Alternator overheat solution

[wmcunninghamii]

I have been experiencing alternator overheats since installing new AGM batteries which replaced 13 year old lifelines. The weather out here in Norcal has been pretty hot recently so that is not helping.

I have a Freedom 30 with a very tight engine space. I do not have a ton of options re vent hoses, fans, etc.

One possibility I have been pondering is drilling some ventilation holes in the side of the companionway steps box which covers the engine space. The steps are removable to get at the engine and doing the drilling would be fairly straightforward. It is easy to do measurements such that the drilled holes with line up with the location of the alternator. The holes would be about three inches from the alternator case.

My thinking is that the Yan 2GM20F probably pulls several hundred cubic feet of air per minute when it is operating at 2500 RPM. The engine air intake is like a super vacuum cleaner when powering at this speed. So, if I created an air intake vent in the companionway steps box right adjacent to the alternator it seems like the net effect will be a nice stream of outside air over the alternator on its way to engine air intake. Currently air gets in there through various crevasses in the surrounding wood structure front and back of the engine. There is no dedicated ventilation port so I assume there is always some negative pressure inside the engine space. The proposed vent holes ought to provide pretty good air flow over the alternator going on the assumption air will flow to low pressure via the path of least resistance.

I could also be crazy. I would appreciate comments on this approach to cooling the alternator.

I do realize that the vent will likely allow some engine noise to escape the box but in cooler/cold weather I would plan to place a cover over the vent if the additional noise was significant.

I guess I should also mention I have a Balmar ARS5 regulator and have installed a "small engine" switch which reduces field current by 50% when it is active. I can run all day in this mode but the charging capacity of the alternator is very significantly reduced and low current provided to the AGMs when they should be bulk charging is not ideal.

[tkeithlu]

You've covered the basics that I immediately thought of - maintaining negative pressure, directed cool air, amperage, and noise. But, why is it overheating? The usual answer is running too small an alternator, such that you are going to burn it up, but you've got a sophisticated current regulating system in place. Have you considered an additional fan on the alternator? Take a look at this:

https://www.summitracing.com/parts/s...hoCL4IQAvD_BwE

My only other thought is whether some baffling might help with the possible noise problem. You might try a sliding door for the holes, as well, and find out how much you need to keep it cool.

I just re-read your original post, and I'm still a little suspicious that you might have too small an alternator.

[Sternwake]

Seems like a good idea. ... If the engine intake is really that restricted and it is not easily pulling in all the air it needs from elsewhere.

Where you drill the holes, perhaps a hood lined with damping material on the interior to lessen noise radiating outwards.

Perhaps drill one small hole, tape a streamer above the hole, and set your smartphone video camera on it with assistive light activated, close it up and start the engine and rev it to cruising rpms. See how much streamer movement there is. If there is not very much then more larger holes and the whole effort might be wasted unless you installed a powerful intake fan there instead.

I'm a bit of a ventilation lunatic and I find that one single powerful fan pushing, or pulling, is not nearly as effective as two less powerful fans doing both together. Of course two powerful fans doing both is even better, especially when both are on speed controllers and dialed up only as much as needed or to a tolerable noise and flow level.

If you go for an interior mounted pusher fan....

The Delta FFB1212EHE is my favorite 120mm/4.75 inch x 38mm thick fan.
The hub's support/steering vanes concentrate the accelerated air flow into a dense column, easily aimed/ directed. It responds nicely to voltage as a speed controller. Such fans are not marine Ized. I remove the impeller by lifting the sticker and removing the C clip on the hub. I use clear nail polish to cover all circuit board traces and component legs in a layer or 3, then once dry I use Amazing goop to close off where the power wires enter the hub and the one other gap on hub perimeter. This fan has no issues with battery charging voltages either. Draws less than 2 amps @12v, the 3 amps listed on sticker is the start up surge and I rarely run them at 11+ volts as they are so powerful.

The flow from this 120mm delta fan dwarfs the radial flow of my alternator's external fan when it is spinning at high rpm.

Delta has other high rpm fan models with the flow channeling steering vanes ahead of impeller. 92mm and 80mm and 140mm. I dont have all their part numbers handy at the moment. There is one 120mm fan with a 252 cfm rating which does NOT respond well to voltage or PWM modulation as a speed control, and is still rather insanely loud for most tasks when run at its minimum speed. when controlled by either PWM on inputs or voltage.

Anyway consider the hole size when cutting, in case you decide to later install fans here, and the engine itself is pulling in air from other locations easily.

A k type thermocouple on the alternator itself, with display easily viewed while underway, should allow you to dial up the field current for more bulk amperage into depleted AGMS, which seem to behave so much better when fed high amperage from well depleted states. in my experience/close observations.

Also consider a radiant heat shield between alternator and manifold, if possible. No sense fighting both convective and radiant heat when one of them can be blocked.

[Stu Jackson]

Originally Posted by wmcunninghamii

1. I have been experiencing alternator overheats since installing new AGM batteries which replaced 13 year old lifelines. >>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>


2. I guess I should also mention I have a Balmar ARS5 regulator and have installed a "small engine" switch which reduces field current by 50% when it is active. I can run all day in this mode but the charging capacity of the alternator is very significantly reduced and low current provided to the AGMs when they should be bulk charging is not ideal.

1. Why were you surprised? AGMs have far more acceptance than FLAs.


2. Good idea. But you may have failed to recognize the beauty of SEM as you have it installed. Once your charging amps start dropping off to what your alternator can safely produce, then switch SEM OFF again.


Your issue is that you may have too small an alternator for the AGMs - see #1.


I would seriously reconsider your idea about ventilation. It's not a good idea, and you may not need it.


And with your Yanmar engine, you could most likely have a Hitachi alternator. In which case, you should have seen this, which Maine Sail wrote I keep reposting.



Your problem is your alternator, not ventilation. Good luck.


*************************************************
Hitachi/Yanmar Alternators: (by Maine Sail)

Some alternators though, such as those made by Hitachi and found on Yanmar diesels, are dumber than a pound of beetle poop. Actually, to the alternator, they are pretty smart but to your batteries and the speed of charging they are flat out stupid. Why?

Hitachi alts with dumb regulators, and some others, limit voltage but also reduce voltage based on alternator temperature. This is a self protective feature installed in the internal dumb regulator to prevent the alternator from cooking itself. Remember voltage is the pressure that allows more current to flow. So, if we reduce the absorption voltage, then we also reduce the current the alternator is supplying.. Any battery at any state of charge simply will not accept the same current at 13.4V that it did at 14.4V and as a result the alternator will run cooler. What do you suppose this does to your batteries over time.......?

The problem is that when cold you will get 14.3V to 14.4V out of the Hitachi but as the alternator heats up the dumb regulator begins to reduce the CV/voltage limit based on the alternators internal temperature. It is not uncommon to find a Hitachi alternator at 13.4V when hot. This is REALLY, REALLY DUMB....

If you have a dumb regulator, and notice the voltage dropping, it is likely a temp compensated dumb regulator. Get rid of it or plan to buy new batteries more often.

If you have a temp compensated alternator or a Hitachi alternator on a Yanmar you really are in dire need of external regulation if deep cycling a larger battery bank.

This is from:

http://forums.sbo.sailboatowners.com...d.php?t=125392

and these, too:

http://www.cruisersforum.com/forums/...on-125843.html


http://www.cruisersforum.com/forums/...or-142083.html

[a64pilot]

Good luck, the problem is you and many others are trying to use a boy to do a mans job, and the boy just isn’t up to it.
However you should be able to get 90 amps or so out of a small frame alt, I can anyway.
Much over 90 amps just isn’t in my opinion possible or advisable, but running one very hot, your shortening it’s life.
I limit mine to 95C which is conservative, but I think it will last years longer that way

Using electric fans of course pull power, so if a fan pulls 10 amps and you get 10 more amps out, what has been accomplished?

Before I cut holes etc into the boat, I’d try a bilge blower that pulls cool air from the bottom of the bilge and blows onto the back of the alternator, the back side has the diodes and therefore is the hot end.
Most alts have two fans and actually suck air in from the front and back and blow it out of the middle.
They don’t move much air though.

A big problem with small frame alternators and heat is we are seriously under speeding them. They are meant to be turned much higher RPM which means they generate less heat and the fans remove the heat better.
Off the top of my head I believe they should be spun about 10,000 RPM to get high power and good cooling and we usually spin them about half that. Max RPM is about 18,000. That’s just a generic number of course, some will be lower and a few may be higher.
Often the crank to alternator pulley ratio is about 3 to 1.

[wmcunninghamii]

Originally Posted by tkeithlu

You've covered the basics that I immediately thought of - maintaining negative pressure, directed cool air, amperage, and noise. But, why is it overheating? The usual answer is running too small an alternator, such that you are going to burn it up, but you've got a sophisticated current regulating system in place. Have you considered an additional fan on the alternator? Take a look at this:

https://www.summitracing.com/parts/s...hoCL4IQAvD_BwE

My only other thought is whether some baffling might help with the possible noise problem. You might try a sliding door for the holes, as well, and find out how much you need to keep it cool.

I just re-read your original post, and I'm still a little suspicious that you might have too small an alternator.

I have a 70 Amp Balmar alternator and a 2 battery house bank of 115AH AGMs for a total house of 230 AH. The start batt is identical to house (115 AH AGM) is isolated and charging via Xantrex echo charger from the house bank. The house bank size is well within Balmar's recommendations re alternator sizing.

What leads me to believe lack of cooling is a problem is when I look at my alternator output during overheat episodes it rarely exceeds 12 amps this does not seem to be an excessive load on the alt.

I will check out the additional fan idea, thank you.

[wmcunninghamii]

Originally Posted by Stu Jackson

1. Why were you surprised? AGMs have far more acceptance than FLAs.


2. Good idea. But you may have failed to recognize the beauty of SEM as you have it installed. Once your charging amps start dropping off to what your alternator can safely produce, then switch SEM OFF again.


Your issue is that you may have too small an alternator for the AGMs - see #1.


I would seriously reconsider your idea about ventilation. It's not a good idea, and you may not need it.


And with your Yanmar engine, you could most likely have a Hitachi alternator. In which case, you should have seen this, which Maine Sail wrote I keep reposting.



Your problem is your alternator, not ventilation. Good luck.


*************************************************
Hitachi/Yanmar Alternators: (by Maine Sail)

Some alternators though, such as those made by Hitachi and found on Yanmar diesels, are dumber than a pound of beetle poop. Actually, to the alternator, they are pretty smart but to your batteries and the speed of charging they are flat out stupid. Why?

Hitachi alts with dumb regulators, and some others, limit voltage but also reduce voltage based on alternator temperature. This is a self protective feature installed in the internal dumb regulator to prevent the alternator from cooking itself. Remember voltage is the pressure that allows more current to flow. So, if we reduce the absorption voltage, then we also reduce the current the alternator is supplying.. Any battery at any state of charge simply will not accept the same current at 13.4V that it did at 14.4V and as a result the alternator will run cooler. What do you suppose this does to your batteries over time.......?

The problem is that when cold you will get 14.3V to 14.4V out of the Hitachi but as the alternator heats up the dumb regulator begins to reduce the CV/voltage limit based on the alternators internal temperature. It is not uncommon to find a Hitachi alternator at 13.4V when hot. This is REALLY, REALLY DUMB....

If you have a dumb regulator, and notice the voltage dropping, it is likely a temp compensated dumb regulator. Get rid of it or plan to buy new batteries more often.

If you have a temp compensated alternator or a Hitachi alternator on a Yanmar you really are in dire need of external regulation if deep cycling a larger battery bank.

This is from:

http://forums.sbo.sailboatowners.com...d.php?t=125392

and these, too:

https://www.cruisersforum.com/forums...on-125843.html


https://www.cruisersforum.com/forums...or-142083.html

Apologies, I was not very clear.

The 13 year old Lifelines which I replaced were AGM's and the Balmar 70 amp alternator I currently have was installed when I originally installed the Lifeline AGMs specifically because the stock Hitachi alternator was not up to the task of charging them. So Hitachi, at least, is not one of my problems.

I am externally regulated with a Balmar ARS5 with small engine mode switching capability installed by me. The regulator is temp compensated to both the alternator and the batteries. I have the belt load manager on the regulator set to B-3 which is a 15% reduction in field potential. I also have a serpentine pulley/belt upgrade kit installed to eliminate belt dusting and any slippage.

Now that I am writing this, perhaps I should take another look at my belt load manager settings? I did not change this when I replaced the AGMs. Maybe I need to consider taking BLM down another 5 or 10% and see if that helps with heating.

[wmcunninghamii]

Originally Posted by a64pilot

Good luck, the problem is you and many others are trying to use a boy to do a mans job, and the boy just isn’t up to it.
However you should be able to get 90 amps or so out of a small frame alt, I can anyway.
Much over 90 amps just isn’t in my opinion possible or advisable, but running one very hot, your shortening it’s life.
I limit mine to 95C which is conservative, but I think it will last years longer that way

Using electric fans of course pull power, so if a fan pulls 10 amps and you get 10 more amps out, what has been accomplished?

Before I cut holes etc into the boat, I’d try a bilge blower that pulls cool air from the bottom of the bilge and blows onto the back of the alternator, the back side has the diodes and therefore is the hot end.
Most alts have two fans and actually suck air in from the front and back and blow it out of the middle.
They don’t move much air though.

A big problem with small frame alternators and heat is we are seriously under speeding them. They are meant to be turned much higher RPM which means they generate less heat and the fans remove the heat better.
Off the top of my head I believe they should be spun about 10,000 RPM to get high power and good cooling and we usually spin them about half that. Max RPM is about 18,000. That’s just a generic number of course, some will be lower and a few may be higher.
Often the crank to alternator pulley ratio is about 3 to 1.

I wish I could get some of that cool air out of the bilge but I just do not have the room in my installation to run any significant ducting into the engine room. I need to figure out a way to provide some cooling without ducting if at all possible. I might be able to fit a muffin fan although I was hoping the vacuum created by the engine intake would suffice to provide good airflow through any ventilation holes I create in the vicinity of the alternator.

I hear you re cutting holes in the boat!!That is one of the reasons I am looking to the community for alternative ideas.

[wmcunninghamii]

OK, I just looked at one of the threads Stu Jackson recommended in his post. One person proposed something very similar to what I had in mind. But they suggested using the negative pressure caused by the engine intake to bring cool air from the bilge into the alternator via a duct. I can't fit a duct but the poster also mentioned the location of the engine air intake and that made me think about my situation. The mouth if the air intake on my Yanmar is about six to ten inches from the alternator case. What if I were to use a generous size duct from the engine intake to the back end of the alternator? I would not want to obstruct the air intake whatsoever but if I could pull a lot of air from the vicinity of the alternator this might set up some good airflow which I do not have now.

It would also eliminate the need to drill anything if successful.

And, BTW, thank you all for sharing your thoughts. It really got me thinking about some alternatives I had not considered.

[a64pilot]

Originally Posted by wmcunninghamii

I have a 70 Amp Balmar alternator and a 2 battery house bank of 115AH AGMs for a total house of 230 AH. The start batt is identical to house (115 AH AGM) is isolated and charging via Xantrex echo charger from the house bank. The house bank size is well within Balmar's recommendations re alternator sizing.

What leads me to believe lack of cooling is a problem is when I look at my alternator output during overheat episodes it rarely exceeds 12 amps this does not seem to be an excessive load on the alt.

I will check out the additional fan idea, thank you.

You have something going on if you can’t pull more amps than that.
What makes you say it’s overheating, do you have a temp sensor on it?

[smac999]

if your alt is overheating charging 12a to a tiny 100ah battery something else is wrong.

maybe the bearings are bad or something.

[wmcunninghamii]

Originally Posted by smac999

if your alt is overheating charging 12a to a tiny 100ah battery something else is wrong.

maybe the bearings are bad or something.

Yea, I am a little concerned about that too. I had the alternator out of the boat about a week ago to install the serpentine pulley. I did spin the alternator to see if I could detect any type of roughness, looseness or noise but seemed pretty smooth, solid and quiet, I couldn't detect any side to side or backward forward shaft movement.

I do have belt manager limiting field potential to 85% of max.

I definitely detect the alternator kicking in when the engine is at idle, I can actually hear the engine loading up. So the alt is doing some non trivial work. I need to reverify the current output though. I may have misread the monitor.

BTW, The heating issue preceded the serpentine belt install.

One issue I have with testing is I rarely run my batteries down below about 85%. I sized the system for some long distance ocean racing I was doing so I have a considerably larger bank (and weight) than I need for casual cruising. At anchor I have an SA which keeps the Batts pretty well topped up during the day. My baseline hourly power consumption is between 24 and 36 watts. On a 230AH house bank that would be about 35 AH down if I head out in the morning before the SA kicks in. Would an AGM at that SOC demand a ton of alternator amps during charging?

[wmcunninghamii]

Originally Posted by a64pilot

You have something going on if you can’t pull more amps than that.
What makes you say it’s overheating, do you have a temp sensor on it?

Yes, I have a temp sensor on the alt, the Balmar alarm log is displaying an overtemp event and my panel lamp lights up (as it should). When I switch to small engine mode the panel lamp will go off after a few minutes which indicates to me that the alt has cooled down a bit. When I use my IR gun to check the alt right after an alarm, it is HOT! around 240F (115C).

As I mentioned in another post, I am going to recheck my work on the amp output of the alt when it gets hot. I may have misinterpreted my monitor.

[14p]

I read they get REAL hot and its normal. My Delco 1960s 10DN 50 amp get too hot to keep your hand on more than 1 second, thats even just starting and idling a few minutes, AGM Harley batteries, ETX30L 12 volts in series

I was wondering if drilling holes in the case and making it like the mini Denso alternators with lots of open grooves for cooling might cool it down? Than again maybe its happy hot?

I found quote below on web, says 200f is ok, now to put a thermometer inside while running somehow to tell how hot it is getting.

"When they are putting out higher amps, they will get hot enough to burn you, up to 200F or so. The closer you are to the rating of the alternator, the hotter they get. The cheap alternator get hotter IME- they are generally pushing the compon ents to the edge.

As pointed out above, any loose or weak components strain the alt and make it heat more."

[wsmurdoch]

Originally Posted by 14p

I was wondering if drilling holes in the case and making it like the mini Denso alternators with lots of open grooves for cooling might cool it down? Than again maybe its happy hot?

GM used the 10DN alternator from 1963 to 1972. That was a long time ago, and they have made progress since. https://alternatorparts.com/how-to-i...lternator.html For some idea of the improvements that have resulted in the open frame alternator designs look at https://www.electronics-cooling.com/...%20electronics. It is more than a few holes.

Bill