Running Two Alternators

[s/v Jedi]

Journeyman,

I don't understand that. Alternator output is dependent on alternator rpm's, not engine rpm's. If you want more output at low engine rpm you just change the pulley ratio.

Each of my Lestec 210's produce 175A in the tropics. I have seen 200A in Florida when temperatures were down (cold front).

I don't have numbers for different rpm's because I try to never use the system; it's just a back-up for us. Simply get the alternator output graph and you will find the rpm's you need for your desired output. Compare that to the engine rpm's you want to run at and there you have your pulley ratios.

p.s. we use single NAPA V-belts on these without trouble!

edit: you must of course make sure that you don't go over maximum alternator rpm's at higher engine rpm's. If that is not possible, you will have to switch the regulator off during motoring.

ciao!
Nick.

[Journeyman]

Nick,

I plan to use a 2.5:1 ratio, any higher ratio and there is not enough wrap around the pulley to maintain traction.

I pulled up the specs on a Penntex (acquired Lestek?) PS-328s alternator and they indeed show 175A/3,000 rpm alternator/200 deg F. I think this is today's equivalent of your alternators.

While the Balmar 210A I have been looking at, is roughly the same weight and case size, but only 115A/3,000 rpm alternator/190 deg F.

What gives? Your "school bus" alternators put out almost 50% more amps than Balmar's "marine" equivalent.

And since they both must operate in enviroments of sea water (road salt and rain), hot temperatures, and vibration, what makes them more "marine" than Penntex in diesel applications?

You say you rarely use them, but do you think yours could sustain a constant 175A hot output, for an hour, into a deeply discharged battery bank (think infinitely high charge acceptance).

I find it very interesting that you can get 175-200A with no belt squeal or adverse effects on a single V belt.

Thanks,

Journeyman

[goboatingnow]

Having studied LiFeP04 in a marine environment I don't beleive that a BMS is strictly neccessary. With a standard regulator HVC events will not occurr and LVC events could simply be manually monitored just like we do for lead acids.

[hellosailor]

Journeyman-
"Marine" alternators often are ingition-protected by installing screening to prevent sparks from igniting fuel vapors. Not a consideration on diesel busses, but it reduces airflow and causes heat buildup. Similarly, they may have coatings to prevent aluminum parts from corroding--more heat buildup. Or they may just have that "Hey, here's a guy with disposable income!" factor added to them.
The little things add up. Bus & truck alternators tend to be designed to carry large loads for long periods of time (all those lights, heaters, etc.) and size is usually not an issue, so they can be built differently from "auto" alternators. I'd also expect them to be targeted to a smaller speed range, compared to auto alternators (which sometimes have to deal with engines running 800-8000 RPM, a much wider range than trucks or busses usually cover).

[Laidback]

A feature of the Westerbeke 65A engine is that it has to run at Full throttle of 2,600 RPM to achieve its rated prop shaft HP. If one runs it at a comfortable 1,700 RPM then it only produces 20HP - minus the combined power requirements of 2 large alternators = equals slow boat.

[Journeyman]

Originally Posted by hellosailor

Journeyman-
"Marine" alternators often are ingition-protected by installing screening to prevent sparks from igniting fuel vapors. Not a consideration on diesel busses, but it reduces airflow and causes heat buildup. Similarly, they may have coatings to prevent aluminum parts from corroding--more heat buildup. Or they may just have that "Hey, here's a guy with disposable income!" factor added to them.
The little things add up. Bus & truck alternators tend to be designed to carry large loads for long periods of time (all those lights, heaters, etc.) and size is usually not an issue, so they can be built differently from "auto" alternators. I'd also expect them to be targeted to a smaller speed range, compared to auto alternators (which sometimes have to deal with engines running 800-8000 RPM, a much wider range than trucks or busses usually cover).

Sailorman,

So Sparks, Size, and Speed are the "marine" vs "truck" alternator differences.

What about the voltage regulator? S/V Jedi's post has me thinking to buy the Penntek 328S but I notice it comes with an external PX-400 Regulator. If I use an external "marine" programable regulator, will I get the speced output? Or is it likely the supplied alternator some how optimizes the alt output in a way say a Balmar Dual cannot?


Many Thanks,
Journeyman

[s/v Jedi]

Originally Posted by Journeyman

You say you rarely use them, but do you think yours could sustain a constant 175A hot output, for an hour, into a deeply discharged battery bank (think infinitely high charge acceptance).

I find it very interesting that you can get 175-200A with no belt squeal or adverse effects on a single V belt.

They do sustain 175A after starting higher at 200A each. I don't know but heard that Balmar acquired Lestec? Anyway, here's one of them on Jedi:


ciao!
Nick.

[hellosailor]

"thinking to buy the Penntek 328S but I notice it comes with an external PX-400 Regulator. If I use an external "marine" programable regulator, will I get the speced output? "
If I read you correctly, the Pentek comes with a programable external regulator and you want to know if using a different "marine" external regulator will affect the output?

It certainly could. You'd have to find out how each regulator was programmed, to find out if they can deliver the same performance. Odds are that as long as they are designed for deep cycle batteries, and have the same intelligence onboard, they both would work well. Some regulators are 3-stage, some claim 4- or 5-stage ("off" being the fifth stage, duh)...some use more sophisticated logic than others but as long as they can tell the alternator "full speed ahead" they both should give you similar performance.

[Journeyman]

Guys,

I just read the manual on the Balmar MC-612-DUAL regulator.

It has no knowledge of the manufacturer, or the output capacity, of the alternator it is regulating.

It runs open loop in the standard installation (no temperature sensors).

Simply senses the battery voltage and trys to establish a constant voltage during bulk charging for the battery chemistry you select.

In other words, it just provides its "maximum field potential" during the time the voltage is coming up to its set point.

Does that mean these things are designed to provide the same excitation voltage to a 50A alternator rotor as it would to 350A alternator rotor???

And that the native resistance of the rotor winding is used to limit the rotor current?

That is, big alternators would have lower resistance, and take alot more current?

But then, why don't they spec what the upper limit is on the current the regulator can provide?

In short, how does the customer know whether the regulator is capable of providing enough rotor current to match your big alternator?

Or do they just assume you won't notice any passive underperformance by a big alternator?


Thanks for any input,

Journeyman

[hellosailor]

Excellent questions and perhaps you could get Balmar on the phone to answer them.

I see one other point to be concrened with: Heat! If the external regulator is capable of simply applying full field coil excitation, with no knowledge of how hot the alternator is, and the alternator itself has no means to throttle itself back when/if IT senses it is getting too hot...This regulator has the potential to cook the alternator, which probably is NOT rated for 100% duty operation for long periods of time.

One or the other (regulator or alternator) has to be able to sense the temperature on the diode frame and reduce output when the diodes are overheating, unless the system has other means of preventing that. (Like massive overcooling, so it simply can't get that hot, even on midsummer day in the desert with the vents all closed.)

The good news is, Balmar usually and eventually answers the phone, except when they're all off to a boat show for a week. (Literally.)

[S&S]

Originally Posted by Laidback

A feature of the Westerbeke 65A engine is that it has to run at Full throttle of 2,600 RPM to achieve its rated prop shaft HP. If one runs it at a comfortable 1,700 RPM then it only produces 20HP - minus the combined power requirements of 2 large alternators = equals slow boat.

That's why I went with the Beta 75.

[isobelk]

balmar regulators have optional connectors for temperature probes for both the alternator and the battery bank being charged. If either gets too hot, the regulator will shut things down.

[isobelk]

Incidentally, I run a Penntex PX-3s-200 (200A) to recharge my 1600ah AGM bank. The alternator is driven via a serpentine belt. I use a Balmar ARS-5 regulator which is completely programable to the particular bulk, absorb, float voltages the battery mfg specs. I also use the temp probes on both the alternator and battery bank.

Balmar Digital Duo for the start batt. recharge.

My boat is a trawler, so we have a motor running to spin the alternator every time we move the boat.

I have purposely set the regulator to never use all 200 amps of the alternator - it is set for a 170A max.

On a 25% discharged bank, the alternator will put out 170A for a couple of hours, then as it cycles into absorb and float it will gradually work its way down. I can usually fully recharge in about 4 hours, although I am at 95% in about 2 hrs.

I will periodically check the temp of the alternator with an IR and it is usually around 160 degrees, even when putting out 170A

Happy with the Penntex large frame alternator - I used to run a small frame souped up to 140A - but it really got hot and realistically never put out much more than 100A for any length of time.

[Journeyman]

On a 25% discharged bank, the alternator will put out 170A for a couple of hours, then as it cycles into absorb and float it will gradually work its way down. I can usually fully recharge in about 4 hours, although I am at 95% in about 2 hrs.

I will periodically check the temp of the alternator with an IR and it is usually around 160 degrees, even when putting out 170A

Happy with the Penntex large frame alternator - I used to run a small frame souped up to 140A - but it really got hot and realistically never put out much more than 100A for any length of time.[/QUOTE]

What engine rpm gives the continuous 170A (I'll assume your alt rotor is spinning at twice that)?

I guess it is just impossible to design a small case alternator that can put out more than 100A for 30 mins, at 3,000 rotor rpm and below. Did you ever put your IR thermometer on the 140A small case when it was running?

[isobelk]

on my motor - Cummins 5.9 - full output when over 1200 rpm.

did not have the IR thermometer at the time of the small case alternator.