Is there such thing as goin tooooo big on my alternator upgrade?

[Ya Ubetcha]

For example the Perkins 4-108 has 4 cylinders and 3 main bearings. One at each end and one in the middle. The crank is not supported between rod bearings 1 and 2 or 3 and 4. A side load at the end from a large alternator will put a compression load on one side of the shaft and an opposite tension load on the other. As the shaft turns, these loads essentially rotate around the shaft. Given the unsupported areas between the two end rod bearings a slight jump-rope deflection can develop. This is in addition to the rotating compression/tension. An engine with 5 main bearings would be less susceptible. Engines need to be designed for large crankshaft side-loads. Engines designers expect a certain amount of side-load for auxiliary equipment such as alternators. Some of the new high power alternators may exceed the expectations for older engines. When pushing the limits one must consider such things. Any shaft bending on machinery is a major contributor to failure because of the rotational energy especially at higher speeds.

[Q Xopa]

Originally Posted by Ya Ubetcha

For example the Perkins 4-108 has 4 cylinders and 3 main bearings. One at each end and one in the middle. The crank is not supported between rod bearings 1 and 2 or 3 and 4. A side load at the end from a large alternator will put a compression load on one side of the shaft and an opposite tension load on the other. As the shaft turns, these loads essentially rotate around the shaft. Given the unsupported areas between the two end rod bearings a slight jump-rope deflection can develop. This is in addition to the rotating compression/tension. An engine with 5 main bearings would be less susceptible. Engines need to be designed for large crankshaft side-loads. Engines designers expect a certain amount of side-load for auxiliary equipment such as alternators. Some of the new high power alternators may exceed the expectations for older engines. When pushing the limits one must consider such things. Any shaft bending on machinery is a major contributor to failure because of the rotational energy especially at higher speeds.

Not arguing with any of what you are saying. All sounds reasonable to me.

Firstly how much of an issue actually is it? Do you know of any history of failures that could be attributed to this?

I agree with what you are saying but, it is a question of degrees. Of course there is a load on the Crankshaft.

I'm pretty sure cinching up the Alternator belt, pulling up on the crankshaft, is a lot less force on the Crankshaft than pistons getting exploded downwards and rapid changes in directions.

Secondly, with Serpentine belts obviously have more grip so generally have less tension required. This is easier on water pump bearings and as is being mentioned crankshaft side loads.

So with High output Alternators with Serpentine belts there is generally less Crankshaft side loading.

But I could be wrong.

[skipperpete]

Originally Posted by Sidney777

Maybe I missed it, but how many hp does high output alternator Take from your Engine ?

Balmar guide says 1 hp for every 25 amps so 8.5 hp for OPs 215 amp plan. A 4JH series Yanmar has a max front crankshaft load of 8 hp @ 3,800rpm so possibly the 3GM front journal is somewhat less than this. I was unable to find data for the 3GM but here’s the 4JH.

[a64pilot]

Originally Posted by skipperpete

Balmar guide says 1 hp for every 25 amps so 8.5 hp for OPs 215 amp plan. A 4JH series Yanmar has a max front crankshaft load of 8 hp @ 3,800rpm so possibly the 3GM front journal is somewhat less than this. I was unable to find data for the 3GM but here’s the 4JH. Attachment 208530

I doubt that 1 HP per 25 amps includes belt losses, which aren’t insignificant, in other words I believe that the actual load may be even higher than that.
I remember reading decades ago that a belt on a pulley turning nothing cost 3 HP to run at highway speeds don’t know if it’s true or not.
I believe a serpentine is more efficient as it’s more flexible.
1 HP per 25W assuming 14V is 350 watts, which is I believe about the efficiency of an alternator, perfect world no losses 1 HP is 750W I think.

That is an issue with using amps that I don’t like, the power varies with voltage where it doesn’t with wattage, so if your a manufacturer and use amps, you can play with the numbers a little by varying volts if you choose to, not saying Balmar does, but they could.
25 amps at 12V is 300W and 25 amps at 15V is 375 for example.

Also very relevant I believe is using the chart you supplied the allowable HP draw at a more normal cruising speed of 2500 RPM is less than 5 HP, and if you going to run your engine at anchor to charge batteries, it’s much less than that. 1000 RPM is less than 1 HP and even 1500 it’s what 2HP?

[Michael Cobbe]

with a 300ah lithium bank this week.



Lithium batteres have caused fires in planes and cars. https://www.thoughtco.com/why-lithiu...ch-fire-606814

[GordMay]

Greetings and belated welcome aboard the CF, tommo, and philm.

Originally Posted by Sidney777

Maybe I missed it, but how many hp does high output alternator Take from your Engine ?

An alternator typically takes about 1 HP (horse power) for every 25 amps of nominal 12VDC power generated, including belt losses.

[rom]

Originally Posted by skipperpete

Balmar guide says 1 hp for every 25 amps so 8.5 hp for OPs 215 amp plan. A 4JH series Yanmar has a max front crankshaft load of 8 hp @ 3,800rpm so possibly the 3GM front journal is somewhat less than this. I was unable to find data for the 3GM but here’s the 4JH. Attachment 208530

Interesting ! So it seems there is no problem with the bearings of crankshaft and water pump or any other parts whatsoever, at least up to 8hp for the 4JH3 series. What is the name of this document ?

[a64pilot]

Originally Posted by rom

Interesting ! So it seems there is no problem with the bearings of crankshaft and water pump or any other parts whatsoever, at least up to 8hp for the 4JH3 series. What is the name of this document ?

Look at the chart, it’s only 8 hp at redline RPM, it’s a straight line decrease from there. What I would call a normal cruise, which is high for me of 2500 RPM, you can draw less than 5 hp.
So, about 100ish amps, leaving a little safety factor?
It’s also with an overhang of 44 mm, which I assume is a stock and not an additional add on pulley, I also assume what is calling the crankshaft pulley isn’t a pulley but the harmonic balancer, I make that assumption from the depicted viscous coupling.

What isn’t answered is if it were two alternators 180 opposite of each other, can you draw considerably more power?

I have an older 4JHE which I don’t believe has this chart, but I believe it’s straight out of the engine manual

[a64pilot]

Originally Posted by GordMay

Greetings and belated welcome aboard the CF, tommo, and philm.


An alternator typically takes about 1 HP (horse power) for every 25 amps of nominal 12VDC power generated, including belt losses.

I don’t think it does, and this is why. First you find that number quoted from other sources as well, I believe even Delco Remy, but it’s a very variable number if you really start looking, small frame alts are roughly about 50% efficient where School Bus alts are up as high as 65%
The other big efficiency hit is from higher outputs, at high outputs they lose efficiency.

Anyway if you use 750W as 1 HP and a voltage of 14, the automotive norm and 50% as efficiency you will get to that 25 amps.
Either way belt losses aren’t as high as I thought, so it’s sort of irrelevant, shows what happens when you go from memory from decades ago. I was maybe thinking about old fashioned radiator fans.

However I did some looking and serpentine belts are very efficient, very. So much so that for practicable purposes I’d say those losses can be ignored.
V belts are about 93% efficient in use and serpentine is about 98%
5% may not sound like much but it adds up.
Go to a school bus alternator and serpentine drive and you gain 20%, I assume that hold true for most large frame alts too?

This is a good white paper, it goes after alternator efficiency from a fuel savings perspective and is really about larger trucks, but it’s applicable.
http://www.delcoremy.com/documents/h...ite-paper.aspx

[skipperpete]

Originally Posted by rom

Interesting ! So it seems there is no problem with the bearings of crankshaft and water pump or any other parts whatsoever, at least up to 8hp for the 4JH3 series. What is the name of this document ?

This is from the yanmar bible, the complete installation and engine tech specs from 1GM to 6CXseries

[skipperpete]

Originally Posted by a64pilot

Look at the chart, it’s only 8 hp at redline RPM, it’s a straight line decrease from there. What I would call a normal cruise, which is high for me of 2500 RPM, you can draw less than 5 hp.
So, about 100ish amps, leaving a little safety factor?
It’s also with an overhang of 44 mm, which I assume is a stock and not an additional add on pulley, I also assume what is calling the crankshaft pulley isn’t a pulley but the harmonic balancer, I make that assumption from the depicted viscous coupling.

What isn’t answered is if it were two alternators 180 opposite of each other, can you draw considerably more power?

I have an older 4JHE which I don’t believe has this chart, but I believe it’s straight out of the engine manual

There is a seperate section devoted to how to safely extract maximum hp from the pulley end of the crankshaft, with the alternator as installed on the 3GM30 ( called “A” position) 6 hp is possible but as you spotted , belt drag and other loads must be considered and yes, the figure is for max rpm.

[GordMay]

Even the most simplistic approach for contemplating overall Generating Set efficiency quickly identifies the reciprocating internal combustion engine as being the most inefficient component.
According to http://www.delcoremy.com/documents/h...ite-paper.aspx
“... With a typical ENGINE efficiency of 40%, a belt efficiency of 98% and an alternator efficiency of 55%, this leads to an OVERALL energy conversion efficiency of only 21%...”


Subtracting the engine efficiency leads to an ALTERNATOR efficiency of 54% (0.439 x 750 = 404W, or about 28A/HP).

ALTERNATOR efficiency should describe how effectively an alternator uses horsepower from the engine, to convert mechanical energy to electrical energy, that is then used to charge the batteries.
Efficiency is the ratio of electrical power out of the alternator, to the mechanical power put into it, and is usually expressed as a percentage.

Both the NEMA and IEC standards allow efficiency to be measured by an indirect method. This is also known as summation of losses measurement. Instead of measuring power in and out of the machine, separate tests are used to quantify the five types of losses in the generator. These losses can be categorised into fixed losses and variable losses.

Fixed losses are independent of load. There are two:
- Friction and windage losses typically represent 10% of the alternator’s total losses. These are losses due to the bearings, fans or blowers and the rotor itself. Optimising the fan design is the best way to reduce these losses.
- Core losses typically represent 12% of the alternator’s total losses. These are losses caused by hysteresis (a magnetic ‘friction’ caused by the alternating magnetic flux flow) and eddy currents (induced electrical currents). Core losses can be reduced by using a better grade of lamination steel or modifying the alternator design to operate at a lower magnetisation level. The latter method, however, affects the generator’s ability to handle reactive loads.

Variable losses are dependent on load. There are three:
- Stray load losses typically represent 12% of the alternator’s total losses. These are losses caused by the load current due to changes in the magnetic flux distribution, eddy currents and harmonics. They can be reduced by using better materials and thinner laminations.
- I2R losses in the armature and field typically represent 63% of the alternator’s total losses. These heat losses are due to resistance in the windings and can be reduced by using more copper or by running at cooler temperatures.
- Brushless exciter losses typically represent 3% of the alternator’s total losses. These are small loses due to electrical energy going into the exciter and rectifier.

[a64pilot]

Yes, but you can’t do anything about efficiency of an engine, not that I’m aware of.
Secondly a small frame alt is particularly inefficient, why this matters is based on the available horsepower draw that you can safely pull off of the front of the crankshaft.

What is all evolves down to is that about all you can safely pull from the AVERAGE cruising boat motor is at an average cruise RPM is about 100 amps.
Having said that, it’s my opinion that’s about all you can continuously get out of a small frame alternator without running it so hot that you reduce its life.
At 1800 RPM all I get is about 90 amps, however I have my temp set very conservatively, I believe if I allowed higher temps of course I could get more, how much? Not sure but likely not much more than 100 amps, which it seems pretty much maxes out my 4JH anyway.

What is the relevance of this and why have I posted so much about it?
It’s my opinion that 200+ amp small frame alternators are sort of a fantasy, they are like dirt bike motors, capable of huge outputs, but not for very long.
A farm tractor and a dirt bike may both make 50 HP, but your not plowing a field with a dirt bike motor, and it’s not torque either that’s another myth, HP and torque are inseparable.
These alternators aren’t cheap either, it’s easy to dump $2,000 or more into a big alternator what with the belt kit and external regulator added into the price of the alternator.

The idea of I’ll buy a huge alternator and charge my xxx AH Lithium battery bank up with only an hour or two at anchor at high idle is often proposed on this forum.
There is nothing wrong with doing it either, just go into it with realistic numbers is all, you can’t actually put 200+ AH into a Lithium bank in an hour, for many reasons, at least not from a small frame, crankshaft driven alternator.

To make that kind of power in my opinion your looking at a standalone generator, or if your desire to use your propulsion motor, you need to find one with a PTO that’s designed to draw a significant amount of power from it.

It’s sort of similar to the people who think they can run air conditioning or propel their boat from Solar power, they want to use the rated output of the Solar panels to work their figures, and unfortunately you don’t often get full rated power from panels, and when you do it’s only for a short time.

Alternators are similar, you just don’t get that kind of power for very long, and if you did, you exceed most engines capability.

[jmh2002]

Originally Posted by sy_gilana

If you want the ultimate alternator, look no further than the Delstar Series 180 brushless alternators. Nearly 500 A out of some of them, they will outlast any other by a long way. web page is www.dixie-electric.com
If I had spare cash to throw at my engine, it would be one of these, and a Davco filter.
There are better things out there than Balmar and Racor.

I agree that there are better things out there than Balmar and Racor.

Looking for some ultimate alternators? Let's bring out the big guns:

Electrodyne | Brushless Automotive Alternators

These cost a pretty penny but are the real deal.

[a64pilot]

Now. You can spend lots more money and remote mount your diodes and get more power from a small frame alt cause your removing a big source of the heat, but your likely better to start with a large frame one.