13.6V alt output?

Hi ya'll,

Does anyone around here know anything about the failure mode of ND internal regulated 60 amp alternators? I can ask on AeroElectric, but thought I'd poke around here first.

My alternator has started putting out a mere 13.6V. If I recall correctly the normal output of an automotive alternator is supposed to be 14.8V ish? This voltage is high enough that the battery is not draining, but not high enough to charge an Odessey PC680.

I'm not used to this 'low voltage' failure mode - kinda surprising.

I've checked that the belt is tight, contacts good - anything else I should check before taking the alternator off and trading it in on it's lifetime warantee?

Kevin

Actually, the typical charging voltage of an automotive system is 13.5-14.0 volts. It should never be over 15 for any reason, and anything over 14.5 is considered too high if it lasts for more than a few minutes. A 12V (12.6 actually) battery should charge just fine at 13.6. The big question is the amperage output. You can use a clamp on style ammeter on the output, or remove it and have it tested.

I'd take a close look at the battery first. If your battery can't supply enough voltage and current to the field windings, it can look like a bad alternator. Just fixed one of those this evening before leaving work. Battery that was less than a year old with a cell failing making it look like the charging system wasn't working. Max charging voltage was only 12.8 but the battery failed on the tester even though it had 12.4V-12.5V with no load or charge to it. After putting a new battery in, the charge voltage was back up to 13.8-13.9 which is right on spec for the car it was in.

FYI. Most newer internally regulated alternators won't charge much over 14.0 volts due to the sensitivity of the computer components in newer cars. 15.0V is enough of a spike to write off a weak component. I've seen electronic climate controls, transmission control modules and engine control modules killed by a voltage spike when jump starting. If you own a computer controlled car, always make sure you turn a load on in the car (lights, fan) before starting the car with the good battery. This will prevent about 99% of jump starting related electronics failures!

Engine ground strap(s)

Check your engine ground strap(s). Probably not part of the problem, but rule it out first.

)_( Dan
RV-7 N714D (716 hours)
http://www.rvproject.com

bearair said:

A 12V (12.6 actually) battery should charge just fine at 13.6.

Click to expand...

This may be true for a sealed lead-acid or gel-cell, but an RG battery like the Odessey neads a higher voltage to charge. The Odessey for example requires at least 14.2V.

Ref: http://www.odysseybatteries.com/files/techbook.pdf

Most internally regulated automotive alternators don't put out enough voltage to properly charge sealed RG batteries like the Odessey, which is one more reason not to use them.

OK George, your turn

had same problem

kevinh said:

Hi ya'll,

Does anyone around here know anything about the failure mode of ND internal regulated 60 amp alternators? I can ask on AeroElectric, but thought I'd poke around here first.

My alternator has started putting out a mere 13.6V. If I recall correctly the normal output of an automotive alternator is supposed to be 14.8V ish? This voltage is high enough that the battery is not draining, but not high enough to charge an Odessey PC680.

I'm not used to this 'low voltage' failure mode - kinda surprising.

I've checked that the belt is tight, contacts good - anything else I should check before taking the alternator off and trading it in on it's lifetime warantee?

Kevin

Click to expand...

Same problem this fall, except the voltage would wander from 12.2V to 13.3V. Checked the same items, no problems seen. Put in new alternator and life is good again at 14.3V.

Lifetime warantee? Ya mean I got a spare now?

Hmmmmm....

sprucemoose said:

Most internally regulated automotive alternators don't put out enough voltage to properly charge sealed RG batteries like the Odessey, which is one more reason not to use them.

Click to expand...

I guess I'll have to say then that the Oddyssey Battery is one incredible piece of equipment, since I have started my airplane with one at least 150 times in the past couple of months, and if my ND (internally regulated) alternator hasn't been charging it, that is one heck of a reserve capacity!

Hey, not trying to start a war or anything, but something doesn't sound right. Seriously, my ND alternator and Oddyssey battery system seem to be working great, and playing well together.

Paul

Charging voltage

Slightly off topic, but for those who use Vans's discrete voltage regulators and unregulated alternators, here's a tip that I'll pass along from George McNutt:

Mount the voltage regulator on the firewall, and drill a hole through the firewall to access the voltage adjustment screw from inside the cabin. I mounted a nut plate over this hole so that I can use a #8 screw to seal the hole.

Now, it's easy to adjust the charging voltage with the engine running with getting wacked in the behind with a Sensenich. Crawl under the panel, take out the screw, insert a small screwdriver and make the adjustment. Be sure to securely tie down the aircraft before you do this!

You can see the arrangement I used in the photos below. BTW, the bottom lug of the voltage regulator shares the mounting bolt for my main firewall ground. The top lug uses a nut plate mounted on the aft side of the firewall, and the visible nut plate is the one used for the adjustment screw. The adjustment potentiometer is recessed in the V.R., so the nut plate won't interfere with it.

Vern Little -9A. Panel in, planning first engine start next week.

Ironflight said:

Seriously, my ND alternator and Oddyssey battery system seem to be working great, and playing well together.

Click to expand...

What is the output voltage on your ND alternator?

Well, it is usually aout 14.2 - 14.3, of course - which is probably why I don't have any problems! So is your point that you shouldn't use internally regulated automotive alternators, or that you shouldn't use ones that don't put out at least 14.2 volts?

Sorry, I don't mean to be obtuse, I simply don't like absolutes. There are LOTS of airplanes flying around with these alternators that work great, and I really don't believe that they are accidents waiting to happen - any more than the old-fashioned, externally regulated Ford alternators in so many light planes. In the 23 years I owned my AA1B, I went through four of those alternators - two of them failed while I was IFR. Do I go around telling people not to buy them, or to throw them away if they have them? No - I tell them that no matter what you have, you should have a backup plan.

Of course, as you point out Jeff, we should probably wait for George's upcoming lengthy posting on the topic...

Paul

The point I was making, in my own obtuse way, was that RG batteries like the Odessey require a higher charging voltage than other battery types. I was responding to the post which said that the battery would charge OK at 13.6 V, which is incorrect. Of course, I couldn't resist the chance to get in a shot at internally regulated alternators. Come on George, where are ya?

Perhaps we should take this discussion over to the Aeroelectric List and let Bob have his say?

Peace Jeff!

I don't have enough time in my day to read the aerolectric list...

I think I shall simply retire from the field of battle, and go flying.....

Paul

Me too. It's made it into the 20s today, positively balmy around here.

You call this a battle? You really should spend some time on Aeroelectric list! Although from your reply, you obviously have!

Yes There Is A 13.6 Mode

What alternator do you have. If it has a remote voltage sense and it comes disconnected it will go the 13.6 volts. I am guessing because I have no idea what alternator you have, George

Check your wiring and make sure the IGN lead and S lead (if you have an S lead) is connected to a buss or battery source. It could be the regulatro, brushes, a who lot of things.

If you have a L connection I might suggest you use it. When you have "soft faults" where the alternator has an issue (like the remote sense lead becomes open or disconnected from a power source) the light will come on. The light is a great Hi/Lo volt light.

Many people just tie the IGN and "S" wire together to simplify wiring (not all ND alternators have a S wire). I personally think you would use the remote sense as designed, which is to the battery.

here is the trouble shooting tree for a Toyota but may apply\
http://www.autoshop101.com/forms/h8.pdf


Here is a wire diagram I made up (correction 5 amp to IGN wire may be 1 amp since the regulator only needs a small current unlike an external regulator.)
http://img519.imageshack.us/my.php?image=alternatorwiring2fh.jpg

George

Thanks all for the good advice (particularly that great Toyota document). I was able to start my investigation today, but got called away to the office.

I'll post a result once I can get back to the airplane - probably not till Tuesday.

I'm a glutton for punishment so i'll chime in,

I have the internally regulated alternator from vans and the odessey battery. My EIS consistently shows only 13.5v. I've been flying the plane since July. I was at first a little concerned about it but have had no problem starting the aircraft or any low voltage situations. I have a rather low demand electrical system though and haven't done much night flying but I do use the landing/taxi lights a lot near the airport for visualization purposes and have the strobes on constantly. I'm not sure if i would get to concerned about this unless i was planning to do long distance night IFR flying.

Doug Meloche

Odyssey Battery Needs 14.2 volts min

dmeloche said:

I'm a glutton for punishment so i'll chime in,

I have the internally regulated alternator from vans and the odyssey battery. My EIS consistently shows only 13.5v. Doug Meloche

Click to expand...

To deep charge a SLA/AGM battery it needs 14.2 volts min. (14.5 best) After full charge, 13.6 is good for trickle charge, but will not bring the battery up to full capacity if drained. 13.5 volts is too low, just my opinion, no arguing, if it works it works for you cool. George.

Upon further Review....

Eureka! If it hadn't been for this thread getting me to thinking (and a three-hour ride on Southwest this evening to give me the time...), I wouldn't have fiugred out what happened to me on my First Flight Day! this is the answer - and it proves that the Oddyessy wants more voltage for charging!

I used a nice workshop 40 Amp 12 volt power supply as ground power for the -8 throughout it's construction. I moved that out to the airport for final testing during assembly, and it still is connected to my ground power plug, and gets used in the hangar on occasion. For most of the construction, the ship's battery was not connected, and I only installed it when we started doing engine runs.

On the day of the first flight, I got out and powered things up about an hour early, using the external power supply (ironically, to "Save" the battery). When it came time to start and go fly, without the ground power connected, the engine wouldn't crank - the battery was low! (Long story short, we jump started from the truck, and had a good flight)

Now I realize that what is happening is that my power supply only puts out about 13.5 volts. That's fine for running things during test and checkout. But when the battery is in the system, even with the ground power enabled, I'm running off the battery - and the power supply is too low to bring it back up.

Good lesson, and good information from this thread!

Paul

Just an update:

Last night I finally had some time away from work to test and prod things. I tried the various good suggestions, but the fix (at least in my case) was to replace the alternator. All is well now - back at 14.2V.

When I originally installed the alternator I suspected that someone might have done the sleazy 'return something broken and claim unneeded' thing - it was a bit more bunged up than I expected a rebuilt alternator.

The replacement I just installed was new and shiny - perhaps my original alternator was not actually rebuilt but merely reboxed.

Kevin