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How many of you guys have standby alternators?

pierre smith

pierre smith

Well Known Member
My alternator went TU on Sunday on the way back from the coast, so I turned everything off except the comm. We only had 15 minutes to go so all was well.

It was daytime so no problem but if I'd been IFR in IMC, might be a tad difficult, so I got to thinking about the vacant vacuum pump pad and also the empty mag spot (I have one mag, one Lightspeed).

My buddy says that B @ C has either an 8 amp or 20 amp standby kit we can add.

How difficult is it to add to an existing electrical system?

Thanks,
 
When I converted to dual Electronic Ignition I added the SD-8 for a back up power source. Pretty simple to install and works as advertised, I can easily run everything required to continue a flight to a convenient stopping point should the main alt go TU.
 
I'm installing the B&C SD-8. Lighter than all but the smallest backup battery, and won't run down. The Aeroelectric Connection has plenty of wiring diagrams to facilitate integrating it with your existing electrical system.
 
We've been flying with an SD20 on the pad for 800hrs. I sure like knowing it is there, and we test it often.
 
pierre smith said:
My buddy says that B @ C has either an 8 amp or 20 amp standby kit we can add.

How difficult is it to add to an existing electrical system?
Click to expand...

I have the SD-20. Physically, it can be pain, especially with the engine mounted. There is one bolt that I made a custom tool to tighten. I didn't want to take the mag off, but I did remove the oil filter. It's probably not a big issue with the mag off. You can see the bolt in the photo below. I had to cut off a wrench to about 1.5" long to tighten that nut.

FP05022011A0005E.jpg


Electrically, it's not that big of deal. Is your electrical system based on one of Bob Nuckolls' designs? I would refer to one Bob's designs as a point to determine what you actuall need. I have a Vertical Power unit, which makes installing the backup alternator almost a no-brainer.

As you can see, it's a nice fit on the vacuum pad.

FP05022011A0005D.jpg
 
Pierre

I have an SD 8 mounted to the vac pump pad that was designed into my system from the get go (Nuckoll's all electric on a budget design). I check it as part of my run-up checklist before every IFR flight, works great.

While checking my amp draw during normal ops, I rarely see over 5 amps total draw. I am confident that the 8 amps will get me home no problem with few restrictions. Autopilot, Radio, xponder and GPS no problem.

Integration into your system will be the only issue.
 
Thanks guys....

Does it simply spin when it's not needed and then the field activated if it is needed?

Seems that would increase its life if the regulator remains inop.

Best,
 
It's a small world!

One of the dealers for the "Supplenator [$3995:eek:] told me about a gentleman in Evans, Ga, 40 miles from me, who has built a RAT...Ram Air Turbine, that a lot of Military and airlines have as a standby. It folds out into the airstream and only runs when needed:

www.basicaircraft.com. He sells quite few to Stearman, J-3 Cub, Luscombe and others with no electrical system...$2195.

Best,
 
SD-8 Integration

See the Aeroelectric forum on Matt's website. A lot of discussion regarding backup alternators.

http://www.matronics.com/digest/dig...=html&Chapter=2011-05-02&Archive=AeroElectric

Bob Nuckol's Z13/8 architecture is what I used on my -8A. The SD-8 provides enough juice to operate essential gear if the main alternator ges bad. I also have internal batteries in my 496 and AFS 4500.

SD-8 is cranking out trons whenever the motor is running. To energize the backup circuits requires 3 switches:

BATT/ALT - BAT (assuming main alt is inop)
ENDURANCE BUS ALT FEED - ON
AUX ALT - ON

Minimum of 8 amps as long as the motor is turning. A great backup capability.

I felt the SD-20 was overkill. Too heavy and excess amps.
 
pierre smith said:
Does it simply spin when it's not needed and then the field activated if it is needed?

Seems that would increase its life if the regulator remains inop.

Best,
Click to expand...

The SD8 is always on but is disconnected from the buss or battery until needed, with no load on it, it's just along for the ride.

The SD20 could be wired either way I believe (always on or off) but in any case, with no load on it it's just spinning.
 
I put the SD-8 on my 9A

Built that way as I wanted the backup. 1 Mag and 1 Light Speed.

Only need to use it once when the #1 reg. went out. Was still able to make my 20 minute flight to Vans Home Coming and then return.

Kent
 
pierre smith said:
One of the dealers for the "Supplenator [$3995:eek:] told me about a gentleman in Evans, Ga, 40 miles from me, who has built a RAT...Ram Air Turbine, that a lot of Military and airlines have as a standby. It folds out into the airstream and only runs when needed:

www.basicaircraft.com. He sells quite few to Stearman, J-3 Cub, Luscombe and others with no electrical system...$2195.

Best,
Click to expand...

Here's a picture of the RAT on 777, these actually are a hydralic pump which then drives an HMG (hydraulic motor generator).

rat.jpg
 
I have the SD-8 on my Bucker as the only and primary.

I dont have any avionics to speak of but I would suggest some quick calc's of your emergency buss loads and you could calculate your duration should the primary fail leaving you only the SD-8 and your battery.
The only issue I have is if I am flying a bunch of sorties, like for Young Eagles, or ride hopping, and going through a lot of starter cycles.
For back up purposes it would be a very good solution I would think, much better than another battery to maintain in my opinion.
Very good product.
 
Jon beat me to it, but I'd verify that the SD-8 can handle your loads in a true IFR situation. I think it would be marginal. If it's close then you would want to install an endurance bus so you don't have to remember what to switch off and what to switch on. On the Rocket, I went with the SD-20 but it requires a switch, controller, and the alternator (not cheap).

As I've said before, I'd go with two batteries but that's probably more changes than you want to make.
 
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Got one

Pierre, my 10 has the SD 8, and a second battery as well.

The SD 8 is dedicated to charging the second battery, A PC 680.

The main alternator is dedicated to charging the main battery, a 925.

The main battery feeds the main buss, and the aux buss through a big Shotkke diode.

The radios, and EFIS's are on the aux buss, everything else is on the main buss.

The way things work, the main alt can charge both batteries, but the SD 8 can only charge the aux.

The essential avionics -----radios and EFIS's will run from either buss, and will stay lit up if the main is shut down for an in flight problem/failure.

So far, the system is working very well.

I lite up the EFIS's prior to the engine start, so have oil pressure, and oil temp, and tach functions already running -----and due to the diode, the voltage on the aux buss does not see any sag from the starter, so the EFIS;s stay happy :)
 
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yikes

The SD-8 at under $500.00 is cheaper than the SD-20 and probably a lot cheaper than the 777 RAT.
 
SD20 with Z12 architecture

Z12 is basically the way to add a b/u alternator without adding a second battery or other stuff. The SD20 sits idle until it senses the bus down to 13V then it kicks into operation.

I chose the extra expense of the SD20 due to being IFR. I did not want having radios and pitot heat preventing me from getting someplace to get it fixed. Having the extra power makes main alt failure a non-event, and gives me more options

Note amperage ratings are based on a higher RPM than you might have on approach so have a loadshed plan accordingly. I also just learned that some spacers are required if you have an oil filter adapter.

Cheers
 
Ok, somebody needs to do the math for me...

...somebody smarter than me, which is most of you.
In a true emergency where you just want to get down at the next available spot, why would you need more than 8A alternator boosting a fully charged battery? I would think you would have more than enough juice to get a very reasonable range.
Now, if the goal is to continue to fly IFR on a complete back up system to your destination, well your one more failure away from a really bad situation.
Just curious.
 
I have had the SD-8 on the RV-8 since day one, and have no intention of removing it. However, I decided to star out without one on the -3 (although there is room for one later) because I have yet to actually use the thing on the -8 in flight - VFR or IFR. I grew up with unreliable alternators and poor batteries, so the standby seemed like a really great idea when I did the -8, and I was no longer restricted to "certified" installations. Then I added my Aux battery to alleviate voltage sags during engine start (that caused the EFIS to reboot), and that added a nice bit of redundancy.

What bothers me about the SD-8 in my installation is knowing that it is working. I used to test it before each flight by powering off the main alternator and brining the SD-8 on line. This proves it works. It also exposes us to the problem (with the internally regulated, automotive ND alternators) to damaging the voltage regulators on the main alternator. If you're using one of the expensive alternators that you know can be switched on and off with impunity while the engine is turning, then you're good to go - put in an SD-8, and test if before flight! Same thing if you don't believe that switching the ND alternator under load contributes to their early demise. I've gone 1000 hours on an ND alternator since I stopped switching it off/on with the engine running....just ONE data point!

I still think the SD-8 is a GREAT way to back up the electrical system, but it DOES weigh something, and batteries have gotten a lot more reliable. With the main and Aux batteries, I've got a good hour to get myself on the ground if the alternator fails. (No, it won't power Pitot heat - The RV stays on the ground if I have to fly through anything resembling icing conditions. We'd call that an "Operational Control of a Hazard" in my business - imposing a limitation rather than designing a fix for a remote case. )

Modern avionics (and lights!) draw so little power that using the battery as a backup is actually a pretty reasonable solution (especially with two of them). For our -3, we have P-Mags, which have their own power, so electrical power for the ignition is not an issue like it was for early EI engines. If I lose the alternator, I can power off the 430 and run on the G3X internal GPS's (two of them) for HOURS - plenty of time to find a way to safety.

But I am keeping the SD-8 in the -8....no reason not to, since it is already there!

(Pretty soon, avionics will be so low powered, you could go with an SD-20 as a primary....)

Paul
 
Looks like an SD-8...

..later in the year.

I also spoke with Skytec and they'll also have a backup alt. later this year.

Since money's kinda tight this time of year, fall will free up some.

Thanks guys,
 
I have the same setup that Nemo described,with wiring per Stein. It is stone simple and requires no brain power, switching or loss of equipment if the primary alternator goes TU.

The SD8 would have been borderline in my all electric -10, so I went with the SD20. It has it's own ext. regulator, which is set 1 volt lower than the primary regulator. If the primary alt. fails, battery voltage will start to decrease. When voltage has decreased 1 volt, the secondary regulator kicks in and the SD20 begins supplying the 'trons. No need for an endurance/essential buss, no switch sequence to remember, no need to terminate the flight prematurely.

Jim Berry
RV-10
 
Difference for me

The decision to land as soon a possible or land as soon as practical. I knew I wanted a backup alternator and I wanted to choose where I landed even if that was all the way to my destination. The extra expense and weight of the SD20 allowed me to have some more instruments, my 430W stays on with standby power, I don't want to have to rush for VFR weather if I am IFR.

Now if you take Paul's data point, this may just end up being a lot of dead weight and one might just decide an extra battery and all the internal backup batteries available make this all for naught. But if one night I am IFR and the alternator belt goes out, I sure will be glad when I just turn off the extra radio and continue to my destination on the SD20.

It is a roll of the dice as to if or when the back up will be needed with good maintenance of the primary maybe never.
 
Plane Power

Plane Power told me at Oshkosh they were working on a 20A gear mounted alternator meant to go on the vacuum pump pad, that would compete with the B&C. I keep bugging them, but the date keeps getting pushed out. Worth looking into as I don't think there's much to compete with the B&C for that size and type of alternator.
 
I have put the SD-8 on my last 3 airplanes. I really like the piece of mind it brings. I do check it once in a while, but not on every flight. I am running the B&C 60 AMP alternator and regulator, and they have proven themselves to be very reliable. I also change the alternator belt at less than the 500 hour recomended interval. At cruise power with all external lights off, the SD-8 will carry the IFR avionics load indefinitely. I also check the SD-8 for "play" every time the cowling is off, as way early on the drive couplings had a propensity to shear. They have since rectified that problem with a stronger coupling. I am running one mag and one Lightspeed ignition.

Vic
 
I have the SD-20. I check it from time to time. I can power most of my avionics easily with it if all of the lights are off. With the VP-200, if the main alternator goes TU, I get an alert with the voltage drop. VP attempts to bring the main alternator back on line for a few seconds. If that fails VP does an automatic load shed of the items I have programmed to shed and brings the SD-20 online. I can bring load shed items back on line if I desire to do so.
 
SD-8 story

I was flying VFR near Knoxville Tenn in Feb when the weather started to deteriorate. Just about the time I was starting to make a 180 degree turn and look for other options, my RV-8 began to accumulate ice. Not real thick, but clear, definite ice. I called center and told them I was reversing course, ran into icing and was beginning a descent. I turned my Pitot heat on and about 15 seconds later, I got a low voltage alarm. The GRT engine page showed I was putting out 0 amps from my alternator and my voltage was dropping rapidly through 11.5 v.
I have an SD-8 back-up with an essential and main buss via diode as described above. I turned my essential buss feed to EMER (fed directly from Battery and charged by SD-8) and turned on the SD-8 relay. With all my avionics working and my Pitot heat on, I was able to maintain right at 11.9-12.0 v as I made a precautionary landing at Knoxville Tenn. I had to descend through a 3000 ft thick cloud deck with the autopilot on.
I pulled the cowling and found that the plug on the back of the NipponDenso alternator was firmly in place, but the spade terminal had pulled back in the plug and was not making contact with the alternator.
The center guys were very helpful and stated that about 10 other aircraft also ran into unpredicted icing.
So, I would say that it functioned as planned, and as usual, under the worst possible conditions. I'm glad I had it.
I have dual elec ignitions, dual batteries, dual busses and dual alternators.

Bruce "FM" Edwards
RV-8 391FM
469 hours
 
This subject was debated long and hard by people going with the all electric Subaru engine operation.

The end consensus was operating with a single alternator and a back up battery made more sense than two alternators and one battery. The reason being, a shorted battery could deep six the entire electric system - 2 alternators would not help.

With one alternator and dual batteries, that could happen also but the batteries are isolated so a single battery failure would not as likely kill the entire system.

Of course the best system is like the old, old DC-9. Two completely independent electric systems.
 
David-aviator said:
a shorted battery could deep six the entire electric system - 2 alternators would not help.


Of course the best system is like the old, old DC-9. Two completely independent electric systems.
Click to expand...

Ya gotta draw the line somewhere. In-flight shorting of batteries is not high on my worry list, showing up sometime after spontaneous prop failure. One good alternator will provide power indefinitely. How long will your 2nd battery last and how do you know? You will need to have done a recent capacity test of the battery, know your electrical load, and add a safety factor. I read of alternator failures all the time on this list. Cant remember any in-flight battery shorts. I'll stick to my SD-8 with single battery.

Erich
 
erich weaver said:
Ya gotta draw the line somewhere. In-flight shorting of batteries is not high on my worry list, showing up sometime after spontaneous prop failure. One good alternator will provide power indefinitely. How long will your 2nd battery last and how do you know? You will need to have done a recent capacity test of the battery, know your electrical load, and add a safety factor. I read of alternator failures all the time on this list. Cant remember any in-flight battery shorts. I'll stick to my SD-8 with single battery.

Erich
Click to expand...

I agree, never seen or heard of a shorted battery bringing down an electrical system!
 
It can happen

Walt said:
I agree, never seen or heard of a shorted battery bringing down an electrical system!
Click to expand...

My hangar neighbor had a shorted Concord battery in a Maule. He said his radios started going out one by one and his ammeter was pegged out full charge. I was unable to charge the battery and it read 11 volts. A new battery and was well.

Paul Danclovic
Jamestown NC
RV-8A N181SB
 
pauldan181 said:
My hangar neighbor had a shorted Concord battery in a Maule. He said his radios started going out one by one and his ammeter was pegged out full charge. I was unable to charge the battery and it read 11 volts. A new battery and was well.
Click to expand...
How old was the battery? If you are reliant on the battery for safe completion of the flight, Bob Nuckolls recommends replacing it every two years.
 
pauldan181 said:
My hangar neighbor had a shorted Concord battery in a Maule. He said his radios started going out one by one and his ammeter was pegged out full charge. I was unable to charge the battery and it read 11 volts. A new battery and was well.

Paul Danclovic
Jamestown NC
RV-8A N181SB
Click to expand...

This sounds more like a single shorted cell which would indeed bring the system down to about 11 volts. The regulator is going to see this as a low battery and attempt to charge it at full current. However, most "modern" avionics will still keeping working at 11 volts so other than the high charging rate the electrical system is still basically functional just at the lower voltage.
 
Kevin Horton said:
How old was the battery? If you are reliant on the battery for safe completion of the flight, Bob Nuckolls recommends replacing it every two years.
Click to expand...

Despite the fact that many folks say the PC680 is good for 5+ years (which it probably is) I replace mine every 2-3 years just to be on the safe side. I have dual electronic ignition so I take good care of my electrical system :D
 
Shorted battery

IIRC he said the first symptom was noisy radio reception then he could receive but not transmit. Next ATC could not see his transponder. The battery was about 2 years old and lives under the cowl where heat probably shortened it's life.

My PC 680 was about 5 years old and had started cranking a little slow so I replace it a few monthe ago.

Paul Danclovic
Jamestown NC
RV-8A N181SB
 
Back to the question

My -9 is VFR only and over the years I have found planes just fine with no electrical system.

Thus, I don't have an E buss, back up battery, or standby alternator.

If I were flying IFR, I doubt I would change much as my Dynon has a battery backup and I would keep the 496, with its internal battery, as a backup. Maybe add a plug to one of the external antennas so I could plug in a handheld radio. But, fumbling for a radio while flying in the dark with limited electrics doesn't sound like much fun.
 
shorted battery

I had a battery short on a Jeep about 20 years ago. It took out the alternator and both high beams. The low beams and the radio were intact.
I'm installing a standby alternator. It will run a Dynon D180 w/ a battery backup on a seperate buss. The plane has a mag and an EI. At this point, I see the EFI as the weak link.
 
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N941WR said:
My -9 is VFR only and over the years I have found planes just fine with no electrical system.

Thus, I don't have an E buss, back up battery, or standby alternator.

If I were flying IFR, I doubt I would change much as my Dynon has a battery backup and I would keep the 496, with its internal battery, as a backup. Maybe add a plug to one of the external antennas so I could plug in a handheld radio. But, fumbling for a radio while flying in the dark with limited electrics doesn't sound like much fun.
Click to expand...

I am in your camp fire circle, Bill.

Been messing around with GA/Experimental flying for just about 40 years and have not had an alternator or a battery failure, guess its just dumb luck.

But that being said, I will not venture into IFR or night with one of these machines. If something can fail, it will and the backup solutions mentioned here are not much solace. The little accessory case alternator will conjure up significant pucker time before finding a place to land. And to muddle along with everything working as it should and wondering when and if it won't work doesn't sound like much fun. Life's too short as is and that kind of stress will shorten it more yet.

IFR flight can be enjoyable and relaxing in a properly equipped airplane - but it can not be so in a single engine airplane. There is no backup for the primary modus driving the prop and keeping things moving forward. It doesn't matter how many electric systems there are, the flight is a **** shoot. In the military all single engine operations are conducted attached to a parachute and the equipment is a lot better than anything here. Just because the FAR's render it legal doesn't mean it is smart. There's a lot of compromising going between Legality and Safety and SEL IFR.

When the clouds close in or the sun goes down, I much prefer to kick back and have a beer and try it another day than fight the IFR demons in an airplane not properly equipped for such flight.
 
Stand-by as the ONLY alt?

I'm a beta tester for Plane-Power with their new 30A vac pad alternator. To that end I have removed my other vac pad alternator (std RV type driven by a custom built vac pad belt drive unit). I can see that the PP unit puts out plenty of amps at normal RPMs, but it acts more like a generator in that it does not provide any usable amps below 1000RPM, or 1500 alternator RPM. I do see a higher amp reading when the engine is idling - I'm told this is the regulator trying to get the field to produce usable amps by hitting the field with more power.

So far, no problems with the drive coupling, which is the focus of this test.

The unit appears to be an ND clone, and is internally regulated @ 14.2v. Indeed, it shows exactly 14.2V in flight, and about the same amp load as the previous 60a unit did. A true stand-by unit will have the regulator set at a lower voltage level (13v or so?) and it will kick in automatically when the primary unit fails & voltage drops. Heck, that's easy enough for me to understand!

One of the things I wanted to change on my installation (TCM IO-550N) was the front mounted crankshaft-driven alternator - it is not a reliable unit, but at least it is heavy and expensive. :eek: I developed a drive unit and mount for a std ND alt for this engine, but I was waiting for a higher than 20a vac pad unit to be produced. Looks like that has happened, but the test is not quite finished up yet.

Plane Power will let you know when they are satisfied with the test units, and serial units are in production. These units take the belt system out of the failure question (several failure modes there) - another data point(s) for your safety calculations.

Carry on!
Mark
 
F1Boss said:
I can see that the PP unit puts out plenty of amps at normal RPMs, but it acts more like a generator in that it does not provide any usable amps below 1000RPM, or 1500 alternator RPM. Carry on! Mark
Click to expand...
All these accessory case alternators for Lycs will be low on total amps and/or low amps at idle. The physical space and gearing is such you can't turn it fast enough to make power at low RPM.

With that said there are aircraft wind driven alternators. Don't laugh, wind power is making domestic electrical power for a large part of the USA. Also a lot of planes had wind gens back in the day, some still do. Here is a modern example, STC'd for several aircraft.

http://www.basicaircraft.com/turbo-alternator-bpe-14.asp

It is only good for 6 amps and would be big drag, but if you were into the complicated you could have it retractable, pop-out as needed. The down side with planes today, even little RV's, is they are full lights, all electric panels. 6 amp would be dual electronic ignition. Personally I would go with the backup alternator, but I bring it up for grins. :D

Depending on your ignition and mission (day VFR, night low IFR) I think a good backup battery is all you need. If you lose an alternator you land. Most of us only have endurance of about 4 hours.
 
gmcjetpilot said:
All these accessory case alternators for Lycs will be low on total amps and/or low amps at idle. The physical space and gearing is such you can't turn it fast enough to make power at low RPM.

With that said there are aircraft wind driven alternators. Don't laugh, wind power is making domestic electrical power for a large part of the USA. Also a lot of planes had wind gens back in the day, some still do. Here is a modern example, STC'd for several aircraft.

http://www.basicaircraft.com/turbo-alternator-bpe-14.asp

It is only good for 6 amps and would be big drag, but if you were into the complicated you could have it retractable, pop-out as needed. The down side with planes today, even little RV's, is they are full lights, all electric panels. 6 amp would be dual electronic ignition. Personally I would go with the backup alternator, but I bring it up for grins. :D

Depending on your ignition and mission (day VFR, night low IFR) I think a good backup battery is all you need. If you lose an alternator you land. Most of us only have endurance of about 4 hours.
Click to expand...

GEORGE....WELCOME BACK - where have you been?!?! I know some have missed you! :)

Cheers,
Stein
 
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