Generator vs Alternator

[Nstarbf]

Morning All,

I was doing some pattern work yesterday and toward the end of the day noticed that my amp meter was on zero.  I was not able to get it to budge on any sort of ground testing.  My bird's now sitting in the hanger with the cowl off waiting for the A&P to do some tests on it Monday.  Depending on what he discovers, he suggested it may be an opportune time to swap out the generator for an alternator.  Any thoughts/advice?

Thanks in advance...

 

[Htwjr]

Not long after I got my C the generator broke and I replaced it with a Plane Power alternator.  I have been happy with it and it did save some weight but by the time I bought it and had it installed it was around $2000.  It is not a simple swap out as some modifications have to be done to the sheet metal as well as the wiring.  If I would have known the cost at the time I am not sure I would have made the same decision as the generator did fine for 50 years prior plus with LED lighting the load is less now.

[Jerry 5TJ]

A generator with a modern voltage regulator is much better than when paired with the original Delco voltage regulator.  The new regulator box installation is simple.  An alternator conversion is better yet, but it is an involved conversion.  

I elected to overhaul the generator and add the Zeftronics regulator to my C model.  

[carusoam]

If you have a couple of hundred bucks, or two amu...

If you are just trying to get by on this one, or this is your forever-plane....

 

+1 OH or swap Generator (aircraft Spruce) 

+1 Zeftronics controller

Start with the controller if the generator is still working.

The original controller is so stone simple, it just doesn’t work that well... adjusting the output correctly is a bit challenging...

New controllers come with LED outputs that can be wired to the instrument panel.  Nice to have a heads up when the charging system isn’t working as expected... bolt on, wire up... no adjustments...

My 65C got these updates back in the day... after a mis-adjusted sticks, stones and springs, voltage regulator melted all the solder out of the generator...

See if you can find a voltage vs. rpm chart for your generator... or a voltage indicator for your instrument panel to know when your system is charging or not... you may need 1700 rpm before a significant amount of juice is being generated... long time idling on the ground may be draining your battery, with the short burst of charging not covering the need...

Sometimes the load on the system is quite large... how many lights, radios, and coffee makers are you running in the cabin? Swapping the landing light for an LED unit may be helpful...

Then there is the storage of all these excess electrons... check the storage capacity of the battery, it may be getting low...

PP thoughts only, not a mechanic...

Best regards,

-a- 

[Yetti]

Replace the brushes in it and keep flying.

[chriscalandro]

Do the alternator. Yes you have to trim the metal on the baffle. Yes you have to change some wiring. I have a 67c and aside from taking the bottom cowl off and on the job itself can be done in a day by someone who knows what they're doing. 

I did mine myself "supervised" including the metal trim and the wiring in about a day and a half. 

The alternator is worlds better than the generator. With a low battery I can see 35-40 amps worth of charge at idle. 

Edited June 23, 2019 by chriscalandro

[Shadrach]

I am surprised the swap is $2k but things add up and removing the generator is a PITA.  I would swap but I’ve never felt at a loss for power. I have had a zeftronics VR for 15 years no issues and far better at maintaining consistent voltage. My system starts charging ~1050rpm. Alternator will save a few pounds and be easier to replace.

[DustinNwind]

As @Carusoam said; Alternator creates voltage no matter at what RPM setting. Generator you will usually only see it start charging above 1600 RPM depending on certain factors. If you're at an airport with long holds for IFR departures this becomes a problem with a large electrical load (full glass panel etc..) as you're idling while not charging. 

For most of us generator is plenty. Switch to a solid state regulator and overhaul the generator and it will work a long time. 

 

Not a mechanic though, that's ultimately who you should consult. 

[cliffy]

A couple of thoughts-

What is the amp rating of your generator? Has anyone ever done a load analysis to see if its capacity is in line with what your actual electrical requirements are? Has anyone ever added radios, etc to the airplane since new :-) You need to add up the "actual" amp needs of each electrical unit in your airplane (nav lites, landing light, beacon, each radio, panel lights, fuel pump, intercom, audio panel, etc) and see if all that exceeds about 80% of the rating of your generator, This is the actual running amperage of each item and not the circuit breaker rating. You can find the amperage of each usually on the manufacturers label. If in fact your load does exceed 80% of your generators capacity then it might be wise to look at a larger amp alternator.

If you are under 80%and you don't usually sit idling at low RPM with all the lights and radios on (and you have a good battery) then replacing brushes in the generator may be the cheapest way to go for a while or you could get it overhauled and run it for years. Check your log books to see when it was last overhauled. Just from time you might be better off with an overhaul rather than just brushes. Brushes wear down the commutator on the rotating part of the generator so after many years just replacing the brushes really doesn't work too well, especially if they have been replaced before.  

[Gary0747]

How often do you replace brushes on a 50 amp generator?

[carusoam]

I swapped mine out of the O360 once in a decade... about 1k hours...

they are extra long, so if the spring, guide, and commutator(?) surface... are all working appropriately, they last a predictably long time...

Pp thoughts as usual...

Best regards,

-a-

[Nstarbf]

Thanks much all.  I opted to have the generator re-built.  

[Shadrach]

On 6/23/2019 at 8:57 PM, cliffy said:

A couple of thoughts-

What is the amp rating of your generator? Has anyone ever done a load analysis to see if its capacity is in line with what your actual electrical requirements are? Has anyone ever added radios, etc to the airplane since new :-) You need to add up the "actual" amp needs of each electrical unit in your airplane (nav lites, landing light, beacon, each radio, panel lights, fuel pump, intercom, audio panel, etc) and see if all that exceeds about 80% of the rating of your generator, This is the actual running amperage of each item and not the circuit breaker rating. You can find the amperage of each usually on the manufacturers label. If in fact your load does exceed 80% of your generators capacity then it might be wise to look at a larger amp alternator.

If you are under 80%and you don't usually sit idling at low RPM with all the lights and radios on (and you have a good battery) then replacing brushes in the generator may be the cheapest way to go for a while or you could get it overhauled and run it for years. Check your log books to see when it was last overhauled. Just from time you might be better off with an overhaul rather than just brushes. Brushes wear down the commutator on the rotating part of the generator so after many years just replacing the brushes really doesn't work too well, especially if they have been replaced before.  

AFAIK all of the metal Mooneys were equipped with 50 amp Delco-Remy gens. I have never felt the need for more power and my generator is charging the system at 1100-1200ish RPM depending on load. I would think that the efficiency of modern avionics would leave most of us with higher capacity margins not less.

[RogueOne]

2 hours ago, Shadrach said:

AFAIK all of the metal Mooneys were equipped with 50 amp Delco-Remy gens. I have never felt the need for more power and my generator is charging the system at 1100-1200ish RPM depending on load. I would think that the efficiency of modern avionics would leave most of us with higher capacity margins not less.

Replacing OEM landing light with HID was huge as light has a large draw.  Offset (amp demand).  Replacing voltage regulator was also a huge positive impact on generator.  Mine comes on line at 1200RPM.  Just works.  No desire to change based on the quality of the function.

[Shadrach]

23 minutes ago, RogueOne said:

Replacing OEM landing light with HID was huge as light has a large draw.  Offset (amp demand).  Replacing voltage regulator was also a huge positive impact on generator.  Mine comes on line at 1200RPM.  Just works.  No desire to change based on the quality of the function.

Same. I’m running a zeftronics and a Xevision 50w HID. Even with the coffee grinder it’s charging at 1200rpm without it’s neutral at taxi power (1000rpm).

[Raymond J1]

Replacing the brushes is not enough. Sometimes it is also necessary to rectified the rotor inductance and corrected the irregular wear (on the following video, the defect after 2000 h).

Alternators age less well.

 

[cliffy]

Just turning the commutator is not enough  You still have to undercut the insulators between each commutator segment to be lower than the OD.   Fine hacksaw blades do it well

This is old school stuff that many A&Ps today have no idea of. 

[RLCarter]

25 minutes ago, cliffy said:

This is old school stuff that many A&Ps today have no idea of. 

A&Ps seem to send a lot of things off for repair, mags, carbs, generator/alternator 

[211º]

IIRC, you can remove the Cyl No. 1 exhaust pipe to provide space to remove the alternator instead of removing the lower cowl.