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rgleason · 28-10-2018, 05:45

Quote:

Originally Posted by deluxe68

Balmar AT-165, Yanmar 4JH2E, 400AH, no idea on airflow or max voltage.If you search the internet you will find lots of people unsatisfied with Balmar small case alternators. Mine overheats when putting out over 125 Amps, engine speed does not make a difference.

Thank you! I meant continuous amperage, and you answered 125a and that increasing engine speed did not make a difference.
Just a couple of more questions please?
1. Roughly, what engine rpm is the lowest that will output 125a in bulk charging mode?
2. Are you using serpentine pulleys & belt K6, J10? Balmar altmount?
3. What is the diameter of your large crank pulley and the diameter of your alternator pulley (measuring from the same respective locations for consistency).
4. Then we can figure out the ratio, and thus the speed of the alternator.
5. Does your engine room get very hot? Is there any forced venting?

PS: Maybe it is overheating and if you have an MC-614 with Alternator Temp sensor, the field current is dropped to protect the alternator? What temp does the engine area get to?

rgleason · 28-10-2018, 06:04

There are two other papers about using Mosfet

Passive Full-Wave MOSFET Rectfiers for Electromagnetic Harvesting
by Mehmet Yilmaz
www.metroplexalternator.com/uploads/1/5/2/8/15280940/charging_system_theory.pdf

Design and Evaluation of a 42 V Automotive Alternator with Integrated Switched-Mode Rectifier
www.rle.mit.edu/per/wp-content/uploads/2014/04/Tang-Design-and-Evaluation.pdf
====
"A vehicle alternator is only about 50-55% efficient at best, (That's where all the heat comes from, what a waste!) and when you take other losses into account it approaches only about 25% overall efficiency. If you are planning on using the alternator for any project use, you can consider changing to:

Schottky diodes,
FET based rectifiers
and/or raising the output voltage.

There is lots of material on 42 V DC systems, and you can get a quite normal car alternator to produce this voltage with new MCU based electronic controls. This increases the efficiency and output power capability considerably."

So I ask, why not increase to 24vdc Alternator and use LiFePo4 24v bank and a Victron Orion DC/DC step down converter for $100-150?

Are our alternators using Schottky Diodes or MosFETs for greater efficiency?
Has anyone noticed that 24vdc alternators put out less heat? (Keep in mind they don't start charging quite as soon, but the low amperage is deceptive, because you must double it to compare to 12vdc output.

rgleason · 28-10-2018, 06:30

Bingo
LM74670-Q1 from Texas Instruments
full or half bridge rectifier architectures for alternators.

www.ti.com/lit/ds/symlink/lm74670-q1.pdf

Quote:

The LM74670-Q1 is a controller device that can be used with an N-Channel MOSFET in full or half bridge rectifier architectures for alternators. It is designed to drive an external MOSFET to emulate an ideal diode. A unique advantage of this scheme is that it is not ground referenced, thus it has zero IQ.

The schottky diodes in full or half bridge rectifiers and alternators can be replaced with the LM74670-Q1solution to avoid forward conduction diode losses andproduce more efficient AC-DC converters.

The LM74670-Q1 controller provides a gate drive for external N-Channel MOSFET and a fast response internal comparator to pull-down the MOSFET Gate in the event of reverse polarity. This device can support an AC signal frequency up to 300Hz.

What is in your Alternator?

tanglewood · 28-10-2018, 07:37

Quote:

Originally Posted by rgleason

Since the heat and efficiency of the Diodes is the problem, I would like to know if there is a more efficient way of rectifying. I assume all these alternators are using full rectification and not half with a center tap.

Maybe it was in another thread that I mentioned this, but the diodes are only part of the heat problem, and probably the smaller problem.

The diodes generate heat proportional to the current. Heating is a fixed voltage drop, times the current.

But the bigger factor is heating in the stator windings since that grows as the square of the current. The windings are a fixed resistance with varying current, so heating is i^2 times R. So double the current and you quadruple the heating.

So there is benefit is remote mounting the diodes in getting that heat away from the rest of the alternator, and perhaps improving air flow at the same time. But you will still generator the same heat in the ER, though not concentrated in the alternator case.

So looking back at my earlier comments about running at a higher voltage, if you double the voltage, you halve the current for the same power output. That also cuts the diode heating in half, and reduces the stator heating by a factor of 4. Now it's much easier to keep the alternator cool.

john61ct · 28-10-2018, 08:01

Some alts have much better fan design than others, internal vs external.

Make sure to get a design that matches your spin direction, or two-way.

Most work much better at higher rpm, contra-intuitive.

**a64pilot** · 28-10-2018, 08:03

It would seem that running a very high voltage alternator, that you have to some extent reinvented the AC generator? especially if you decide to forego the diodes as they are both inefficient and generate large amounts of heat.

Not picking on the idea, just seems that a lot of use cases seem to favor a Commercial off the shelf AC generator.

deluxe68 · 28-10-2018, 08:14

Quote:

Originally Posted by rgleason

Thank you! I meant continuous amperage, and you answered 125a and that increasing engine speed did not make a difference.
Just a couple of more questions please?
1. Roughly, what engine rpm is the lowest that will output 125a in bulk charging mode?
2. Are you using serpentine pulleys & belt K6, J10? Balmar altmount?
3. What is the diameter of your large crank pulley and the diameter of your alternator pulley (measuring from the same respective locations for consistency).
4. Then we can figure out the ratio, and thus the speed of the alternator.
5. Does your engine room get very hot? Is there any forced venting?

PS: Maybe it is overheating and if you have an MC-614 with Alternator Temp sensor, the field current is dropped to protect the alternator? What temp does the engine area get to?

1. No idea, but you could probably find it on the Balmar web site.
2. Yes, Balmar.
3. No idea.
4. See #3
5. Have not measured area temp, exhaust fan pulls from the bilge below the engine.

tanglewood · 28-10-2018, 09:03

Quote:

Originally Posted by a64pilot

It would seem that running a very high voltage alternator, that you have to some extent reinvented the AC generator? especially if you decide to forego the diodes as they are both inefficient and generate large amounts of heat.

Not picking on the idea, just seems that a lot of use cases seem to favor a Commercial off the shelf AC generator.

I totally agree. For larger loads just running a generator consumes less fuel and generates less heat that needs to be disposed of.

But some people don't have or don't want generators, or have an aversion to running them

**newhaul** · 28-10-2018, 09:32

Quote:

Originally Posted by tanglewood

I totally agree. For larger loads just running a generator consumes less fuel and generates less heat that needs to be disposed of.

But some people don't have or don't want generators, or have an aversion to running them

exactly my thinking .
Where on a 29 ft mono would one mount a diesel gen set. (Don't say honda portable. I am trying to get away from multiple fuels onboard )

rgleason · 28-10-2018, 10:35

Tanglewood
Thanks for clarifying the alternator heat issue.

Diode Rectifier heat linear (1.2w/amp for .6v drop) = 6 diodes x 1.2w/amp x 140amp= 1008w= 3500 btuh (Is this right? It feels too big. Are all the diodes working 100%?)
Rotor and Stator heat is exponential = How to get a handle on that?

Certainly the remote rectifier could be improved with a "Smart High Efficiency Rectifier" using a Texas Instruments LM74670-q1 and Mosfet Rectifier which is completely detailed here

www.ti.com/lit/ds/symlink/lm74670-q1.pdf

What exactly would change with a generator?

Another complicated system.
Another engine.
More heat from generation.
Where on a 32' boat?

I started a thread called Tiny Powered Alternators & DC Generators - Cruisers & Sailing Forums
which was very informative, but I never really found an answer for me for the long tail on charging FLA until I found EFOY, but it was very expensive, another fuel and took some living space in a side locker.

So now I am trying to get a good alternator setup that really does work for a LiFePo4 Bank of between 200-300 ah that will charge quickly, not 3 hours, preferably not 2 hours. I will have about 50-100 watts of solar (max) to ensure the LiFePo are maintained at about SoC60% and to offset some daily use.

I'd like to have an alternator that fits in 3ym30 that will put out 130-140a continuous, if changing to 24v will help then maybe, if not, it is not worth it because the low rpm charge on the hook, scenario might suffer. I doubt that one of the Delco 24si (160a) or 28si (160a - better at low rpm than 200a) will fit, but I am going to certainly try. I kind of doubt those will achieve my goal anyway.
I've made these kinds of google searches to find a 12v Alternator Texas Instruments LM74670-q1 Mosfet Rectifier

Smart Mosfet Rectifier
High Efficiency Mosfet Rectifier
Alternator mosfet Rectifier

And I found these projects

You would think that these components would be off the shelf for 12v Alternators by now with Toyota, Nissan, Tesla, Gm and all the rest into EV. Maybe I am not looking in the right place or maybe the mosfets are not big enough or robust enough for 200a and just 16v

Quote:

Ideal Diode Bridge Analog Devices' ideal diode bridge controllers replace the four diodes in a full-wave bridge rectifier with a low loss MOSFET to drastically reduce power dissipation, heat generation, and voltage drop.

The Schottky diode bridge rectifier is a classic circuit used for full-wave ac-to-dc rectification and dc polarity correction. Due to the ~0.6 V drop of each diode, the two diodes in the I/O path dissipate power (1.2 W per ampere), radiate heat, raise the ambient temperature, and complicate thermal design.

At low input voltages, the two diode drops significantly reduce the voltage available to the downstream dc-to-dc converter.

Ideal diode bridges eliminate or reduce heat sinking requirements, which helps shrink the overall footprint and provides significant cost savings.

https://www.analog.com/en/technical-...techclips.html
https://www.powerelectronics.com/pmi...dge-controller

**a64pilot** · 28-10-2018, 10:35

Why not a Honda portable?
What’s the big deal about multiple fuels?
I mean really, is a gas can or two on deck really that big a deal?
A little Honda, all in is $1,000, total. Nothing else to buy, nothing to modify etc, doesn’t add any heat in the boat, and puts zero hours on the main propulsion motor, but will provide all the power you need. It will charge the bank, run a small AC if that’s your thing, run a Watermaker etc.
Just not all at once.

2KW of power for 1 grand is tough to beat.

rgleason · 28-10-2018, 10:59

Ha, look at this search on 12v "Mosfet Regulator" well actually these are regulator and rectifier combined, for motorcycles.
https://www.amazon.com/mosfet-voltag...tage+regulator
Not quite what we want, but not too far from it!
We need multi step regulation and user control over parameters.

rgleason · 28-10-2018, 11:02

Quote:

Originally Posted by a64pilot

Why not a Honda portable?
What’s the big deal about multiple fuels?
I mean really, is a gas can or two on deck really that big a deal?
A little Honda, all in is $1,000, total. Nothing else to buy, nothing to modify etc, doesn’t add any heat in the boat, and puts zero hours on the main propulsion motor, but will provide all the power you need. It will charge the bank, run a small AC if that’s your thing, run a Watermaker etc.
Just not all at once.

2KW of power for 1 grand is tough to beat.

I think I would stretch for the EFOY because it integrates better and would automatically backup the LiFePo4, and is quieter than the Honda, although I understand the honda is quiet. less concern running it (honda at sea outside)

**newhaul** · 28-10-2018, 11:03

Quote:

Originally Posted by a64pilot

Why not a Honda portable?
What’s the big deal about multiple fuels?
I mean really, is a gas can or two on deck really that big a deal?
A little Honda, all in is $1,000, total. Nothing else to buy, nothing to modify etc, doesn’t add any heat in the boat, and puts zero hours on the main propulsion motor, but will provide all the power you need. It will charge the bank, run a small AC if that’s your thing, run a Watermaker etc.
Just not all at once.

2KW of power for 1 grand is tough to beat.

everything on my boat is 12 volt except the television and DVD player and they can run off a 400 watt inverter easily. So why carry additional fuels if not needed . Aside from the solar onboard engine will be a backup charge source . The faster I charge my Lfp the better ( md2b at 20 HP ) when using the iron wind.