sizzling hot new alternator

[Bobg]

Just installed a new Mondo alternator with a internal regulator from Blue Circle, before installation, I changed the #10 output wire from the switch to a Positive Buss bolt, which is connected to the starter solenoid. (after I did a harness upgrade) at the engine instrument panel.

My new Alternator got so hot I can smell it, and the case will sizzle water,  I am thinking it is because  the battery voltage is down in the 11.3-5 area after a weekend,  and it is working so hard, I don't remember this happening when I had my motorala 55 in.I have 4 T105's, I'm thinking  I will have to replace the batteries as they are 5 years old and even on shore power charging, I can't get them above 12.10-20, and maybe that is the whole problem. or maybe I need a bigger wire from the output on the Alt.

But will the Alternator get so hot it will destroy itself by trying to charge 4 discharged  Golf cart batteries?  Ironically even at 11.3-5 volts, measured with a DVM at the batteries, my engine will spin right over and start.

I have checked the archives and some say they like the heat coming out of the head door, so maybe it is normal that hot,  I don't think so though any advice,  Thanks guys

[Stu Jackson]

Bob, you're right.  Attempting to charge a depleted house bank with an alternator will do that.  Alternators are good for maintaining the house bank between 50% and 80 to 85% of charge.  The reason you old alternator didn't do that was because it was a tapering charger on a relatively small alternator not made for charging larger house banks, and that after it started up didn't do too much, although Maine Sail contends that old internal chargers will do just fine in that range.  You neglected to mention the size of your new alternator.  That #10 wire was dangerous.  Please move your alternator output directly to your house bank --- we've discussed this a number of times ---  Reply #11 here: http://c34.org/bbs/index.php/topic,4949.0.html   I don't understand your positive buss bolt description, can you elaborate a bit as to exactly how it's wired?  With a seriously depleted bank, whatever your charging source is, you're gonna work it overtime.  Maine Sail discussed this in a topic on the C36 site just today: see: http://www.c36ia.com/forums/showthread.php?t=806  Internal regulators do not allow the Small Engine Mode that I documented here, available with external regulators, nor do they allow battery or alternator temperature sensors.  If it was my boat, I'd carefully check the batteries with a hydrometer for condition, charge them fully with a shorepower charger, and then rewire it properly:  AO to house bank, C post of 1-2-B switch to starter solenoid.  That "heat out of the head door" was a joke by Randy.  So was #10 wire in a charging circuit.

[mainesail]

Maine Sail contends that old internal chargers will do just fine in that range.  

Stu,

This is only if the internal regulator set point is above 14v. Some of the older regulators were factory set as low as 13.6 - 13.8 which makes the last 20% take a very long time compared to an alt delivering a higher voltage.. The dumb regulator I use has adjustable voltage output and can be bolted directly to an older Motorola style case if you have one of the old 13.6 v regulators. Today most dumb regs ship at 14.2-14.4 volts output..

There is a little white screw that lets you adjust the output voltage set point.



From roughly 50% to 80% SOC, the battery use range we should be in for cruising, even a regulator set at 13.6 will perform nearly identically to an external regulator it's the last 20% that will take forever with a low voltage output set point, up the set point and it will charge the last 20% with no issues..

I suspect the Bob has a bad cell if he can't get the voltage up above 12.1 even on a shore power charger but the charger could also be the culprit. I would check the cells with a hydrometer firts as you suggested..

[Bobg]

Stu, thanks for your reply, I have a Mondo (exact bolt on) from Blue circle, it is a 50 amp internally regulated alternator, the blue circle shop is only 30 miles from me.  the positive buss bolt was a add on by me as I needed more room on the  starter solenoid bolt.  I ran a #4 wire from the starter solenoid bolt to the new + bolt. which is fastened by the small door by the AO

The wire that came out of the previous alternator output went to the switch, (a 10 or 12 gauge orange wire) and back to the starter solenoid.  I shortened that OEM wire  and connected it to the starter solenoid.  I am a little confused, you mentioned that #10 wire was dangerous, I think It is what OEM had in there, albiet through the switch.  did you mean it becomes dangerous when it is shortened and ran directly to the starter solenoid?

Here is where it gets a little confusing to me, If I run a Alt output wire directly to the house batteries, do I come off the output post on the Alt with a #4 wire, and snake it to the house bank under the floor sole and connect it one of the house  batteries?

And do I run a new #4 wire from the C Post on the battery selector switch to the starter solenoid as per your Fig 3 drawing

In any event, I better check my batteries over real good with a hydrometer before I fry my Alternator.  With new T105's fully charged. i'm thinking connected in series, they should read around 12.8 volts,

Thanks guys, bear with me please, I do have a dedicated starter battery behind the engine, and a battery combiner.

Bob

[Randy and Mary Davison]

Bob,

It does sound like you might have a bad battery cell or charger problem.  12.1V is too low.  I also have 4 T105s and after two full days at anchor and down 145AH they are at about 12.4V.

It's also true that your alternator will get very hot charging a depleted house bank.  I panicked a few months after installing my Ample alternator because it, too, would sizzle water.  Ample told to me to quite worrying - that the alternator was designed to run that hot.  THat was many years ago and all is still well.  Heat out door was not entirely a joke as per Stu.  I'd never advocate a dangerous practice like warming your hands in front of that open door but when you start out on a cold, wet morning down 225 AH, and can get the Admiral to steer, well, you know...sorry Stu couldn't resist.

Randy

[Bobg]

thank you Randy, I just bought 4 new 105s and will install tomorrow, will run a new wire directly to one of the battery banks, and use a dvm to see if both banks are being charged, , and check out my 12B switch and see about running a wire to the solinoid from the C post, I believe that is what is being suggested by Stu, thanks again guys   Bob

[Stu Jackson]

Bob, I think you understand it now.  You should already have a #4 wire from the C post of the 1-2-B switch to the {alternator starter solenoid} location.  I simply don't know how you were wired originally, but that #4 should go to the starter solenoid, and the new #2 AO to your house bank per Figure 3.

[waterdog]

Do not forget to include a fuse in the circuit on directly wiring to the house bank.   Otherwise you have a hot wire in a high vibration environment.   If the bolts on the alternator come undone or the wire chafes you'll have near unlimited energy welding your engine in new and interesting ways before it burns your boat to the waterline.   I even go so far as to wrap the handles of wrenches in electrical tape if I work these connections live.   

[Stu Jackson]

Steve's experience with his runaway alternator has led me to recommend placing the fuse inline with a circuit breaker, Blue Seas Series 187 looks like it will work.

While you're at it, you should do a wiring diagram BEFORE you make any changes.  If you do that, you'll begin to understand the system MUCH better.  See the diagrams here:  http://c34.org/bbs/index.php/topic,4949.0.html, which I'd previously linked, Reply #12 has a great simplified overall diagram.  

[Ron Hill]

Guys : On a related item for the alternator, you should consider using a self locking nut on the output stud rather than a nut and lock washer.  A thought

[mainesail]

Guys : On a related item for the alternator, you should consider using a self locking nut on the output stud rather than a nut and lock washer.  A thought

Ron,

I love nylocs but ever since having melted the "loc" part of one, and subsequently had the nut get loose, on a hot engine component, I stopped using them on items that can very get hot. I still use lock washers on alt outputs and have never had one come loose. An alt post should not, key words "should not", get that hot but if you really ran it hard it could potentially get to the upper limits of the safe working range of a Nyloc which is about 280F....

[waterdog]

Ron,

I love nylocs but ever since having melted the "loc" part of one, and subsequently had the nut get loose, I stopped using them on items that can get hot. I still use lock washers on alt outputs and have never had one come loose. I doubt an alt post would get that hot but just a thought...

I had an alternator fail as the insulation around the post melted and it arced and sparked.   A nyloc on the post would certainly have melted.   I  now use a lock washer and a second nut to lock on the alternator post.   

[Bobg]

OK, little update, I have installed 4 brand new T105's, ran a #6 wire from the output on the alternator to the house bank battery.  The starter solenoid wire ran from the C post, or the All post on my selector.  one set of 2 Trojans is connected to the 1 position and the other set is on the #2 position, I fully charged the new set of house batterys with the shore power charger, then went out with the boat, the next morning, after being on the hook, I started the engine and after about 45 minutes at 2000 rpm, smoke started coming out from the engine compartment, the new alternator was so hot it locked up and the belt started to slip.

I couldn't turn it with a bar, after cooling about 1/2 hour I could spin the alternator, started the motor and went to the slip, if I kept the rpms to 1200, it would stay cool, at 1500 rpms, it would start to heat up again. 
I took the alternator to the Blue Circle guy I got it from and he bench tested it for 45 minutes with no ill effects, told me the belt was either too tight, or one of the new batteries was bad, old Harvey from blue circle said a alternator should never get hot if set up right.
Anybody got any ideas why, with new batteries, and a new alternator it should get so hot it seized?  Thank you  Bob

[Stu Jackson]

It sounds like a wiring issue.

1.  The C post of your 1-2-B is NOT the B position.  Please re-read my earlier link which clearly said, IN RED, to not confuse the two because i made a mistake when I drew those sketches.  B is a position C is a post where wires are connected.

2.  #6 wire for AO from the alternator to your house bank is very close to being too small.  50A alternator could put out maybe 30 A, #6 wire is good for 30A for 35 feet at 3% voltage drop.  I used a #2 wire.   Much larger.  How are your ground wires arranged?

3.  You have two equal banks with (2) 6V batteries in each bank.  Which did you choose as your "house" bank, i.e., where does your alternator output (AO) go?  How do you charge the second one?  With 4 T105s, 2 on each side of the switch, where does your AO go?  Based on Dave's sketch in Reply #12 in that link, his "start" bank is simply 2 of your 4 6V banks, and the "house" is the other.

Harvey from blue circle said a alternator should never get hot if set up right.

He's right.  Please sketch up a wiring diagram of what you did, like we suggested earlier, 'cuz from previous discussions it appears that perhaps some wiring issues may be in play.  

[SeaFever]

Maine Sail,

I would think that if someone has their nyloc lock-nut melt on an alternator or near the engine somewhere, they have some other issues to contend with. If things are getting hot enough for the nyloc to melt, we have bigger issues... Wouldn't you agree? Having said that, I too use lock washers on most everything around the engine, but then, I guess I am old fashioned and conservative.

Guys : On a related item for the alternator, you should consider using a self locking nut on the output stud rather than a nut and lock washer.  A thought

Ron,

I love nylocs but ever since having melted the "loc" part of one, and subsequently had the nut get loose, I stopped using them on items that can get hot. I still use lock washers on alt outputs and have never had one come loose. I doubt an alt post would get that hot but just a thought...