Vetus Alternator optimization

[txg]

Our 2015 Vetus M4.35 has the stock 110A Alternator without external sense or external controller. I have no idea who built the alternator and there's no identification sticker on it.

It's connected to the 220Ah AGM house bank with 2/0 cabling.

When i start the engine and rev up a little bit, charge current with batteries at about 50% goes up to about 80A. While that's good at first, current directly starts to go down within few minutes, without the battery bank hitting absorption voltage (14,1V with my alternator, which is quite low but that's probably not the problem here). About an hour of running, current has gone down to less than 30A, even if the battery is still only hitting 13,5V. I've measured the voltage directly at the alt and got 13,65V.

I've read the article of maine sail about alternators with internal temperature compensation before and so i measured the alternator temperature. It was at 107°C or 225F. Looks like the alternator cuts down charge current to protect itself.

While this is probably a good feature it also means that using an external charge controller won't help anything as the temperature is the problem and not the regulator.

Does anyone have similar experiences? I know there is an older thread about alternator cooling, but i'm hesitant to cut a hole in the engine room and install a fan due to noise. Our main energy source will be our solar system so hopefully we won't need to use the alternator very often simply for charging, but if we have to, i would like to have better performance than now.

[smac999]

a 220ah bank is tiny for a 110a alt. your alt is totally over kill for that bank. and certainly shouldn't be overheating if it's barely putting out amps.

an external reg might help. pull the alt off and an alt /starter shop can easily mod it for use with ext reg. and buy a ext reg.

get the balmar mc6-12 and run the belt setting around 70%. it'll run cooler and that's all the power you'll likely get into that small bank anyways. and get the alt temp sensor.

[geoffr]

Sounds like it's working fine. You Battery is probably not able to accept more than what you are seeing.

Assuming a 50 dod that's only 110 Ahr to replace which would normally take a couple hrs as the current will tail off as it gets charged.

Sent from my SM-G920W8 using Cruisers Sailing Forum mobile app

[txg]

While i do appreciate your answers, i think they're not actually helping. With the numbers i provided in my post, it's quite clear that it's not our small battery bank that is limiting the current but the alternator, as the battery is not hitting the 14,1V charge voltage point.

So as far as i can guess, the alternator is not working fine, as it should charge at full current until the battery hits its charge voltage and then reduce current to hold the voltage. But what's actually happening is that the alternator reduces charge current sooner, probably due to its high temperature.

[offpist]

Maybe the alternator is sensing the voltage at the alternator, not the battery. Remember there is also voltage drop at the - cable.

[txg]

As i wrote in the start post, the alternator has no external sense and i measured 13,65V directly at the alt after it reduced its output to less than 30A, so voltage drop is not the issure here.

[DeepFrz]

The alternator is running hot at fairly low output. I would suggest you get some cooling air on to it. Its hard to tell for sure from one picture but it looks like the alternator can't breath very well. What is the ambient temp. in the engine room when the alt. hits 107c? If the ambient engine room temp. is high then you need to supply cooling air to the whole system.

[txg]

Engine Room Temperature with the lid closed is 51°C, so it's not extremely low but not too high.

When i try to feel the air that the internal fan of the alt should move, there's barely anything to feel.

[txg]

I've tried again with the engine bay open, but charge current increased just a little bit. The alt still measures about 100°C.

I've searched around the forum and found mainesails conversion to external rectification which seems like an interesting idea. For someone with electrical experience it's an easy and cheap mod to do.

I'm wondering why no one ever tried to add watercooling to the alternator? As most of the heat is generated in the stator with good contact to the casing, this could probably help a lot. My idea would be to use a 3/4 pipe, hammer it flat on the inside, bend it around the alt and glue it on with thickened epoxy. On my engine, it could be connected between impeller and heat exchanger without needing a lot of extra hose. Should take away a lot of the heat from the alt.

[GordMay]

Several manufacturers offer water cooled alternators.
Ie: Mercedes, Audi, BMW and others

[txg]

I know, but i haven't found anyone who installed one like this in a marine environment, and i'm more interested in the conversion of an existing alternator. If it could charge at 80A continuously i would be totally satisfied.

[geoffr]

Before going to the effort to add water cooling you may want to try a test with a can of cold spray ( http://www.mgchemicals.com/products/...-cold-134-403a )

If spraying the alternator while operating doesn't change the output, then the watercooling probably won't help.

[Panacea2183]

Originally Posted by txg

Our 2015 Vetus M4.35 has the stock 110A Alternator without external sense or external controller. I have no idea who built the alternator and there's no identification sticker on it.

It's connected to the 220Ah AGM house bank with 2/0 cabling.

When i start the engine and rev up a little bit, charge current with batteries at about 50% goes up to about 80A. While that's good at first, current directly starts to go down within few minutes, without the battery bank hitting absorption voltage (14,1V with my alternator, which is quite low but that's probably not the problem here). About an hour of running, current has gone down to less than 30A, even if the battery is still only hitting 13,5V. I've measured the voltage directly at the alt and got 13,65V.

I've read the article of maine sail about alternators with internal temperature compensation before and so i measured the alternator temperature. It was at 107°C or 225F. Looks like the alternator cuts down charge current to protect itself.

While this is probably a good feature it also means that using an external charge controller won't help anything as the temperature is the problem and not the regulator.

Does anyone have similar experiences? I know there is an older thread about alternator cooling, but i'm hesitant to cut a hole in the engine room and install a fan due to noise. Our main energy source will be our solar system so hopefully we won't need to use the alternator very often simply for charging, but if we have to, i would like to have better performance than now.

Agreed that temp is way to high not sure why.
As far as voltage is concerned, if the alt does not have a three stage regulator
It's probably operating as designed. Most standard alternators have one voltage setting. Mine is about 13.7 worthless for charging the batt bank. Just keeps it at float to replace current being used by electronics under way.

You can replace the regulator with en external 3 stage one. Take it to a local alternator shop and have it checked t the same time, may have a bad internal connection or dirty heat sink. Should be no need for water cooling on a 100 amp alt. Cars and light duty busses use them all the time w/air cooling. As far as ambient temp is concerned talk a reading under the hood of your car in the summer, you'll find temps much higher than your engine room.

[txg]

I finally found the solution to this problem by taking the alternator out because of wondering what's wrong as i felt like the charging current got even lower over time.

as i said before, i measured the voltage directly at the alternator to be 13.65V. But this is only partly true, because i measured ground at the engine and not at the alt.

So when i removed the alt i found out that the bolt that also works as the ground connection was a little bit loose and hat some oxidized spots on it. So i cleaned it and put it back in, and now the charging current has about doubled. With a cold alt, i can measure 14V directly on it (now also measuring ground at the alternator housing), which goes down to about 13,9V when hot.

Charging currents start at 90A with the battery bank at 70% and then go down to about 45A at 80%.

Vetus mounted the alt positive to the starter post with quite thin AWG5 cabling (why the hell do they do that with a 110A alt???), and the connection from there to to the main switch is some meters of 2/0 cabling so i get about 0,4V of loss from the alt through the main switch through the main fuse to the house batteries.

Thinking about adding a second 2/0 cable from the alternator directly to the house bank fuses to get even more charge current, but i'm not sure if this won't burn the alt down. Probably i should get some temperature readings before doing this.

[txg]

I discharged my bank again, this time to 50% using a hairdryer.

Then stopped discharigng and ran another test, engine at normal cruising revolutions (1500 rpm) in neutral and attached a temperature probe to the housing of the alt.

Charging started at 90A and went down slowly to about 70A when i stopped the test, because the alternator reached 135 deg C. Obviously this is too hot, because the shrink tube of the stock positive output cable started melting.

I really can't believe this, this is a stock engine from 2015 with a stock alternator with stock regulator charging a quite small (220Ah) AGM bank that's only discharged to 50% and sitting in a quite big engine compartment and still i can't have it running like this without burning down the alt or probably even setting the whole boat on fire.

Yes, there is no direct forced air cooling for the alt but as far as a remember this wasn't requested in the installation instructions.

looks like i have to find a quick way to get a quite strong direct airflow to the alt without raising noise levels too much.