SD-8 Alternator
 

Anybody using the B&C SD-8 alternator as their only source of juice? If so, what sort of electrical equipment have you got? I'm building a Day-VFR plane and am thinking this approach might work real well.

Steve Zicree

Not Enough
 

Steve,

The SD-8 on my -7 backs up the 40 amp alternator on an all-electric aircraft. I've played with it to find out how it performs should I ever need it. The SD-8 is 8 amps max, and it puts out very little juice at idle rpms, even well up into cruise there's little left after a few loads and IR losses nurse off it. (I wonder if it's not really a generator; it's permanent magnet and I don't know if the regulator also contains a rectifier.) The net consequence is that your starting battery is going to gradually die for lack of recharging.

The installed cost of an SD-8 is hundreds of dollars more than an alternator, it is only ounces lighter, and a more complex installation since it needs individual regulation components. Other than back-up for dual electronic ignition, I wouldn't install one. Even then, my current project is going to be dual battery rather than SD-8.

Oh, yeah. The SD-8 interferes with the sender if you use Van's tach, thus making you buy a tach cable and finding a place to hang the sender instead of simply screwing it into the back of the accessory case.

In short, a lone SD-8 makes a wimpy, expensive, clumsy source of electricity.

John Siebold

How about GAMI's Supplenator?

Not sure of the price, but it's self exciting and rated at 30 amps.

Brad

Why not?
 

Not to disagree I know of a RV-4 with this set up and I heard no complaint. I love the idea of a simple day VFR RV. I looked into this. For bare bone VFR cruise I got about 4-6 amps, for worst case everything (Comm. transmitting, flap motor running, boost pump on) 9.1 amps max*.

So a 8 amp PM alternator would work. Why not? You just can't go digital all electric panel and battery dependant Electronic ignition (EI). It has been done before with a basic VFR panel. With that said, a little fairly inexpensive 40 amp ND belt driven alternator can bolt to the front of the engine, or even a small 20 amp John Deer PM alternator. With the installed weight of a ND alternator at about 7lbs and low cost this may be more practical. You have the flywheel pulley there and nothing that needs to go in that space why not?


G

* You could drop almost 1 AMP of continuous load by replacing the battery contactor (relay) with a cool Kilovac (Tyco) relay that uses very little power to stay closed. It works on 12v and can handle 12-900V at 500amps continuous, weighs less than 1lb, is small and has magnetic latch relay. It is not like a latching relay that stays latched if power is removed, which could be bad. The current to keep the SPST relay closed is 0.13 amps. Typical "HOT" relay is almost 1 amp.

Awesome info from everybody. Thanks a million. Now my next question is where do I get a good alternator? I suppose 30 amps should be more than enough for me. I'm still on the fence regarding the OV protection/internal/external regulator thing and would appreciate advice on this as well.

Steve Zicree

SD-8 Install Picture?
 

Would someone please post an SD-8 install picture, or two? Specifically, I have an SD-8, and I'm planning to install it on my Lycoming angle-valve's vacuum-drive pad, but I'm wondering about the clearance with the tach drive. Will a tach drive 90-degree adapter clear the SD-8 okay, or do I need to use a tach cable to remote-mount a tach drive sensor?

Thank You,

Bill Palmer
RV-8A In-Work

I am solely using an SD-8 on my day/night VFR -4 with no problems, at engine overhaul I replaced it with a new SD-8 and B&C said it would actually put out about 10A at an engine speed of 2450. I run KX155 nav/com, German 396, Rnav FC-10 fuel computer, intercom with one Bose ANR head set, the old one that uses power from the plane not remote battery powered, and engine gauges. I can even fly an hour or so with the nav lights on and still start the next day but I don?t think it is quite keeping up with the lights. I normally keep the plane plugged in to a battery tender but have also made many cross country flights/trips for more then a week and never had an issue maintaining the battery with ought plugging it in. This won?t work for everybody but for a basic VFR plane it does very well and is simple and clean.

Mine is on an IO-360 angle valve and as far as the tack goes mine is an Electronics International and I don?t know where it gets its signal but the tack output on the Acss case is caped and I don?t remember if it would interfere with it or not, it must be getting its signal from a mag would be my guess.

Over load protection is important. I had an "automotive" alternator fail and charged my system with 18+ volts. Cooked my EFIS stand by battery $30, and was suspect in weakening my BMA EFIS1 mother board ($900 a month later). A friend of mine had the same "auto" alternator, cost him $2,500 in fixing a Dynon, radios & transponders when his failed full power. We both replaced ours with an alternators from Plane Power.

Take a look at Plane Power. Over load protection, lite weight, and 2 year warranty from DATE of purchase.

http://www.plane-power.com/

BTW, Van's now recommends, & sells Plane Power alternators.

The Supplenator is intriguing, but the illustration at the top is a 3D Cad drawing (evidently, there is no actual product available for a real photo to be taken), plus the last update of that page was in "1-17/02".

Does that product even exist yet?... or will it ever?

I think if push came to shove, I'd vote for 8 Amps of real power (SD-8) over 30 Amps of nothing.
The SD-8 has been around a long time and has proven to be not only a reliable back up power generator, but a good stand-alone power generator for lightly equipped day/VFR aircraft.
That said, it would be nice if the Supplinator were an actual product you could put your hands on.

Picture of SD-8 Install
 

Bill, you can see the SD-8 installed on my engine in the following picture post:

http://img207.imageshack.us/my.php?i...onstandlz5.jpg

It is the orange item installed on the accessory case (replaces the vacumn pump) next to the 90 degree oil filter adaptor.