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Old 18-06-2018, 17:25   #1
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Alternator choices

Currently on my Perkins 4.236 I am running a Balmar 91 series 100 amp alternator. I also have a Hehr 23-12m spare alt which gives pretty much the same output as the Balmar. They are both based on (as far as I know) the Delco 10 DN style case.

These alternators are OK and give around 70 to 80 amps into the LiFePO4 house bank and appear to be able to run without overheating for some time.

I am using Balmar MC-612 regulator.

In my quest to increase the charge capabilities from the engine I've been looking at adding a new higher output alternator and selling one or both of the 100 amp units.

I look at the Balmar hairpin wound units and think about that (and what spares to carry) and other options too.

Right now I am toying with a CS144 alternator. 200 amp units are available at a very reasonable cost. And rebuild kits are also quite reasonable.

I only intend to run the alternator at about 120 amp output and both the AT-165, AT-200, CS144 would do that day in and day out.

But, I am drawn to the idea that I could get a CS144 and a full rebuild kit for less than half the cost of the Balmar AT-165.

I'm tempted to head to a junkyard and pull a CS144 out of a wreak just to see how well it would fit on the engine. A used alternator would give me a chance to see what was involved in converting the CS144 to external regulation and a chance to rebuild one.

Anybody using a CS144? Are you using external regulation (whos conversion parts), How about external rectifiers?

Regards!
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Old 18-06-2018, 18:30   #2
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Alternator choices

Common swap in the automotive world, but its not really a large frame alt, which is what you need.
Just me, but Im not so sure that those very high output Balmar and others alternators can do so continuously, I donít think the cooling is there to support that kind of output myself.
Iíd call Mark Grasser and ask him what he thought.

External rectifiers will of course help, pretty sure Maine Sail has done some testing there. Maybe he will chime in
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Old 19-06-2018, 06:24   #3
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Re: Alternator choices

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Originally Posted by evm1024 View Post
....But, I am drawn to the idea that I could get a CS144 and a full rebuild kit for less than half the cost of the Balmar AT-165.....
You do get what you pay for in life, especially with marine kit that seems to be very expensive, but a CS144 is just a heavy duty automotive alternator. I have the Balmar 100 amp Series 6 with ARS5 and spares, and I was looking at the dual mounting pulley kits to double the capacity and then derate them to say 80% each.

But let me give you my thoughts on why Balmar kit is worth it - by the way this is above learner 101 grade - for most people. The last time I posted this I was accused of copying and pasting it. YES I did copy and paste this - from my own book yet to be published.

Marine Alternators

A car alternator is engineered to a price - cheap - because its main job is to charge a starter battery that has been discharged by about 1%, or about 1Ah, which it can do in about 10 minutes. Then it just has to supply power to the car systems. A 60 amp alternator can happily do this job, even when it gets hot, when it's maximum output may have been reduced to about 30 amps.

 On a boat the load on the alternator to charge a 50% depleted 400 Ah bank will be much higher for much longer. 200 Ah will have to replaced in the bank, so it will be trying to supply near its maximum current for a long time and and supply the boat loads as well, so it will get hotter and hotter until its output may fall even further.

A hot rated 'Marine Alternator' like the Balmar is 'engineered' to better provide its rated output current even at a temperature of around 80-90 degrees C, so it will try to maintain that output and charge the bank much quicker. Faster charging is what we all want.

But remember under full load and in a small engine room even a hot rated alternator may go above 100 degrees C and its output current will be reduced by 50% by the external Balmar regulator - but its charging voltage will remain the same.

So ďMarine RatedĒ alternators may mean:



- High temperature diodes mounted on big heat sinks

- Heavier gauge stator windings

- Precision balanced rotor

- Copper composite brushes

- Heavy duty bearings with high temperature grease

- Corrosion resistant materials & coatings

- Dual cooling fans

- Access to field windings and external regulation

- Tachometer output

- Maybe an isolated ground terminal



So all this has to come at a much higher price!
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Old 19-06-2018, 07:12   #4
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Re: Alternator choices

Many sailors do just fine with the much lower cost HD truck alts, coupled with a good external VR.

Much easier to get serviced in primitive locations.

But for continuous output of half the max rating or higher, large frame and great ventilation are key.

Best of course is large frame *and* "marinized" but very pricey.
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Old 19-06-2018, 07:35   #5
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Re: Alternator choices

You reduce the current and voltage will go with it. Itís sort of like reducing power to your engine when your motoring, reduce power, and speed follows.
You canít charge a battery at 100 amps at 14 V and then charge it at 14 V at 10 amps. You can supply 14V, but the bank wonít be 14V.
Why? Because voltage is pressure, it takes X pressure to raise a banks voltage to a certain amount, reduce the pressure and you reduce the banks voltage, increase it and the banks voltage goes up.
That is why in bulk you have an ever increasing voltage but stable current, and in absorption you have stable voltage and ever decreasing current.
If you could change current and keep voltage the same, well then why do we not charge at max current in absorption?

These are voltage, not current regulators.

However what I really want to know, and have never seen is what it the max continuous power output of these high power small frame alternators?
I strongly suspect that the 200 amp alternator cannot continuously supply twice the current as a 100 amp alternator, and at some point there is rather large diminishing returns. Of course they are marketed as 200 amp alternators etc.
I know my 165 amp, at a temp that I am comfortable at it will supply continuously only about 80ish amps. I suspect a 200 amp seeing as how itís ability to shed heat ought to be similar, and heat is the limiting factor, may not supply much more.
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Old 19-06-2018, 07:38   #6
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Re: Alternator choices

Heat is the enemy, if you want continuous high output, and we do. Then we need large frame alternators, or water cooled ones or maybe forced air cooled ones.
Jacking up the power output without significantly increasing the cooling may not be accomplishing a whole lot.
There may be a size of alternator that above which your not getting much more output, but you are paying a whole lot more $$$.
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Old 19-06-2018, 08:23   #7
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Re: Alternator choices

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You reduce the current and voltage will go with it
Ö
You canít charge a battery at 100 amps at 14 V and then charge it at 14 V at 10 amps. You can supply 14V, but the bank wonít be 14V.
The "bank voltage" - actually a combined voltage negotiated between the bank and charge source - is irrelevant to the charge process in those early stages (bulk).

The setpoint for the charge output regulation is simply what it is "striving" for before the CC/CV transition.

Once SoC has climbed, V is being regulated by the VR, and amps accepted by the batt is much lower than the maximum available from the charge source.

That "pressure" thing is just an analogy.

Raising current forces the combined voltage to hit the setpoint **much** faster, and at a much lower SoC level.

> That is why in bulk you have an ever increasing voltage but stable current

No, only true while the bank is capable of accepting the max output from the charge source.

Otherwise Bulk's "Constant Current" is a misnomer, amps actually vary a lot, resistance is reducing current acceptance as voltage climbs.


> If you could change current and keep voltage the same,

No if about it, just get an adjustable mains power supply and do it yourself

> well then why do we not charge at max current in absorption?

Again, a high-amp charge source has no role in current acceptance, it only makes current available. The bank is "deciding" the amps level to **pull** from the source.

> However what I really want to know, and have never seen is what it the max continuous power output of these high power small frame alternators?

If properly protected, depends on their heat buildup.

Usually well under half the max rating.

If the high-CAR bank is pulling too much without proper heat protections, they burn out in a matter of minutes.

> I strongly suspect that the 200 amp alternator cannot continuously supply twice the current as a 100 amp alternator, and at some point there is rather large diminishing returns.

That's why large frame alts designed for continuous high amps output are required, along with fancy external VRs.

**If** the bank's CAR will even draw the extra amps made available. LFP is really the way to properly make use of a proper HO setup.

With lead, only the first 20-30 minutes will, overall charge time to 100% Full is barely reduced.

> I suspect a 200 amp seeing as how itís ability to shed heat ought to be similar, and heat is the limiting factor, may not supply much more.

Absolutely.
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Old 19-06-2018, 08:26   #8
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Re: Alternator choices

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There may be a size of alternator that above which your not getting much more output, but you are paying a whole lot more $$$.
Yes, mostly up to the bank.

Needs a systems approach.

All the above goes for a genny / mains charger as well, adding multiple paralleled 120A chargers to normal, even large, lead banks, won't reduce charge times much at all.
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Old 19-06-2018, 08:55   #9
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Re: Alternator choices

I have a couple of 100 amp older Balmar (series 7 if I remember) one and a spare. Recently I added a CC temp controller and connected the output switch to the small engine input on the 612. 600 AH of house batteries (6 GC2s). The controller is set to drop to half output at 200 F and switch back to full output (typically around 80 amps) at 180 F. I was surprised just how fast the alt temp reached the 200 F mark but when you open the engine box it dropped like a rock. Didn't run it long in the open engine box mode (temp down but noise goes up) but this has me thinking about bringing some cooler air from the bilge to the alt. Could get it from the frig but that would be some kind of perpetual motion setup.
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Old 19-06-2018, 08:59   #10
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Alternator choices

See, I donít think itís about half rated output. Small frame alternators only.
I think an 80 amp alternator may be able to make close to rated power, a 165 about half or 80 ish, and what Iíd like to know is what is a 200 capable of? I suspect that continuously itís not much more than a 165, maybe around 100 amps is the best ďbuyĒ?
Itís really the LFP crowd that would get the most benefit out of a monster alternator, most of use lead acid guys not as much.

I think that of course a 200 amp alternator can make 200 amps, there is no lie, just the duty cycle isnít mentioned, and I think if itís what I think it is, not so many people would shell out the big $$$ for those big alternators.

See, I went to buy a big one myself, and was talked into a smaller one by the seller, basically telling me without getting into details that He would love to sell me a 200, he makes more profit off of one, but that I wouldnít be getting my moneyís worth.
Now I think I understand why
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Old 19-06-2018, 12:37   #11
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Re: Alternator choices

I'm hoping that we can keep the content level of this thread quite high and the R Squared factor (RSF) very low.....

For the sake of my sanity I tend to break alternators down into a number of types. These divisions may not be used by industry or by others...

Light Duty - General passenger car alternators and those marine alternators that are based on them. And of course small in size. Their output is severely limited by thermal dissipation factors.

Heavy Duty - These alternators are designed for more rigorous use. Heavy duty truck use and the like. They are still limited by thermal dissipation factors but have a much greater ability to supply heavy loads with a medium duty cycle.

Continuous Duty - 100% duty cycle at rated output is the definition of these alternators. Big, heavy and robust.

There are 3 thermal limits that play a major role in alternator operation (that I can see). The rectifier temp, the temp of the stator and the bearing temp.

We often talk about the alternator temperature as a limiting factor and it is.

Rectifier temp. The actual limit is specified by Tjmax (Temp, junction maximum) which is the maximum allowed temperature which the junction (in the chip) of the individual diodes in the rectifier can withstand. Exceed this and the diode will fail (plus or minus).

Heat is created at the junction in the diodes die and that heat has to move to the case of the diode which then moves to the heatsink and from there the heat goes to the cooling air flow and the case of the alternator. The point being that the junction temp is much higher than the diode case temp which is higher than the heat sink temp which is higher than the case temp.

Measuring the heatsink temp is better than measuring the case temp. Thermal inertia and other factors come into play. The case will be cooler, and at the beginning much cooler than the junction temp. Typical tjmax is 175 degree C for at lease one family of diodes commonly used in alternator rectifiers.

Of course using better air flow, higher heat conduction materials (copper rather than aluminum etc) will move the heat away from the junction faster and thus keep the Tj (temp junction) lower for any given dissipation.

Stator temp. As was alluded to above the actual temp at any given part of an alternator is a function of the heat going into that part (be it a diode junction or a stator winding) and the heat removed from that part.

Up to the point of magnetic saturation as you increase the magnetic field the resulting induced current flow will increase. This leads us to the resistance of the stators windings. We know that for any given resistance there will be a voltage drop through a wire and that this voltage drop gives us heat generation. For any given moment there is some current flowing through the stator at some voltage drop which shows up as current times voltage drop = watts of heat generation. The stator gets hot.

The wire of the stator uses enamel (paint) as its insulator. That enamel can burn off if the temperature rises too high.

Bearing temp. I do not have a good feel for this one. Low quality bearings with crappy grease will break down more quickly as compared to high quality bearings with good quality high temp bearing grease. I've never "spun" a bearing on an alt yet, but....

Basically what I am saying that the limits of power that we can get from an alternator are set in the real world mostly by the thermal limits of the alternator. And in theory ultimately set by the magnetic saturation points of the rotor and stator. Not that we get there.

The alternator generates heat in the rectifiers, in the windings and in the friction in the bearings and slip rings. This heat is removed by the cooling air flow which is more effective when the cooling air is cooler. Faster air flow, better heatsinks etc can all be factored together as a thermal transfer coefficient. The higher the better.


Moving on.....
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Old 19-06-2018, 13:00   #12
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Re: Alternator choices

I have difficulty understanding the obsession with high output alternators. The average boat uses 200 AHrs a day, which implies 400 AHr battery bank which in turn cannot (or should not) take much more than 100A charging current) and that is only for a brief period of time before you hit absorption.

Light duty automotive alternators are just fine in such an application, even if their output drops. I bet the difference in typical charging a 400AHr bank between a cheap 80A alternator and an expensive 165A bus alternator to be very small, may be less than an hour.

I can see the point in larger boats or if you are running the watermaker, a washing machine and an induction stove off the inverter while charging the batteries. How many boats do that?
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Old 19-06-2018, 13:34   #13
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Re: Alternator choices

Ohms law


I think that we sometimes forget that Ohm's Law is a law not a suggestion.

Because our batteries not pure resistors and our alternators are not pure sources (they have inductance etc) we end up with not linear curves of their internal resistances and such.

But with that said and understanding the limits thus we can make some observations.

Amps are easier to define than volts.....

An amp is the flow of 1 Coulomb per second. That's helpful. But we can define is in better terms. 1 coulomb is the electrical charge of 6.242^18 electrons (or protons but let's not go there) per second. And because an amp is 1 coulomb per second then an amp is the flow of 6.242^18 electrons per second.

So current is the number of electrons moving.

Voltage on the other hand is a way of expressing the (gross simplification) energy of each electron. We have seen this expressed in terms of water pressure but I like to look it as the difference in energy between a ping pong ball, a tennis ball and a cannon ball all going at the same speed. Hey, wait. Light has a constant speed and E=MC^2 - ping pong balls weigh less than cannon balls.

Resistance is easy to understand too. Big doorway, low resistance, lots of people get through in any given time. Small doorway, high resistance, fewer people get through at any given time.


Anyway - We do get lost in CC,CV charging modes.

CV is "easy" to understand. Our supply (charger, alternator, solar, etc) adjusts the supply of current as it monitors the voltage and then stops supplying more current when a set voltage is reached. The voltage is fixed and the current varies.

CC is tougher because we do not really use CC. We actually use a current limited supply. In true CC if we set the current to 1 amp and the resistance of the load was 1 meg ohm then we would need 1 million volts ....

In effect a current limited supply has an internal resistance such that E/V=R or volts / 100 amps = the supplies internal resistance.

So the actual voltage measured is the supplied current divided by the combined resistance of the source and the load (the battery).

As the battery's resistance goes up (as it becomes more fully charged) the supply voltage rises with a constant charge current. Ohms law prevails. at some point the voltage cannot go up any more due to physical limits or regulation limits and thus we enter CV. As the battery's SOC increases and the internal resistance rises the current must drop to balance ohm's law.

Again this is a gross glossing over what actually happens so don't get too hung up on details. Just follow how the supply and load interact and that ohms law is balanced always.

Helpful?
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Old 19-06-2018, 13:48   #14
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Re: Alternator choices

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I have difficulty understanding the obsession with high output alternators. The average boat uses 200 AHrs a day, which implies 400 AHr battery bank which in turn cannot (or should not) take much more than 100A charging current) and that is only for a brief period of time before you hit absorption.

Light duty automotive alternators are just fine in such an application, even if their output drops. I bet the difference in typical charging a 400AHr bank between a cheap 80A alternator and an expensive 165A bus alternator to be very small, may be less than an hour.

I can see the point in larger boats or if you are running the watermaker, a washing machine and an induction stove off the inverter while charging the batteries. How many boats do that?
Some people do have an obsession with high output alternators. Not me... And with respect neither your or my understanding of others desires, needs or obsessions matters.

In my case I have 700 AH of LiFePO4 in the house bank which can accept much more charge than I can throw at it (or want to throw at it).

If I were to use 200 AH/day then I would need to run a 100 amp alternator for 2 hours each day (assuming that I could actually get 100 amps out of it). Skip a day and we are up to 4 hours.

But with a 200 (real amps) amp alternator it is only 1 hour per day.

Still too much which is why Dog invented solar.
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Old 19-06-2018, 13:53   #15
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Re: Alternator choices

I think that we have a general idea that getting 80 amps is a real figure for the typical small case alt (Balmar 6 series) and that 120 amps from a hairpin would alt is doable.

For those who want to run 200 amps charging for extended periods then something like a school bus alternator would be in order.

For me I just do not have confidence that my existing alternator will be able to meet my needs for extended cruising. And I think that a school bus type alt is overkill and over budget.

Running a heavy duty alt at half capacity has a draw for me. And as a it of a DIY type taking something like the CS144 and using it has an appeal.
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