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B&C Alternator + Backup

bkervaski

Hellloooooooo!
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I went to watch a buddy of mine fire up his RV-10 for the first time and noticed that he didn't have a second field switch for his B&C backup alternator .. instead, there was a "hall sensor" in place to automatically switch to the backup.

I may swap my PP for this B&C+Backup alternator setup, any feedback on this type of install?

Can the regulators be installed on the hot side of the firewall?

Thanks for any advice :)
 
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I went to watch a buddy of mine fire up his RV-10 for the first time and noticed that he didn't have a second field switch for his B&C backup alternator .. instead, there was a "hall sensor" in place to automatically switch to the backup.

I may swap my PP for this B&C+Backup alternator setup, any feedback on this type of install?

Does this take two regulators? If so, can the regulators be installed on the hot side of the firewall?

You don't need a field switch for the backup alternator, though their wiring diagram shows one. I installed the switch on my RV-7, my neighbor doesn't have one on his RV-14.

Installation instructions state that regulators (one for each alternator) must be installed on the cold side of the firewall.

The set voltage for the backup alternator is purposely adjusted lower (13 volts instead of 14-ish). The backup alternator coasts until the buss voltage reaches the lower value.

With the Hall sensor you get a fancy light warning light that glows steady once the backup alternator turns on, and starts blinking if the current draw is greater than what the backup alternator can put out. The sensor does not however turn on the backup regulator.

I've had mine come on once, when the B lead terminal on my primary alternator cable broke at the alternator due to a certain- ahem- error. Beings as my RV-7 has dual electronic ignitions, I was suddenly glad to have it.
 
With the Hall sensor you get a fancy light warning light that glows steady once the backup alternator turns on, and starts blinking if the current draw is greater than what the backup alternator can put out. The sensor does not however turn on the backup regulator.

Hmm. So how are you enabling the backup regulator? With a switch?

I've built some regulators for RC so this might be an ignorant question as I'm sure the aviation regulators are far more advanced, but if the voltage goes low on the primary alternator, and the backup is enabled by the hall sensor, why would you need a separate regulator just for the backup?
 
https://bandc.com/product/standby-alternator-controller-installation-kit-homebuilt/

"If the primary alternator fails in flight, the SB1B-14 controller will sense the drop in system voltage and automatically activate the standby alternator."

I have this setup in my -14.BC460-H primary and BC410-H stby with LR3D-14 (primary) and SB1B-14 (stby) controllers. The controller/regulators should be mounted on the cool side of the firewall.

I have a single ALT field switch on the panel for the primary alternator, but have dedicated circuit breakers for both.

-Rick
 
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Hmm. So how are you enabling the backup regulator? With a switch?

I've built some regulators for RC so this might be an ignorant question as I'm sure the aviation regulators are far more advanced, but if the voltage goes low on the primary alternator, and the backup is enabled by the hall sensor, why would you need a separate regulator just for the backup?

Yes, I am enabling the backup field with a switch, but strictly speaking it's unnecessary. See also Rick's reply. That enables the regulator but doesn't turn on the alternator.

B&C's architecture for this requires two regulators, one for each. Again, the set voltage on the backup regulator is set lower than the primary, so the backup doesn't come on until the buss voltage drops to the backup regulator's set level. The Hall sensor does not turn on the backup. Its purpose is only for the (optional) warning light logic.
 
The operation is just as described above.

However, the B&C alternators are so reliable that the backup alternator may never become in use unless "- ahem- error" :)

But in case if it happened, it is nice to have a backup that is just as reliable.
 
The operation is just as described above.

However, the B&C alternators are so reliable that the backup alternator may never become in use unless "- ahem- error" :)

But in case if it happened, it is nice to have a backup that is just as reliable.

Primary alternator reliability is only half the equation...the belt being an equally critical component.
 
The set voltage for the backup alternator is purposely adjusted lower (13 volts instead of 14-ish). The backup alternator coasts until the buss voltage reaches the lower value.

a permanent magnet alternator (e.g. SD-8) doesn't coast. It takes the same amount of energy to rotate the alt regardless of the amount of wattage it is supplying via that regulator (it just throws away excess energy below that required to reach the set voltage). The output will vary, depending upon the regulator request, but this doen't change the rotational load required to spin the alt. This is different than a std alternator, where the output, is determined by the current delivered to the alt's field circuit and driven load is proportional to the output wattage.

Letting the b/u alternator deliver full power and supplement via the main alternator would create less parasitic HP loss from your engine, as the HP required for the b/u is static and variable for the main.

Larry
 
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Hmm. So how are you enabling the backup regulator? With a switch?

I've built some regulators for RC so this might be an ignorant question as I'm sure the aviation regulators are far more advanced, but if the voltage goes low on the primary alternator, and the backup is enabled by the hall sensor, why would you need a separate regulator just for the backup?

The hall sensor is a red herring in this discussion - the regulators do all the work. Both regulators are energized at all times. Since the primary regulator is set to a higher point than the secondary, it drives the primary alt to a high enough voltage that the standby regulator takes its alt offline.

Everything remains in this state unless the primary alt fails for whatever reason. At that point bus voltage begins to drop to what the battery can provide. When it falls below the set point of the standby regulator, it dutifully wakes up the standby alt.

This is the architecture I'm planning for my -8. I really like that there's no action required by the pilot to activate the standby in case of a failure. Fewer manual tasks to execute means fewer things to potentially screw up.
 
a permanent magnet alternator (e.g. SD-8) doesn't coast. It takes the same amount of energy to rotate the alt regardless of the amount of wattage it is supplying via that regulator (it just throws away excess energy below that required to reach the set voltage). The output will vary, depending upon the regulator request, but this doen't change the rotational load required to spin the alt. This is different than a std alternator, where the output, is determined by the current delivered to the alt's field circuit and driven load is proportional to the output wattage.

Letting the b/u alternator deliver full power and supplement via the main alternator would create less parasitic HP loss from your engine, as the HP required for the b/u is static and variable for the main.

Larry

True enough. But the BC410-H alternator in question is not a permanent magnet alternator. Different animal.
 
The hall sensor is a red herring in this discussion - the regulators do all the work. Both regulators are energized at all times. Since the primary regulator is set to a higher point than the secondary, it drives the primary alt to a high enough voltage that the standby regulator takes its alt offline.

Everything remains in this state unless the primary alt fails for whatever reason. At that point bus voltage begins to drop to what the battery can provide. When it falls below the set point of the standby regulator, it dutifully wakes up the standby alt.

This is the architecture I'm planning for my -8. I really like that there's no action required by the pilot to activate the standby in case of a failure. Fewer manual tasks to execute means fewer things to potentially screw up.

What he said.
 
a permanent magnet alternator (e.g. SD-8) doesn't coast. It takes the same amount of energy to rotate the alt regardless of the amount of wattage it is supplying via that regulator (it just throws away excess energy below that required to reach the set voltage). The output will vary, depending upon the regulator request, but this doen't change the rotational load required to spin the alt. This is different than a std alternator, where the output, is determined by the current delivered to the alt's field circuit and driven load is proportional to the output wattage.

Letting the b/u alternator deliver full power and supplement via the main alternator would create less parasitic HP loss from your engine, as the HP required for the b/u is static and variable for the main.

Larry

I'm pretty sure that is not the case with a PM generator (or any generator for that matter), as the load increase the torque required to turn the generator will also increase.
 
I'm pretty sure that is not the case with a PM generator (or any generator for that matter), as the load increase the torque required to turn the generator will also increase.

I will defer to those more experienced. I have certainly seen the behavior you mention with my home AC generator, but thought that these type of devices were different (they have a governor to increase torque to maintain RPM). I just don't see how they could be influenced by load, as they are pure output, with no feedback, based upon the magnetic field and the resistance it creates. I understand that the voltage output drops, at a constant RPM, as the load increases but did not understand the load on the engine increased to maintain that RPM.

Larry
 
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A couple of thoughts: When I recently went with a stand by alternator for my dual electronic ignition RV-8, I did add the light indicator. It gives me a heads up to see what, if anything, I might want to take off line and as a reminder to keep RPMs up since the power the b/u is able to produce is related to engine RPM. Both are B&C with primary reg. in front of firewall but b/u reg up high in front baggage compartment.
 
A couple of thoughts: When I recently went with a stand by alternator for my dual electronic ignition RV-8, I did add the light indicator. It gives me a heads up to see what, if anything, I might want to take off line and as a reminder to keep RPMs up since the power the b/u is able to produce is related to engine RPM. Both are B&C with primary reg. in front of firewall but b/u reg up high in front baggage compartment.

This is also an aspect of my system plan. The B&C SB1B-14 regulator includes a pin to activate a warning light when the standby alternator is awake. I'll be connecting that to a contact input on the Dynon EMS, and setting it up to be a nice blatant alert if the standby ever comes on line.
 
This is also an aspect of my system plan. The B&C SB1B-14 regulator includes a pin to activate a warning light when the standby alternator is awake. I'll be connecting that to a contact input on the Dynon EMS, and setting it up to be a nice blatant alert if the standby ever comes on line.

That may or may not work when the reg output is connected to a high impedance input, I know the output generally will not work when connected to an LED in place of a std bulb.

With the stby output set to a lower voltage than the primary its pretty easy to set up yellow/green ranges to indicate the lower voltage suppled by the BU system.
 
SD-8

Reviving this thread with a question as I’m about to add a backup alternator for my 14.
Would a SD-8 be worthwhile as backup if the goal is just to get you back you your home field. Looks like it’s lighter and would provide 8 amps to run enough basic equipment or is that shortsighted and it’s better to just get the B&C and have what looks like 20 amps.
Just curious what others have done.
 
My B&C 410H alternator will deliver enough power to not need the primary alternator in most conditions of flight. If I turn on all the lights, and the pitot heat and the panel at its brightest, etc I can overdo it. But for most ops it is plenty and I wouldn't have a problem relying on it. I have turned on every thing on my plane and didn't discharge my battery (was testing current flows to confirm); but if it was cold enough the pitot/lights could get there maybe.

The 410H doesn't have much overhead to recharge the battery after a start so I would use it solo carefully.

I did configure a switch for the backup alternator field, and I turn it on when I turn on the primary alternator. The backup alternator controller is on a breaker. If I wanted it off for any reason I can do it. It isn't strictly necessary but I like it.
 
True enough. But the BC410-H alternator in question is not a permanent magnet alternator. Different animal.

NOT TRUE ENOUGH. That the SD-8 is a PM alternator simply means that it does not need field current to generate output, the magnetic field needed is provided by the permanent magnets. The regulator for the SD-8 performs an entirely different job - instead of feeding the alternator field current, it provides phase controlled rectification of the alternator AC output, much like the operation of a lamp dimmer. That means when no output is required, the alternator in fact totally idles, there is no such thing here as "throwing away" the power - power is simply not generated, just like there is none drawn from an outlet with nothing plugged in. An SD-8 therefore DOES NOT take the same amount of power from the engine under all conditions.

That said, 8 amps in most of our planes now is insufficient backup anyway, so in most applications the SD-8 is not a good BU solution.

BTW, in 1400+ hours, the only system failures I have had have been alternator related. One vibration broken field wire (In IFR conditions) and one abrasion field wire intermittent short, leading to transient field breaker trips. This speaks to a couple of topics in this thread - backup IS quite valuable, alternator (related) failures do happen, and in my case, it was never the B&C alternator itself! I have the 20A B&C BU with automatic second regulator pickup, and it works perfectly, has gotten me once home across the country with one of the primary failures.
 
My 2¢

My 2¢:

Connecting the B&C wound-field standby alternator's regulator directly to the main bus will result in the battery supplying full field current of ~3A to the field with the engine off, which will drain the battery and heat the alternator. Also, in a fire in the cockpit scenario, one would not be able to turn the standby alternator off.

The latest incarnation of the B&C main regulator, LR3D, will operate an LED lamp without modification. The legacy LR3C main regulator and the SB1B standby regulator will drive an LED if the LED is paralleled with a 470 ohm resistor. I imagine this resistor will allow an EFIS input to be used also. Ref http://aeroelectric.com/Pictures/Schematics/LR3_LV_Led_1.jpg

Bob Nuckolls recommends using an LR3 regulator for both the main and standby alternators. The standby alternator with its hall-effect load sensor and panel light indicating it is supplying field current was for the STC market. An EFIS will tell you the main alternator is off-line when the voltage drops below its setpoint, and the standby alternator will tell you when it's overloaded when its voltage starts to sag. Ref what Bob Nuckolls says about the SB1 regulator on Sept 24, 2018 here: https://docs.google.com/document/d/1LXf85fj9AgdscGI49XYVu2yMUeSeH8FUmTIG2pARI1E/edit

The alternator formerly known as SD-20 (SD-20 is a bit heavier and uses slightly different attach hardware), B&C's BC410 is actully a 32 A alternator on Lycoming engines at cruise RPM which means the 20 A warning light of the SB1B regulator is misleading. The main advantage of the larger BC 462 is more current at low RPM.

Ref https://vansairforce.net/community/showpost.php?p=1581613&postcount=21

For an SLA battery the standby alternator might better be set to 13.5V versus 13.0 to ensure full charge without loading the alternator very much, or overheating a discharged battery. I imagine you could jump start and takeoff with a discharged battery with the main alternator off and the backup alternator on and not overheat the battery but you heard that from some guy on the internet.
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NOT TRUE ENOUGH. That the SD-8 is a PM alternator simply means that it does not need field current to generate output, the magnetic field needed is provided by the permanent magnets. The regulator for the SD-8 performs an entirely different job - instead of feeding the alternator field current, it provides phase controlled rectification of the alternator AC output, much like the operation of a lamp dimmer. That means when no output is required, the alternator in fact totally idles, there is no such thing here as "throwing away" the power - power is simply not generated, just like there is none drawn from an outlet with nothing plugged in. An SD-8 therefore DOES NOT take the same amount of power from the engine under all conditions.

There’s a nice simple physical picture to see why the more power the alternator supplies, the more power it takes from the engine to turn it, regardless of whether it uses a field coil or a permanent magnet. When no current is drawn, it’s easy to spin the alternator; you need only overcome whatever friction there is in the bearings. But as you start to draw current, this causes the alternator’s primary coils to act as electromagnets - and their magnetic field and the field from the field coil or PM oppose each other, making it harder to turn the alternator. The more current you draw, the stronger the magnetic field, the harder it is to turn. You can calculate the engine power needed to turn the alternator: it’s equal to the electrical power generated, plus a little for the frictional heating in the bearings, plus a little for the heat generated by the regulator.
 
The way permanent-magnet alternator regulators work is by opening the
alternator's output with a solid-state switch for part of the AC sinewave.
 
Installation instructions state that regulators (one for each alternator) must be installed on the cold side of the firewall.

I'm curious what instructions you are referencing.

I'm installing a LR3D-14 and those instructions have the "preferred" location is the pilot side of the firewall. Page 7/Secion B step 3
https://bandc.com/wp-content/uploads/2020/05/LR3D-Technical-Manual_RevIR_5-13-20.pdf

Interestingly, the AVC1 has the "preferred" location is on the *forward* side of the firewall. Page 8/Section C Step 3. Using "Pilot or Engine" side would be clearer, IMO, but I take "forward side" to mean engine side.
https://bandc.com/wp-content/uploads/2020/03/AVC1_Technical_Manual_RevIR_3-11-20.pdf

I called B&C to discuss the mounting location since in the RV8, locating the regulator in the luggage area or behind the instrument panel was not desirable for my situation. They said it was most important to mount these with the terminals down with a drip loop to prevent water damage, and mounting on the engine side of the firewall was fine.
 
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