Alternator overheating

[roetter]

I have a Volvo D2-40 with Mitsubishi 115A alternator.
The engine room has pretty good sound and heat insulation and is quite small, so it heats up well. The only air circulation is the air the engine draws in through an opening.

With the batteries fairly low the following happens:
- Alternator starts charging at about 80A (+15-20A for instruments, fridge etc). So it is close to the max rating.
- It quickly regulates down to 40-50A (+15-20A), total time 30 minutes
- Then it stops charging completely for about 5 minutes


The next cycle it charges for about 20 minutes then shuts down for 5 minutes, next cycle is less than 20 minutes. When I open a panel to the engine room it tays on a little longer.

It works, but I would like to get more charge power into the batteries.

I plan to replace my broken IR thermometer to take some temperature readings.

Options:
- add a fan that blows fresh air near the alternator, connected to ignition so it only runs when engine is running
- change to a hot-rated alternator
- add a second alternator
- open this alternator and see if anything is wrong

- other options?

[hellosailor]

"I plan to replace my broken IR thermometer to take some temperature readings."
Before there were such things, there were "mechanics crayons" made of waxes that melted at different temperatures. Really. I have no idea if they are still made today.

Is your engine/alternator installation custom, or standard on that boat? Any similar owner complaints or factory advisories, if it is standard?

I would think that the only way to "bench" test the alternator would be to use a conventional window fan to blow cold air into the engine bay, ensuring there's an airflow, and then waiting patiently to see if the alternator still overheats.

But there are also sometimes fan kits, or options, to put dual fans (front and rear) on alternators, that would be option#1 to cool it. Assuming the alternator is new not a rebuilt, because some rebuilders throw an extra coat of shiny paint over everything and that's also enough to cause overheating.

If rigging an exhaust blower to blow fresh cooler air over the alternator is enough to make it happy, that may be the simplest solution. But measuring the ambient temp in the engine bay will give you one piece of the puzzle, the other is simply whether that alternator is being overworked for that job. It might be belted up with the wrong size pulley, running too fast (= hot) or simply putting out more power for longer than it is designed for, in which case a larger alternator might be the answer.

You've got some exploring to do.

[Cheechako]

A half hour (max) at high output is about all you are going to get out of an alternator with a good regulator. The shutting off completely is wierd though.... maybe it's doing so due to overheat? (seems like my Next Step regulator only pushed my alt's to max for 20 mins or so...before stepping down.... even with the batt's quite low?)A hard driven alternator gets very hot (too hot to touch) I thoguht about making a copper tube water cooling coil to put around mine as an experiment once, never did though.... seems like the other limitation is the batteries ability to take it that fast for too long....

[Maine Sail]

#1 Remove alt and have it wired for external regulation by bypassing the internal regulator and tapping into the field/brush assembly. Your alt seems to be temp compensating and shutting itself down on safety.

#2 Buy a Balmar MC-614 regulator & alt temp sensor

#3 Program the regulator in "belt manager" for level #3. This limits the field output and essentially limits the alt output or derates the alternator. It will essentially set a current limit below the alts max output.

#4 Run the alternator loaded to see if the alt goes into temp liming or exceeds 215F - 225F. A good trick to "load the alt", if the batteries are not deeply discharged, is to run an inverter using a ceramic disc heater, hair dryer or heat gun as the load. This will send the alt into bulk mode and it will stay there until you turn off the inverter. It will give you plenty of time to heat up the alt and adjust the regulator settings to find your max safe output. This is the best way to set up an alt as you don't need to have a discharged bank to do so..

If the alt temp limits at belt manager level #3 then go back into belt manager and move it to level #4. Derate the alternator in belt manager until you find the max continuous output the alt can run at and remain below 225F.... Contrary to popular misconception this is not robbing you of alt output it is actually maximizing the maximum safe limit the alt can physically run at continuously in YOUR engine room.. Derating the alt will give you an alternator that can run at the new output all day long and not cook itself. You NEVER get full output from an alt anyway but pushing them hard, as you are doing, will only lead to an eventual failure... Even high dollar, high output alts benefit from purposely over-sizing them then derating them in belt manager..

As an example the 160A high output alt in our boat is set to a max of 110A-115A. This is simply the most it can run at, in our engine compartment, without exceeding 225F, and I have cooling ducts to help the engine bay stay cooler........

[roetter]

I have taken the alternator home and blew out the dust from it, specifically from the cooling fins of the regulator. I put it back in and did some teasing. It appears to be better now. However, the weather was a little bit cooler. Here are the results.



Overall, it appears no to be overheating anymore and completely shutting down. Still, it would be great to get more out of it for a faster recharge.

[colemj]

Originally Posted by Maine Sail

#1 Remove alt and have it wired for external regulation

Doing that is a problem with the Volvo D2-40's engine management system. It causes alarms to go off with no easy way to make them stop. Also a problem when putting aftermarket alternators on these engines.

There is a thread here about that, and someone finally seemed to solve the issue, but I don't remember.

Mark

[FlyingCloud1937]

It's actually quiet easy and only requires one relay. But you must bring out the field wires from the alternator.

Lloyd

Originally Posted by colemj

Doing that is a problem with the Volvo D2-40's engine management system. It causes alarms to go off with no easy way to make them stop. Also a problem when putting aftermarket alternators on these engines.

There is a thread here about that, and someone finally seemed to solve the issue, but I don't remember.

Mark

[deckofficer]

Originally Posted by Maine Sail

#1 Remove alt and have it wired for external regulation by bypassing the internal regulator and tapping into the field/brush assembly. Your alt seems to be temp compensating and shutting itself down on safety.

#2 Buy a Balmar MC-614 regulator & alt temp sensor

#3 Program the regulator in "belt manager" for level #3. This limits the field output and essentially limits the alt output or derates the alternator. It will essentially set a current limit below the alts max output.

#4 Run the alternator loaded to see if the alt goes into temp liming or exceeds 215F - 225F. A good trick to "load the alt", if the batteries are not deeply discharged, is to run an inverter using a ceramic disc heater, hair dryer or heat gun as the load. This will send the alt into bulk mode and it will stay there until you turn off the inverter. It will give you plenty of time to heat up the alt and adjust the regulator settings to find your max safe output. This is the best way to set up an alt as you don't need to have a discharged bank to do so..

If the alt temp limits at belt manager level #3 then go back into belt manager and move it to level #4. Derate the alternator in belt manager until you find the max continuous output the alt can run at and remain below 225F.... Contrary to popular misconception this is not robbing you of alt output it is actually maximizing the maximum safe limit the alt can physically run at continuously in YOUR engine room.. Derating the alt will give you an alternator that can run at the new output all day long and not cook itself. You NEVER get full output from an alt anyway but pushing them hard, as you are doing, will only lead to an eventual failure... Even high dollar, high output alts benefit from purposely over-sizing them then derating them in belt manager..

As an example the 160A high output alt in our boat is set to a max of 110A-115A. This is simply the most it can run at, in our engine compartment, without exceeding 225F, and I have cooling ducts to help the engine bay stay cooler........

I'm always learning from your posts. The OEM calls it "Belt Manager" I assume for matching max load to acceptable belt life?

[Stu Jackson]

Originally Posted by deckofficer

I'm always learning from your posts. The OEM calls it "Belt Manager" I assume for matching max load to acceptable belt life?

Yes, Bob. Welcome to Balmar You can download the manuals and read more.

Maine Sail is a proponent, with good reason as he's explained, of belt manager.

I use Small Engine Mode. It's a manual way of initiating the temperature 50% cutback feature. Also in the manuals.

MC-614 (we have an older MC-612).

Small Engine Mode - discussion with link to the picture of the toggle switch: http://c34.org/bbs/index.php/topic,4....html#msg27149

Maine Sail recommends BOTH alternator and battery temperature sensors, I have neither.

[deckofficer]

Originally Posted by Stu Jackson

Yes, Bob. Welcome to Balmar You can download the manuals and read more.

Maine Sail is a proponent, with good reason as he's explained, of belt manager.

I use Small Engine Mode. It's a manual way of initiating the temperature 50% cutback feature. Also in the manuals.

MC-614 (we have an older MC-612).

Small Engine Mode - discussion with link to the picture of the toggle switch: Alternator heat, Regulator Controls, Small Engine Mode

Maine Sail recommends BOTH alternator and battery temperature sensors, I have neither.

Thanks Stu, I'll read up on it but you guys are making it easy. I would prefer to run 20 minutes at max charge to put in on a low solar day what I used, than 40 minutes with the max output de-rated. If the belt is up to it, I want the diesel loaded a bit more for its run time. If I ran the battery bank low on a regular basis (and I wouldn't do that to LiFePO4 cells), then using the "Belt Manger" at a setting that would allow the most output per longer time frame without the larger roll back of the temp sensor circuit would be the way to go.

Thanks guys.

[Stu Jackson]

I agree, Bob. It's a resources management issue.

Your boat, your choice.

[roetter]

I just found that the Hitachi alternator regulator specifications are for an alternator temperature of 20C with a gradient of -0.01V/C. That means if the alternator is set for 14.2V at 20C, at 60C it will regulate down by -0.4V to 13.8V.

My Mitsubishi alternator was running at about 60C at measured at the regulator fins. If it has the same gradient it would regulate also down by 0.4V.

Does anybody know the voltage/temperature gradient values for the Mitsubishi alternators?

I guess I could repeat my test and put a Junsi CellLog at the alternator sense location and record the voltage with temperature measured at the regulator fins.