Alternator Curves

[edwardc]

Ed,
This graph is for the Arco 60050 which is listed on the API site as the same as their 55A as well as the Mando. What ratio are you using to calculate alternator RPM (necessary for the graph to be meaningful)?

Thanks Neil. I'm aware of the need to measure the ratio to calculate alternator speed, but haven't done it yet. In an old post, Hanley suggested that the stock pulleys provided about a 1.3:1 ratio. For my typical 2000 RPM cruising (I have a 2:1 V-drive), that would give me about 2600 RPM on the alternator, which should put me up in the 40-45 amp range, which is just about right for the bulk charging phase on my 192 Amp-Hour house bank.

The chart is half of what I'm looking for. The other half is the family of curves for various temperatures. I'm in the early stages of converting my MMI-purchased Mando 55 to external regulation, probably using one of the Balmar smart regulators (but that's not cast in stone). Alternator output falls off with temp, and too hot a temp will cook the alternator. I'm concerned about cooking the Mando by pushing it too hard for too long, as the smart regulators can be prone to do in the bulk charging phase. Some of the Balmar regulators include temperature sensing and limiting for the alternator temp.

I just replaced my two Dekka Group 31 Gel cells after 12 years of service, so I was very pleased with them, and went back in with another 2 Dekka Gr-31 gels. For the past 6 years, my pattern has been mostly day or weekend sails, with an occasional 1 or 2 week trip thrown in. So the bulk of the charging has been on shore power, with a 3-stage smart regulator properly programmed for Gel cells, and temperature compensated for the battery temp (very important for Gel Cells). Given the exceptional life I got, it seems to have worked properly.

This fall, my pattern will change drastically, as we head down the ICW from the Chesapeake to Florida. This will entail large amounts of motoring, so I want an alternator regulator that will properly switch to a float voltage when the batteries are charged, as gels are particularly susceptible to irreversible damage from overcharging.

But then once in Florida, we will be jumping over to the Bahamas, and spending up to 3 months over there, largely on the hook or sailing. For this, We will need an alternator regulator that does proper, temperature-compensated bulk and acceptance charging phases to minimize the amount of daily engine run time required to make up our daily power budget (consisting largely of the refrigeration) of about 60-70 Amp-Hours per day. According to my measurements made on our 1 or 2 week cruises, the existing internal regulator is taking about 4 hours of engine run time to bring the house bank from 50% state-of-Charge (SOC) to 80% SOC, which is roughly where the transition occurs from bulk charging to the slower acceptance phase. With a properly configured smart regulator, this time should be closer to 2 hrs, which will translate into a significant savings in fuel. But its going to have to be limited by the alternator temperature, hence the need to know the Mando Alt's temperature curves, or at least an equation for derating it by temperature.

...The problem I have run into with steep ratios, alternator to engine, is the load on the engine at start up (before the engine reaches operating temperature) can be substantial and makes me uncomfortable, which is why I abandoned 3:1 and went to 2:1. If someone could come up with a way to delay full amperage output until the engine is warmed up I would consider going back to the 3:1.

Hanley,

The higher-end Balmar external regulators incorporate both a start-up delay, and a ramp-up feature. But they're pricy.

[tac]

Time Delay Relays

The McMaster 77055K736 relay is rated for 1 amp at 120vac. For an alarm circuit this is satisfactory. However, field current ranges from zero to 5+ amps for most alternators (my 50 amp Paris-Rhone has a 5A field current at 50 amps output). That high a current should destroy a 1 amp relay.

[ndutton]

In an old post, Hanley suggested that the stock pulleys provided about a 1.3:1 ratio.

The 1.75:1 stock ratio I mentioned came from A-4 specifications found here.

I'm sure you've analyzed your needs down to the gnat's hair but if I were planning prolonged cruising away from the dock with refrigeration I'd be looking at solar for sure, perhaps an engine driven refrigeration compressor with holding plates like the BVI charter fleet used successfully way back when I was there. Their charter instructions called for one hour of daily engine run time and they kept up (batteries and refrigeration) just fine without solar and if my memory hasn't failed completely, this was well before 3 stage smart chargers were popular.

About Tac's amperage comment, I didn't consider the amperage specification of the time delay relay I referenced so thank you. However, I could not help but think about the perceived concern of alternator loads during warm up and their significance. Has anyone ever had a problem? Is this an automatic charging relay concern? With my Jurassic manual battery switch system I start and warm up on an isolated starting battery, switch over to the house bank when I am ready.

[hanleyclifford]

I'm sure you've analyzed your needs down to the gnat's hair but if I were planning prolonged cruising away from the dock with refrigeration I'd be looking at solar for sure, perhaps an engine driven refrigeration compressor with holding plates like the BVI charter fleet used successfully way back when I was there. Their charter instructions called for one hour of daily engine run time and they kept up (batteries and refrigeration) just fine without solar and if my memory hasn't failed completely, this was well before 3 stage smart chargers were popular.

About Tac's amperage comment, I didn't consider the amperage specification of the time delay relay I referenced so thank you. However, I could not help but think about the perceived concern of alternator loads during warm up and their significance. Has anyone ever had a problem? Is this an automatic charging relay concern? With my Jurassic manual battery switch system I start and warm up on an isolated starting battery, switch over to the house bank when I am ready.

For the moment that is exactly what I do also.

[hanleyclifford]

Generator?

Hoping this does not seem to be a thread hijacking.
Some time ago we talked about portable generators. The Honda inverter seeming to me the, or near the gold standard, Yamaha making a serious run at the top as well.
At the AC boat show I spoke to a hnda rep re the Honda 2000 inverter model and aked about how it works. The rep wasn't much help.

It seems to me that the gas powered engine spins a generator or alternator to produce something other than 120V, then this electric it fed into a an inverter which transforms the mystery voltage into 120V .

Also some time back we saw pictures of Hanley's atl. driven off a HUGE pully off the front of his engine. This got me thinking about a better way to produce AC than a generator.

Yesterday I was flushing my freshwater system with dish detergent to remove internal junk deposits that always form in freshwater systems. For at least 6 hours my boat sat at the dock purring away at 650 RPM (engine needs to run for my circulation system to be powered up. Im guessing (swag guess) that if I normally burn about 1 gal per hour, cruising under power at 1700 RPM that my fuel consumption at 650 should be about 1/3 of my cruising use. Very economical.

Thinking again of Hanley,s "big wheel" alt setup, and tossing in a 150 amp alt (?) driven at 650 X3 1950 RPM ( lets say 2000 rpm) I should have plenty of power to drive a 3000 watt inverter off the Alt alone.

Why would this not be as good or better than as $1000 inverter/genset?

It would be better, and it is better; but if you follow the thrust of this thread you can feel the pain in your front crankshaft bearing and valve train when the thing kicks in. For engine health a way must be found to mitigate.

[hanleyclifford]

The Long Term Objective

in my case is to be able to motor the ICW at around 2000 rpm with a 1700 watt toaster oven cooking supper while maintaining full batteries. If you don't have 2:1 reduction, don't even think about trying to produce that kind of juice. First things first.

[BadaBing]

Surprised I have not done so before but I just measured my acc. drive and alt wheels.
3.85" & 2.37. (these are outside measurements but I think the math will work regardless) That works out to 1- 1.63. I guess I could go a little smaller on the alt but the shop was troubled about slippage.

Anyway at 1500 RPM my alt it spinning at 2436 RPM At 1800 max cruising range 2,934. Of course with a heavy load on, it might not be able to reach 1800.

After posting my deleted question, (quoted by Hanley ) it occurred to me that when I want aux AC I really don't want to have Katherine or I working in the galley with the engine roaring along at 1500 rpm, to make toast and coffee. Actually the battery bank does a fine job of powering our small 120V needs alone and they seem to be completely, or nearly so, recharged in only a half hour to hour of running time. WE might need a little extra juice for the toaster oven.

I'm thinking that "for those special " occasions a less costly Generac will do just fine at $499. if needed at all. The spare 35 amp alt will serve well as a backup if necessary to keep us going, even though it cant meet our aux needs.

[hanleyclifford]

If you have room for that little generator, and have the ability to exhaust safely, and a place to store when not in use (or a way and place to mount it permanently where it can be fueled, started, and exhaust conveniently - that might be the way to go.

[tac]

Cruising with Refrigeration

I have the following setup:
House batteries: Two gp31 105AH AGM batteries in parallel
Start battery: One U1R 32AH flooded
Balmar 612 regulator for the house bank, with alternator temp sensor. Manual at http://www.balmar.net/wp-content/upl...-2005-2009.pdf
Balmar Duo Charge for the start battery
Alternator: Paris-Rhone 50 Amp with 2" pulley (2:1 ratio)
Solar: Two panels in parallel, with regulator, for 40 watts max

Refrigeration: Converted ice box, about 6 ft-cu, with air cooled Danfoss BD35F compressor.
Reefer load about 40-60 amp hours per day.

I cruise every June for 4-5 weeks, single-handing, always anchoring, never shore power, no marinas except for wine, ice cream and water (haven't figgered out how to change water to wine yet). The rest of the summer is on a mooring with day sails several times a week.

The reefer load is by far the biggest boat amp-hour load, even in Maine with water temps rarely above 65°F, and the solar panels give back maybe 50% of that (if the sun's out). If the house bank is discharged 25% or so, the Balmar 612 charges at bulk (starting at 50 amps and quickly dropping off to 35 amps) for 30-45 minutes, then to acceptance for an hour or so before dropping to float. I've never had the 612 cut back field current due to high Paris-Rhone alternator temp (I had a 70 amp Balmar alternator whose case would go over 180°F and the 612 would cut output back as designed). Since we often have no wind here in the summer until about 10AM, I generally motor for an hour or so while transiting, and that recharges the batts.

In summary,
a) Get the Balmar regulator (it looks like the 612 has been superseded by the 614, generally a sign of a price hike) with alternator and/or battery temp sensor, it Works Fine, Lasts Long Time (old engineering maxim) and is fully adjustable.
b) I fully agree with Neil: get one or more solar panels and regulator. My 40 watts is too small, go for more.

[hanleyclifford]

Thanks for that, Tac - I especially like that small engine mode feature. The 614 seems to be able to deliver what I need (but my requirements are about double yours). Now to come up with the scratch...

[Ball Racing]

Nothing to do with the alternator

It would be better, and it is better; but if you follow the thrust of this thread you can feel the pain in your front crankshaft bearing and valve train when the thing kicks in. For engine health a way must be found to mitigate.

Wow, I let my boat warm-up about 5+ minutes then go put her up on plane.... With RWC I never warm-up above 100 unless under hard load..

[hanleyclifford]

Wow, I let my boat warm-up about 5+ minutes then go put her up on plane.... With RWC I never warm-up above 100 unless under hard load..

Aye, but what output do you demand from your alternator?

[sastanley]

Nothing to do with the alternator either!

Daniel, In the spring and fall, yes, it is hard to get the temp gauge off of the peg. And mine will run 140°F under light load (and clean bottom & prop )

[BadaBing]

The 1.75:1 stock ratio I mentioned came from A-4 specifications found here.

I'm sure you've analyzed your needs down to the gnat's hair but if I were planning prolonged cruising away from the dock with refrigeration I'd be looking at solar for sure, perhaps an engine driven refrigeration compressor with holding plates like the BVI charter fleet used successfully way back when I was there. Their charter instructions called for one hour of daily engine run time and they kept up (batteries and refrigeration) just fine without solar and if my memory hasn't failed completely, this was well before 3 stage smart chargers were popular.

About Tac's amperage comment, I didn't consider the amperage specification of the time delay relay I referenced so thank you. However, I could not help but think about the perceived concern of alternator loads during warm up and their significance. Has anyone ever had a problem? Is this an automatic charging relay concern? With my Jurassic manual battery switch system I start and warm up on an isolated starting battery, switch over to the house bank when I am ready.

I am still mystified by pv solar electric. Any advise on sources for hardware and tech..data?

[tac]

Alternator HP Load

On starting, my Balmar 612 regulator excites the field after 90 seconds, and ramps up the excitation to the maximum it calculates is needed over another 60 seconds. By the 90 second point, I have the choke off and throttle set at 1500RPM while the engine warms up. When the alternator has come up to a full 50 amp output, the engine RPM has dropped to 1200 RPM. How much horsepower is needed to run the alternator at 50 amps?

If the alternator is putting out 50 amps at 14.4VDC (a common bulk mode voltage for AGM batteries), then the output power is:

P = IxV = 50A x 14.4V = 720 watts

But wait! There's more! The alternator is putting out lots of heat. These loses are due to stator and rotor winding resistance, bearing friction, magnetic field loses (Eddy current loses), rotor windage, flexing of the alternator belt and bracket, and maybe moon phase. For the small case alternators most of us have, these loses result in about 50% efficiency (small case alternators are limited by their size in the amount of iron in the frame - less iron, lower efficiency). Assuming a 50% efficiency to make 720W of electrical power, the heat produced would be another 720W. That means the engine would have to produce:

P = 720 + 720 = 1440 Watts.

We want to know the horsepower required to make 720 watts of heat and 720 watts of power. The basic conversion is 1 horsepower = 746 watts. So the engine horsepower required is:

P = 1440/746 = 1.9HP

The Atomic4 horsepower curve from Universal shows the engine output at 1500RPM to be 11.7HP, and about 9HP at 1200 RPM. This would indicate it takes 2.7HP to run the alternator at 50 amps. Keep in mind though, that Universal's data was most likely made on a dynamometer (brake), with the engine at full throttle for each measurement. At part throttle the actual horsepower at each RPM would be lower. So:

Theory: 1.9HP
Actual: < 2.7HP