12v Power Port with a Generator system. How Does Electricity Work?

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JoseCuervo

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JoseCuervo
I have a generator, never had the plane upgraded to an alternator system.

My goal would be to install a "power port" (We used to call them Cigarette Lighters) so that I can recharge / power the iPhones, iPads, and other gadgets.

Can you do this with a generator system?

Any issues?

I don't want to fry any of the devices due to an inadequate power supply.

Anybody done this?
 
12v is 12v.

(Or 14 is 14)

Generator...alternator...your electronics won't pay it no never mind.
 
Make sure your charger is a regulated 5 volts DC type. If you install a cigarette lighter with fuse and appropriate wiring, and then plug a car charger in to that, you should be ok. For iPads and tablets you'll need the 10amp version. The iPhone will work on the 2amp version, but doesn't have enough juice for iPad or tablet. And, plugging a 10 amp charger into an improperly wired and fused cigarette lighter can cook your aircraft.

If you're gonna go fancy and install the flush mounted USB ports, you have to provide a regulated source that meets the same standards as the apple OEM products. And, each port must be wired and fused for 10 amps. Otherwise, you can destroy the li batteries and even cause the to catch fire.
 
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I wonder with the title if the OP had concerns about the alternator producing AC, and the generator producing DC. No worries there, the AC current is rectified to DC.
And as far as the suboptimal voltage on the generator, I know nothing of the requirements of the devices, or if they are protected from low voltage but it is true that a generator will not put out what an alternator does at low rpm....so one could only plug things in at cruise power, I'd think. How about a digital voltmeter plugged into the cig lighter to monitor that first?
 
Yep. In fact the generator power will actually be "cleaner". The DC you get from a rectified alternator is actually pulses of positive voltage, whereas the DC you get from a generator looks a lot more like the output of a battery. As long as you have enough total capacity in your charging system, it shouldn't be a problem.
 
You may have to run the generator at a higher RPM while on the ground or during taxi,depending on the strength of the generator.
 
Let'sgoflying! said:
, or if they are protected from low voltage but it is true that a generator will not put out what an alternator does at low rpm....so one could only plug things in at cruise power, I'd think. How about a digital voltmeter plugged into the cig lighter to monitor that first?
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Not needed. That's why you have a battery. The battery will keep the voltage in check assuming it's not dead.

I'd plug it in and not worry about it. The electrical load from whatever he wants to plug in is a rounding error compared to what his nav and landing lights likely draw.
 
Another option is an external battery, I have one and it is pretty awesome. Holds a charge for over a month, actively powers the ipad2 and the iphone at the same time; if using the 2.1a side ie it won't merely hold the charge at 65%, it will charge it to the 90's.
Plus you can throw it in your plane, car or a travel bag and use anywhere there is no charge option easily available. Solves many more problems than just the airplane one.
 
Let'sgoflying! said:
Another option is an external battery, I have one and it is pretty awesome. Holds a charge for over a month, actively powers the ipad2 and the iphone at the same time; if using the 2.1a side ie it won't merely hold the charge at 65%, it will charge it to the 90's.
Plus you can throw it in your plane, car or a travel bag and use anywhere there is no charge option easily available. Solves many more problems than just the airplane one.
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This is probably the simplist and cheapest. A good external battery pack will keep an iPad and an iPhone going much longer than a tank of gas, and much longer than my backside can stand sitting in a typical 50 year old airplane seat.

KMASHI 10000mAh External Battery Power Bank, Portable Charger Backup Pack For iPhone 6s 6 Plus and more

61a%2B2tb6CXL._SL1000_.jpg
 
Let'sgoflying! said:
I wonder with the title if the OP had concerns about the alternator producing AC, and the generator producing DC. No worries there, the AC current is rectified to DC.
And as far as the suboptimal voltage on the generator, I know nothing of the requirements of the devices, or if they are protected from low voltage but it is true that a generator will not put out what an alternator does at low rpm....so one could only plug things in at cruise power, I'd think. How about a digital voltmeter plugged into the cig lighter to monitor that first?
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Yes, I was wondering about the "quality" of power on the generator at low RPMs.. I did not want to have to remember to unplug things before descending, in order to prevent damage.
 
gasfiltered said:
Yep. In fact the generator power will actually be "cleaner". The DC you get from a rectified alternator is actually pulses of positive voltage, whereas the DC you get from a generator looks a lot more like the output of a battery. As long as you have enough total capacity in your charging system, it shouldn't be a problem.
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Thanks, that kind of answers the first worry.
 
frfly172 said:
You may have to run the generator at a higher RPM while on the ground or during taxi,depending on the strength of the generator.
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Run it higher to avoid damaging something, or run it higher to continue charging the iPad while taxing?
 
jesse said:
Not needed. That's why you have a battery. The battery will keep the voltage in check assuming it's not dead.

I'd plug it in and not worry about it. The electrical load from whatever he wants to plug in is a rounding error compared to what his nav and landing lights likely draw.
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Now that o think about it, that makes sense. My landing light does not dim/brighten based on RPM. It definitely is pulling a constant draw off the battery.

I already have the habit of shedding electrical loads as I pull off the runway. So far, never lost radio and beacon by the time I get to parking.
 
Let'sgoflying! said:
Another option is an external battery, I have one and it is pretty awesome. Holds a charge for over a month, actively powers the ipad2 and the iphone at the same time; if using the 2.1a side ie it won't merely hold the charge at 65%, it will charge it to the 90's.
Plus you can throw it in your plane, car or a travel bag and use anywhere there is no charge option easily available. Solves many more problems than just the airplane one.
Click to expand...

I was trying to get away from that solution, as I think I may have too many gadgets to carry back and forth to the airport.

But, it is the simplest solution.
 
JoseCuervo said:
Now that o think about it, that makes sense. My landing light does not dim/brighten based on RPM.
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If your generator has enough poop that you can get away with running a landing light, then the power to a USB converter isn't going to make any difference.
 
gasfiltered said:
Yep. In fact the generator power will actually be "cleaner". The DC you get from a rectified alternator is actually pulses of positive voltage, whereas the DC you get from a generator looks a lot more like the output of a battery. As long as you have enough total capacity in your charging system, it shouldn't be a problem.
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As a general rule most alternator output has been cleaned up by a capacitance installed in the system. That capacitance is usually the battery.
 
As has already been noted your system is running off the battery which is like a big tank of potential at a fixed 12 volts. The generator is simply keeping the tank full. Also most electronic devices have their own regulated charging apparatus that will work off of any input within a range such as 3-20 VDC
 
wilkersk said:
Make sure your charger is a regulated 5 volts DC type. If you install a cigarette lighter with fuse and appropriate wiring, and then plug a car charger in to that, you should be ok. For iPads and tablets you'll need the 10amp version. The iPhone will work on the 2amp version, but doesn't have enough juice for iPad or tablet. And, plugging a 10 amp charger into an improperly wired and fused cigarette lighter can cook your aircraft.

If you're gonna go fancy and install the flush mounted USB ports, you have to provide a regulated source that meets the same standards as the apple OEM products. And, each port must be wired and fused for 10 amps. Otherwise, you can destroy the li batteries and even cause the to catch fire.
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I believe you mean watts, not amps. A 12V outlet rated at 10A (which is hardly unusual) is 120W. An iPad can consume up to 12W. 2.1A at 5V, but only 1A at 12V (though the conversion isn't 100% efficient, so you need a little more). So, you'd need a lot of electronics before you've overloaded the 12V port.
 
If I was planning to add any more electrical stuff in my airplane, the first question I'd ask is how much of a load am I adding and does my system have the capacity to handle it. I believe the 4313 says continuous load shouldn't exceed 80 % of the system capacity. So if it's a 60A alternator, continuous load shouldn't exceed 48A. Do you have a current/valid electrical load analysis for your airplane?

You don't see this topic discussed much, but it's something I'm aware of because I work as an Avionics Engineer for an airline, and it can matter. It took a bit of searching and asking around to discover that the FAA used the ASTM to develop new standards for putting an ELA for part 23 airplanes in 2006.

See -> https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0ahUKEwjZsNiY-KzOAhXpzIMKHeGcDI4QFggeMAA&url=https://www.astm.org/COMMIT/FR%20F2490_05.pdf&usg=AFQjCNFaIMxGORcTAFeROHmLwEwHMhjiKA&cad=rja

I did an ELA on my airplane because I was concerned that all the gear avionics added over the years (about 10A worth) might be too much for my old airplane. I suspect that most GA maintenance people filling out the 337's really don't address the topic with any precision. I personally recognize you cannot cheat the physical laws of nature with ignorance. So I bought the spec ($50.) and did an analysis for my airplane.

I've attached some pdfs so folks (in the interest of safety) can see how I treated the subject. Basically, there are electrical system loads that are drawing current all the time and some loads are intermittent, depending on how you operate your airplane. So I have a continuous loads total that's all the stuff that's always on. I also identify intermittent loads. Recognize for example that a radio draws more power to transmit than to receive. I didn't include intermittent loads in my total of continuous electrical load.

I did take it one step further to evaluate worst case loads for various phases of flight. There the intermittent load is added to my continuous load number, so I can see what my temporary draw is. I have columns for % continuous rating, % total capacity, and actual draw when I'm pulling more than 60A, because that power has to come from the battery.

The worst case loads don't really represent realistic operating numbers because, for example, the PTT and flaps are only operated for seconds at a time. Still, there are times where (on paper) I do temporarily draw power from my battery or risk a voltage drop, which is is a good argument for not ever operating with a dead battery.

Batteries have a finite capacity rated in Amp hours so you can roughly calculate how long it will hold up with a known load, if it's in good shape. Of course all batteries are load tested at annual so that's not a concern. Bottom line, your alternator/generator simply may not be able to produce enough power to cover worst case intermittent loads.

If I wasn't an EE and Avionics Engineer in my day job with an older plane chock full of electrical stuff, I probably wouldn't have done this. I do now see some value in newer more efficient lighting gear. My upper beacon draws 11A, I'd like to cut this in half. My ELA isn't finished and isn't 100% correct (for reasons I won't go into), it's only applicable for my airplane, and it doesn't account for my Aspen display backup battery. It does give me some idea how reasonable the electrical loads are on my airplane.
 

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There's a difference between generators and alternators, and it's the reason alternators replaced generators. Most generators in small airplanes will have a capacity between 20 and 35 amps. An alternator is usually 60 amps or better. The generator's output usually drops below battery voltage once the engine's RPM falls below 1200 RPM or thereabouts, and so it is contributing nothing. The reverse current cutout relay in the regulator makes sure of that. The alternator will produce plenty of power at idle, sometimes so much that you can turn almost everything on and not see a discharge.

The alternator also weighs a whole lot less than the generator, and its carbon brushes last far longer. There are STC'd conversions available to get rid of that old generator. Automobiles stopped using generators at least 50 years ago.

The one thing a generator will do that an alternator won't: bootstrap itself into charging a totally dead battery if the engine is hand-propped.
 
kontiki, your information is really useful and credible (would be nice if you posted the Excel files instead of PDFs!!). I have a question for clarification... if the load on the electrical system at any given time exceeds the alternator's capacity will the battery make up for this deficiency without damaging any part of the system? For example if I have a 60A alternator, but for 30 minutes I need to draw a max load of 80A will my system support this? If this is true, how do I calculate how long the battery can sustain this supplementary load? Again, thanks for sharing your expertise with us!
 
Rob58, Give me a "don't care" email address and I'll send it to you. The website file attachment tool doesn't recognize .xls files.

One thing I haven't done yet is add a worksheet that lets me develop or evaluate practical emergency procedures for load shedding (day, night, VFR, IFR) for when the alternator finally does fail. Sooner or later everything fails, it's good to have options. It's the sort of thing I don't want to try working out on the fly.

In my airplane the alternator is essentially in parallel with the battery. So yes, it draws from the battery when the alternator isn't putting out enough current. I can see that by watching the current flow indicated by my AMP meter.

In my airplane, engine off, turn battery master on, turn on the beacon, amp meter (or amp meter shunt) installed between the battery and power bus shows current flow from battery. Start the engine, alternator now feeds current back into to the battery, amp meter needle points in the other direction and shows battery charging current. I look for that on pre-flights and start up. I believe Piper Arrow AMP meters are not setup like my Grumman Tiger.

My battery has a 24 Amp hour rating. Very broadly, it can supply 24A for 1 hour or 1 amp for 24 hours. Now that's a quick and dirty calculation. Battery discharge curves are not linear and are affected by environment and battery condition. The manufacturer for your battery probably publishes that data as a graphed curve for a new battery under test. Quick and dirty (which is what I did in my ELA) take the Ah rating, divide it by the discharge current and the result is time in hours. That will probably always be a very optimistic result.
 
Thanks for the explanation about battery discharge rate - it does make perfect sense and your examples are very helpful. I'm going to go through the steps in analyzing my load factors in different conditions and getting to know my electrical system better. If you would send me the Excel files that would really be appreciated! Email is rswanland - at - usa.net. Only problem now is that this post has started me thinking about a bunch of related issues... I think I will start some new threads so that I don't go off-topic from the OP. Again, thanks very much!
 
timwinters said:
12v is 12v.

(Or 14 is 14)

Generator...alternator...your electronics won't pay it no never mind.
Click to expand...

Except that the noise created by a generator is sparkies from the brushes and the noise created by an alternator is the whine of the AC being converted to DC. Pays yo' money and takes yo' choice.

Jim
 
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