Is 12.8 AMPs enough ?

Tom-D

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Tom-D
I'd like to install a B&C alternator in the VariEze, there is no starter, no exterior lights, just a battery to charge and radios to run.

There are no alternator between the 12.8 AMP and the 30 AMP. I think the 30 AMP is a little much.
 
12.8 amps is a lot of radio.

If memory serves me correctly, the Cessna 120 I flew had a 15 amp generator that ran a radio, transponder, nav lights, starter, etc. If you used the landing light it would fall behind and eventually the battery would go flat.

My Rotax gives about 18 amps - radio, gauges, transponder, starter - no problem.
 
What's the concern? Weight? Physical size? I've never heard anyone complain about too much alternator. Your electronics are gonna draw what they're gonna draw and no more, the larger alternator isn't going to overcharge anything, and there would be extra amp capacity for future upgrades if desired. All else being equal I think I'd want the larger output.
 
I've had a 12A Delco Generator in my Fly Baby since 1996. Starter, radio, transponder, lift seat, nav lights, strobe (although the last two are rarely used). No issues, never been low on juice. Should be no issue on the Eze.

Ron Wanttaja
 
You sure you don't want lights or a starter? I thought you were going to build this plane to sell it, no lights or starter would really narrow your market, especially if you're rigging the panel IFR.
 
KX 155 requires a 10 amp circuit breaker. It would pull under that in transmit mode. You need to add up all your electrical load to answer your question.
 
P=VI or Power (Watts) = Volts X Amps.

You don't tell us the voltage, but at 12V 12.8amps is 153.6 Watts, at 24V it's 307.2 Watts. Look at the equipment you want to run and add up the wattage requirements from the spec plates. It should be pretty simple math, add a little fudge factor in there. Oh, and don't discount charging that battery, especially if it will sit for a long time between runs.
 
You probably need a voltage regulator in there too to make sure you don't burn up the battery.
 
All correct, but the quick answer is with no starter, and no landing lights, maybe some led POS lights, a comm and a transponder, you should be well under 10 amps continuous draw. My rv averages about 5 amps continuous with the usual items on. So with 10 amps cont that leaves 2 amps to charge the battery for the times it draws above 12 amps like withe the mike keyed and the transponder pinging.

Bob
 
You sure you don't want lights or a starter? I thought you were going to build this plane to sell it, no lights or starter would really narrow your market, especially if you're rigging the panel IFR.

I have considered adding a starter, lights, and the equipment to make it a night IFR aircraft.

BUT: It's cost prohibitive, upgrading to a Dynon Glass, complete system will cost more than the aircraft will ever sell for.

The name of the game in Variezes is keep them light so they can go fast. The major portion of the V/EZs do not have starters, the owners don't mind hand propping them.
The Canards do not like rain and bad weather, this aircraft does not have the Rontz canard, which is a bit more forgiving of rain, but still not a great aircraft to take into the clouds. So the question became "Why equipped it to do that?" So if you are not going that route, why not go 100% the other way? (day VFR)
So far I have dumped a non working auto pilot, 2 mags & harnesses, a rats nest of wires to support the Blue mountain EFIS the VHF radio and transponder plus a heavy Cessna alternator. We will replace them with dual electronic ignition, and a B&C 12.8 alternator net weight savings of about 10-15 pounds.
Other than the basic VFR day required instruments, What else would I need?
The radios I have selected are the new German electronic light weight, 2.125" instrument hole VHF with a 2 place intercom and Transponder which includes the ADS/B in and out ready. (also fits a 2.125" hole) For cross country uses Stratus and my iPad, with the proper App, like FF or ?

any suggestions will be considered. :)

Light, sweet, simple and cheap. Try to remember we do try to make a profit. Plus you know there isn't a reader/member here that would pay the money that it would require to add the Dynon.
 
Pro mechanics should know how to do load calcs.

Lots of Supercuts are flying with the B&C 8A alternator and those planes have full electrics incl starters.
 
Ok. I've got to ask. What does having a starter have to do with an alternator? Starters run of a battery.

Or am I missing something?
 
Ok. I've got to ask. What does having a starter have to do with an alternator? Starters run of a battery.

Or am I missing something?
With out a starter you can design a system with light gauge wire, and a much smaller battery, saving weight in both items.
Small batteries do not require high amperage to charge quickly.
 
With out a starter you can design a system with light gauge wire, and a much smaller battery, saving weight in both items.
Small batteries do not require high amperage to charge quickly.

So, an indirect potential dependence. A starter probably means a bigger battery. And a bigger battery will benefit from more charging current. Ok. I can accept that.
 
also, a starter draws a lot of amps out of a battery, so it takes a while to replace that juice, with a low output alternator you may not get the battery charge up after a short flight to have enough to start it again. the excess amperage from the alternator is what charges the battery.

bob
 
Makes sense Tom.

If I were looking for a commuter plane, I'd be willing to pay for a IFRed canard, but I totally hear what you're saying.
 
also, a starter draws a lot of amps out of a battery, so it takes a while to replace that juice, with a low output alternator you may not get the battery charge up after a short flight to have enough to start it again. the excess amperage from the alternator is what charges the battery.
What you say certainly makes sense, but it's not my experience. I've got a C-85 with the stock Delco 12 amp generator, starter, radio, transponder. I fly generally 35-40 minutes. In the ~20 years I've owned this airplane, I've never had a low battery except from leaving the master on. And I'm using an Odyssey battery, which, I understand, has less capacity than the gel cell I was running before.

While the starter uses a lot of amps, the actual *duration* is trivial... so the watt-hours is low. ~80 amps for 10 seconds is a quarter of a watt-hour. Probably what my radio uses, and likely less than the transponder.

Ron Wanttaja
 
Makes sense Tom.

If I were looking for a commuter plane, I'd be willing to pay for a IFRed canard, but I totally hear what you're saying.
If you were looking for a solid IFR commuter you'd not be looking for a V/EZ. By the time you load them with gear for IFR they won't hold anything else, and they slow way down.
 
What you say certainly makes sense, but it's not my experience. I've got a C-85 with the stock Delco 12 amp generator, starter, radio, transponder. I fly generally 35-40 minutes. In the ~20 years I've owned this airplane, I've never had a low battery except from leaving the master on. And I'm using an Odyssey battery, which, I understand, has less capacity than the gel cell I was running before.

While the starter uses a lot of amps, the actual *duration* is trivial... so the watt-hours is low. ~80 amps for 10 seconds is a quarter of a watt-hour. Probably what my radio uses, and likely less than the transponder.

Ron Wanttaja
What does your generator weigh? the cables to it? and the battery? what does all that weigh?
I can do the whole system for less than 5-6 pounds including the battery.

http://www.aircraftspruce.com/pages/el/alternators_bc/alt200g.php = 3.4 pounds
 
What does your generator weigh? the cables to it? and the battery? what does all that weigh?
I can do the whole system for less than 5-6 pounds including the battery.

http://www.aircraftspruce.com/pages/el/alternators_bc/alt200g.php = 3.4 pounds
Tom, please re-read my posting. I was not claiming my system was somehow superior; I was merely pointing out that another poster's speculation that the power usage wouldn't balance with a 12A generator didn't hold true in my case.

My generator, my cables, my battery, etc. may weigh more than a brand-new system, but they were paid for long ago. I don't need to shell out hundreds of dollars to lighten my Fly Baby by a couple of pounds. Cheap (read, "free") has a technical elegance all its own.

A few months back, my original Delco regulator gave up the ghost. I had the choice of buying a new Zeftronics unit, or replacing the whole system with a B&C. Got a friend with a used one, complete with the Continental gear, he was willing to sell me cheap.

Decided against it installing it, for a number of reasons. One of which was it wasn't just a plug-in replacement. I accepted that a new regulator would be needed, but there was additional protective circuitry and a capacitor that not only would need installing, but need installing inside the fuselage, not on the firewall. Replacing a single three-terminal box with another was a heck of a lot less work.

Still bought the B&C, against the day the 'ol Delco generator goes bad.

Ron Wanttaja
 
I'd like to install a B&C alternator in the VariEze, there is no starter, no exterior lights, just a battery to charge and radios to run.

There are no alternator between the 12.8 AMP and the 30 AMP. I think the 30 AMP is a little much.

Talk to me about the radios. How many, make'n'model, and all that good stuff.

Don't add up MAXIMUM current draw. Max current on a com radio is in the transmit mode and the listen/talk ratio is above 95% listen, 5% talk. That 5% is what the battery is for. You recharge it in the 95% listen mode, which if somebody did their homework in the design is well below an amp.

My opinion is that the 12 amp generator will work just fine with one com and an ADS-B transponder system. A 5 amp generator would probably work just as well.

Jim
 
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Talk to me about the radios. How many, make'n'model, and all that good stuff.

Don't add up MAXIMUM current draw. Max current on a com radio is in the transmit mode and the listen/talk ratio is above 95% listen, 5% talk. That 5% is what the battery is for. You recharge it in the 95% listen mode, which if somebody did their homework in the design is well below an amp.

My opinion is that the 12 amp generator will work just fine with one com and an ADS-B transponder system. A 5 amp generator would probably work just as well.

Jim
I'm starting to believe even the 8 amp would work, with radios (Funkwerk) at 120 ma. no exterior lights, manual gear extension. I could go with no Alternator, and simply re-charge the little battery after each flight.
Or... run the aircraft with a hand held radio and simply eliminate the electrical system.
The ATR833-LCD is a complete solution for radios in small aircraft with the new channel separation of 8.33kHz. The channel spacing can be switched between 25kHz and 8.33kHz. The built-in VOX-controlled intercom operates up to 4 microphones and all headsets are separately adjustable. The user can define up to 100 named frequencies to build up an own database. All stored frequencies can be searched via name. The ATR833-LCD transceiver fits in a standard 2.25" instrument panel hole and is 6.3" long (without connectors -- allow 2" for connectors and cables).
Features:
• 760 channel VHF transceiver
• compact - fits in 2.25" round hole in instrument panel
• dual-watch technology, simultaneous monitoring of two frequencies
• fast alphanumeric database search
• built-in VOX intercom for up to 4 microphones
• memory for up to 100 user-definable named frequencies
• full 6W carrier output
• auto TX cut-out after 2 minutes
• German quality -- full two-year warranty
Technical Data:
• frequency range: 118.00MHz - 136.975MHz
• 8.33kHz/25kHz channel spacing
• HF output power approx 6W
• audio output power approx 4W
• weight: approx 1 lb 9 oz
• power consumption: approx 120mA standby; 1.8A during transmission
• power supply: 10.5V – 14V
• supplied with connector; optional pre-wired harness available
 
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I'm starting to believe even the 8 amp would work, with radios (Funkwerk) at 120 ma. no exterior lights, manual gear extension. I could go with no Alternator, and simply re-charge the little battery after each flight.
Or... run the aircraft with a hand held radio and simply eliminate the electrical system.

Guys in the Fly Baby world use either option with good success. Also, you then don't have to have a transponder unless you actually enter the Class B airspace (e.g., 30 nm veil doesn't count). Unless the Varieze had been originally certified with the electrical system of course (and the records reflect it).

I've thought about adapting the power modules from handheld tools...the little Ryobi, etc. modules that just click into the bottoms of various tools. Have a socket on the airplane, with recharging capability for two or three back in the hangar. Carry a spare or two on a cross-country.

The portable packs are 18 volts, and the challenge would be to make an 18-12V converter that doesn't waste too much juice. They do come in Lithium-Ion units, so the weight's not bad.

Ron Wanttaja
 
Tom, I was looking for a panel mount ammeter and came across this. It'll measure 0-30 volts and up to 15 amps. There isn't a shunt, you would have to wire your alternator output through the gauge. It is available with a red, blue, or green LED display.

It weighs just .3 ounces according to the product info, but I think maybe that should be 3 ounces. The cost is right, just $19.99 with free shipping if you have Amazon Prime.


41k5%2BO6ufoL._SS160_.jpg
51bcc7kx15L._AC_UL160_SR160,160_.jpg

Here's a link to the installation diagram:

http://ecx.images-amazon.com/images/I/71TgFdMYgCL._SL1500_.jpg

And the page for ordering it:

http://www.amazon.com/dp/B01CG1CU7G/ref=twister_B01CG1CRUG?_encoding=UTF8&psc=1
 
The 12A B&C permanent magnet alternator works great in my VariEze. I have a Garmin 480 (2.5A / 5A xmit), an AvMap Ultra EFIS (0.1A!), a LightSpeed electronic ignition (1.5A?), a homemade LED landing light (1A), an SL70R transponder + encoder (1A) and that's it as far as electrical equipment. I occasionally plug in heated socks. I fly IFR from time to time. I have Aveo PowerBurst Plus nav/strobe lights on the winglets but power them with batteries recessed into the winglet (didn't want the hassle of running wires). I think an 8A alternator would be OK if you can keep the load similarly light.

Tom: Are you still doing engine overhauls? I might be interested in having you do my O-200A...
 
Ohms law sez that the TRT800H-LCD xponder will draw about 18 amps on reply. In this area it will be making a reply about every second or less.
 
Ohms law sez that the TRT800H-LCD xponder will draw about 18 amps on reply. In this area it will be making a reply about every second or less.
YGTBSM. there isn't a transponder in GA that requires that much amperage. most are wired with 20 gauge wire.

IAW the AC 43.13-1B you'd be required to have a 16 gauge wire to draw 18 amps continuous in a bundle, (5feet)
 
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