't exceed that total and everything will be fine.
 
I have a 500W inverter for aircraft use I'd make you a deal on, PM me if you're interested.
 
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