Lyc 0-360 Alternator

Bissetg

Bissetg

Well-known member
I’m wondering if anyone can help me with an Alternator choice for my 0-360. From what I read the B&C L 40 could be a good option? An engineer friend of mine has suggested looking at automotive options.

I’m building a 4BQB kit so not too worried about having a little heavier Alt if that is the best solution. Any advice appreciated.
 
If you go with the automotive option, be sure to modify it so that you can fully shut it down in an overvoltage event, and install automatic protection to do that shut down for you. Neither of these features are common in off-the-shelf auto alternators. Otherwise you can damage your avionics faster than you can react. If you ever run a lithium battery, automatic overvoltage protection is a non-negotiable absolute requirement. Plane Power and B&C will both come with these features. B&C is externally regulated, which means more stuff to mount and connect, but it is easy to adjust and well supported. Durability and price are at the high end of the spectrum. Plane Power is internally regulated, but seem to sometimes last 300 hours. If you have a sparse electrical system and don't need redundancy, you might also investigate running an alternator off of the vacuum pad instead of up front. If you have important electric needs, you can run both.
 
I am going with the B&C vacuum pump driven alternator, save all that weight up front and a streamlined installation. Discussion with B&C today indicates an output of 35 amps at 2500 is to be expected. The same alternator mounting at the flywheel will delivery more amps because it is turning faster, actually 1.3 times faster. B&C's use an external regulator which is a better option than an internal regulator. Packaging that regulator inside the alternator is asking for a lot given the heat generated.
 
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If you choose a vacuum pad drive B&C alternator, be sure to review its AMP output at a given RPM on there "Quick Facts" data. The amp output at RPM's less than cruise drops off some. For example, one of them is a 20-40A alternator. On a Lycoming the output is 30A at 2500 engine rpm (Engine RPM x 1.3 = alternator RPM) but 25A at 2000 engine rpm. NO big deal if your electrical system is frugal, flying cross country. An hour in the traffic pattern with your seat heat turned on high might call for the belt driven unit. If you do run a vacuum pad driven alternator, some weight can be saved by installing a fly wheel without a belt drive groove.

Here is a link to an example. https://bandc.com/wp-content/uploads/2019/08/quickfacts_bc410-h_2019.pdf
 
If you want to run an auto alternator.... which all airplanes alternators are auto cores sometimes with lighter housing, better balancing and expensive paperwork... what you're looking for is a 1980 Honda civic alternator - they're usually 50A units. It's externally regulated, it spins the correct way, which is to the left looking straight on at it,(fan does, the alternator itself doesn't care), the mounting holes all line up to fit the lycoming brackets and it uses the standard 3/8" v groove belt. The pulley it will come with is a bit smaller than a standard aircraft alternator will, which you can swap for a larger one, or just leave it. It won't get over it's max rpm, but it'll make a lot of amps at very low engine speed(I like that). Plus auto alternators almost always come with a lifetime warranty. Aircraft alternators, it's too bad that thing only lasted 1 year. Pay me another $800.

On the regulator I do run the B&C 12v because it has the over voltage built into it. You could use any $15 solid state regulator and build your own crowbar circuit for another couple dollars if you were so inclined though.
 
I had an auto specialty shop that i closed about 13 years ago, but still mess around a bit. The rebuilt stuff coming out of the auto parts stores is horrific in quality, although if you don't mind spending time swapping parts all the time, they do come with a good warranty. My understanding is that is currently still the case, and the local, very large electric shop that has rebuilt starters, alternators, etc stopped rebuilding alternators several years ago. They have been in business over 50 years. The only regulators they could source were either bad out of the box(most of them), or within a year. They were losing money on returns. I think Van's has a good source for auto alternators, but I would still convert it to an external regulator.

I think the pad mount alternators put out very little power at idle, but if you aren't using a lot, it is an elegant solution. I would be draining my battery at idle.

VAF has a long thread titled "Alternator reliability poss". Good reading, and hundreds of real world numbers for comparison.
 
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My $40 auto alternator has at this point lasted longer than the 2 plane power's I had in the past. Swapping parts all the time, IMO, is not unique to cheaply rebuilt stuff, but rather common on really expensive aircraft stuff to. Probably because they're overhauled right next to each other and one gets a sticker while the other doesn't.

Also, there are auto alternators that don't need to be converted to external. I have no idea why you'd buy one that needed that when you don't have to. Especially when the externally regulated alternators are cheaper.
 
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I'm running the 60 amp B&C and haven't had any issues. An added bonus is that it is about 2/3 the size and weight of the old alternator that was mounted on my engine when I got it for a core.
 
Thanks very much guys, this stuff is very helpful. I’ll do some homework on the options this week. My build is very basic so not much in terms of electrical load.
 
B&C alternators are not cheap but seem to be very reliable. Sounds like the 40 amp belt drive would be plenty for you, and as mentioned check out the vacuum pad driven models also. Plane Power alternators don't seem to have a good record of reliability.
 
I did not know there were any small frame auto alternators with external regulators, but my most of my auto experience is with just a few manufacturers.
 
As I side not I talked to a couple of different reps from B&C and they were quite open and transparent. Prior to their new line of pad mounted alternators, they said that belt driven alternators have proven to be more reliable than pad mounted, gear driven ones. Their opinion, not mine.

But with their new pad mounted alternator at about 5 pounds, I may end up with 2 alternators and 1 battery. Almost the same weight as 1 alternator and 2 lithium batteries, but a bit better redundancy. I will still carry a lithium jump pack in my tool kit.
 
alaskabearhawk said:
Bob Nuckolls AeroElectric Connection web site is a treasure trove of information on this and many other subjects specific to experimental aircraft: http://www.aeroelectric.com/articles.html
Click to expand...

I am a student of the Nuckolls AeroElectric book/methods. B and C seems to partner with him, or at least provide materials that align with all of his EAB electrical system practices. He also has a forum is quite accessible. see the Aeroelectric List on Matronics. http://forum.matronics.com His methods produce a well thought out, highly reliable, light and inexpensive electrical system. (Seems to me I might be a little biased.)
 
I have a questions about wiring a 60 amp BC Alternator for an O-360. Some schematics show single Alt-Field breaker (5 amp) with Alt-Sensor terminal getting power from Alt-Field terminal (jumper wire), while other schematics show separate breaker (2 amp) for the Alt-Sensor. Any advice or guidance is appreciated.
 
I installed a different B and C alternator and regulator in my aircraft. B and C has diagrams to show installation of the system. The link below is to B and C's reference library for the hardware they produce. Look for your regulator under Installation instructions and also wiring diagrams. In my build I considered them authoritative.

https://bandc.com/reference-library/
 
BrokenStraw,

You may have already gotten all the answer you wanted from the link that Brooks provided, but the B&C published info will always show using two circuit breakers to the regulator, one 5A for the field current and a 2A for the voltage sense input. The voltage sense input also keeps the low-voltage warning output working if the 5A breaker opens which it will if the over-voltage protection decides to step in. Some people have installed it using a single circuit breaker and jumpered the field supply input and the voltage sense input together. There are two downsides to doing this so you should understand those if you are considering doing that.

1. Having a second sense input that draws very little current (the 2A breaker) enables the regulator to accurately sense the bus voltage even if that path develops some resistance over the life of the aircraft. The split rocker switches used for battery/alternator master switches are notorious for developing some resistance through the contacts as the switch ages. If the two regulator inputs are jumpered together and powered through a single 5A circuit breaker and through the alternator switch, the resistance of the circuit will cause a voltage drop at the regulator input and since the field current varies, the amount of voltage drop varies. This causes the voltage regulator to see an inaccurate and sometimes varying voltage which results in a less stable bus voltage. So if you are willing to accept an increased risk of poor regulator performance and required maintenance down the road, the single circuit breaker option might be considered.

2. The over-voltage protection works by intentionally faulting the field supply input to ground which causes the 5A circuit breaker to open. The alternator will no longer be online and the bus voltage will drop. The B&C regulator provides an output terminal to drive a low voltage warning light which would provide an annunciation to the pilot that something is amiss. If the two inputs to the regulator are jumpered together from a single breaker, then the OV event that opens the breaker will also disable the low-voltage warning. This would not be acceptable if you are counting on the low-voltage warning from the regulator. However, if you have an EFIS or engine monitor that is providing a low-voltage warning independent of the B&C regulator, this is no longer a factor.

Another option that I'll mention is the new Silver-Flite series of alternators that B&C is introducing. These are internally regulated with built in over-voltage protection and will require only a single breaker feeding an alternator switch which then goes to the small alternator connector to turn it on or off. There is no output provided for low-voltage warning or alternator failure annunciation so you would need to rely on an independent means of low-voltage warning to detect alternator failure. The 60A belt driven unit has begun to ship and the 40A belt driven and 30A pad mounted units should begin shipping the end of March. These Silver-Flite units are a little less expensive than the traditional B&C units but when you consider that you don't have to purchase a regulator, the savings becomes much greater.

David Swartzendruber
Bearhawk LSA builder (nights and weekends)
Engineer at B&C (during the workday)
 
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