Alternator Temp; what is normal range?

[Cdn]

Originally Posted by bradfordharley

Sure. I’ll snap a couple while on the boat tomorrow. I have a 4jh80, and there is a kit from yanmar that contains the bits to relocate the fuel filter and the bracket, belt, alternator and pullies to mount on the right side of the motor.
I considered Balmer, but liked the yanmar one better. I like the actual balmer alternators better, but they are 2-3 times the price. I have 2*125 Amp alternators. Yanmar currently uses the valeo ones. If I replace them at any time, I may go balmer....

How much was the kit? Serpentine belt?

Cheers

Nick

[bradfordharley]

Originally Posted by Cdn

How much was the kit? Serpentine belt?

Cheers

Nick

If memory serves, about 1100 for everything. You can get a price from any yanmar dealer. I don’t know if the same applies for the older motors. Mine is the new common rail one.

[Wotname]

For the OP...

Originally Posted by Wotname

AFAIK the stock alternator has an inbuilt temperature control which cuts back the regulated voltage if it gets too hot.

However I don't know the numbers and can't vouch for the veracity of this claim.

Further to this, the manual gives the following information:

Alternator output - 14.5 ± 0.3V (at 20°C, voltage gradient, -0.01V/°C)

which suggests that it is temperature compensated.

[Cheechako]

All I know is the alternator was definitely too hot to touch even momentarily at high output/charging .... even with minimal load.

[tanglewood]

Contrary to common belief, it's the stator that gets the hottest in an alternator, not the diodes. I have seen a stator temp over 300F while the diodes were well below 200F. Neither was a problem, but you wouldn't want to touch it.


The important point is that WHERE you measure temp makes a big difference. The temp sensor that controls a Balmar regulator attaches to the power post, and is designed to control diode temp.


The real issue is that most alternators are designed to recharge a start battery and carry operational power loads. As such, their output "rating" is NOT a continuous duty rating. They assume recharge of a start battery that may accept high current for a while, but not for very long before it tapers down. So they are designed to never run at full output for more than tens of minutes before they will start to over heat.


Now connect that alternator to a big house bank that could be deeply discharged, and you will now be running that alternator at full load an hour or more. It will overhead, and this is why regulators like Balmar monitor temp and back off if it gets too high.


Now add in a really big house bank, or LFP where the current demand never backs off, and you have further exposed the lame, intermittent duty alternator on your engine.


So one way or another you need to de-rate the alternator to whatever it can handle on a continuous basis. I don't think any of the manufacturers will be helpful telling you what that number is, so you will have to figure it out experimentally. I haven't even been very successful in getting manufacturers to say whether the ratings are continuous or intermittent, and if intermittent, what's the duty cycle looks like. Nor have I been able to get solid info on what the allowable stator temps are. It's actually quite frustrating.



When it comes to de-rating, there are basically two ways to do it.


1) Always limit the output current to the continuous duty level.


2) Monitor temp, and use a feedback loop to reduce output when temps get too high. For an alternator that is really worked hard, I'm not convinced that the Balmar approach of only measuring diode temp is sufficient. I'd feel better if stator temp were factored in too because stator temp will vary with the square of the output current, where diode temp will vary linearly. But maybe stator temp follows diode temp closely enough to work well enough.


Or of course you could switch to a continuous duty alternator, but they are generally much larger and I gather won't fit an smaller engines. My own experience is with larger engines, and this is the route I have gone.

[Frankly]

Per #2 above.

I have an older Balmar small case 100 amp controlled with a 612 regulator. The 612 is set up so if you short the alt temp sensor terminals the output is reduced to half. I have a panel mounted switch to put it in this mode (Balmar calls this small engine mode). I run it in this mode almost always because it reduces the strain on all the components (belt, alternator, engine).

Few years back bought one of these cheap temp controllers off ebay. Connected the temp sensor to the alternative case and the output in parallel with the small engine switch. Now if I put the switch in full output the controller takes over. Have the temp set at 190 drgrees F. Works quite well. With a seriously discharged bank (600 AH GC2) the temp will get to 190 in less than 20 minutes. Open the motor box and that temp drops like a rock with some cooler air to circulate. Still thinking about best way to bring some cooler air to the alternator before I get out the hole saw.


Frankly

[Disailor]

Info on this subject at www.marinehowto.com

[careka]

did a test today, i have a LiPo4 bank of 800 amps, and Yanmar 3YM30 motors. with smal case Hitaci 60 amp altenators. i took the bank way down during the nigth, and started the motors, to check the temp on altenators, while motor was only doing 1000rpm, i got 47 amps. from altenator, revving up to 2000rpm. it gave 60 amp. and slowing down to 55.. i was in and out of motor room to check temp, after motor was good and hot, temp on altenator, (shot with infraread). around 78`C. when idel revs, and went down to 71`C. at 200rpm. i belive these altenators. dont have temp control and i am not sure how high they will go on Volts. ? but so fare it looks good.

[model 10]

Measuring the temp anywhere on the back of the case is very misleading. We lost our fancy regulator this year and I went to a simple fixed 13.9 spare. The case temp was pretty hard to control. The temp would climb to 225 quickly but the power term and the diode area would stay at pretty much engine temp. I installed a switch for the field and turned it off at about 230 deg and then the case would cool down to engine temp in maybe 15min. After all the batts were charged the rear of the case would drop to about 140deg from the front mounted fans help.

[Sternwake]

Originally Posted by tanglewood

Contrary to common belief, it's the stator that gets the hottest in an alternator, not the diodes. I have seen a stator temp over 300F while the diodes were well below 200F. Neither was a problem, but you wouldn't want to touch it.

....snip

Was this stator temp taken on the exterior of the alternator casing itself?

Does it make any sense to pepper the exterior casing of alternators with finned heatsinks if there is sufficient room to add them?. I've got lots of salvaged finned heatsinks laying around I could bend to the casing's radius.



I have used some arctic silver thermal epoxy to attach a K type thermocouple to my alternator casing, but had always thought the diodes would be much hotter, and was considering adding a K type thermocouple to the rectifier plate, to see the difference, but never got around to it.

[a64pilot]

The Stator May in fact be the hottest, I don’t know, but I feel pretty sure it would be difficult to measure its temp, so us mere mortals measure the case temp, and the side of the alternators case that the diodes are located will run hotter.
Any form of cooling, heat sinks etc will help, how much would depend on how well they dissipate heat.
I set mine up IAW Maine Sail’s instructions except I turned the allowable alternator temp down to 90c and it’s gets there pretty quick. I used belt manager 4 on my Balmar 614 regulator.
The most I will see from my 165 amp alternator at cruise RPM is about 90 amps.
However I’m fine with that, after I learned on this site that for my particular Yanmar the max allowable torque that can be pulled off of the crank is 4 HP at my cruise RPM of 1800 and that is about 100 Amps, if I pull more than that I’m exceeding the engines limit, and will probably shorten its life.

[wsmurdoch]

Mike Bradfield has a paper here https://www.electronics-cooling.com/...r-electronics/ that you can view on line for free.

There is also a SAE paper https://saemobilus.sae.org/content/960272/ that has both measured and calculated data. But, the copy that is for sale is black and white making it impossible to recover much of the data. You might be able to get a color copy on an inter-library loan, but I have not tried. If you want a B&W copy, drop me a PM. The alternator looks like a CS-130D.

The major results are in this table. "Case A is the baseline design (alternator rotation speed at 1900 rpm, including rear and front fan) with radiator cooling fans rotating counter-clockwise (viewed from passenger compartment) at 1900 rpm. Case B is the baseline design alternator with radiator cooling fans rotating clockwise. Case C is the design without rear fan and radiator cooling fans rotating counter-clockwise. Case D adds additional shielding..."

Bill

[GordMay]

Originally Posted by a64pilot

... Any form of cooling, heat sinks etc will help, how much would depend on how well they absorb [“thermal uptake”] and dissipate heat ...

Edit.