Alternator Curves

[Ball Racing]

Originally Posted by hanleyclifford

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]

Originally Posted by Ball Racing

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]

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]

Originally Posted by ndutton

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]

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

[edwardc]

Originally Posted by ndutton

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,...

Originally Posted by tac

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.

...
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.

Neil,
Thanks for the reference on the 1.75:1 ratio.

And yes, I have more. The boat came with a 400 Watt AirX wind generator, which has been pretty useless in the Chesapeake, but should do fine in the Bahamas. In addition, I am also in the process of adding two 100W polycrystaline solar panels and an MPPT solar controller. I figure sun or storm, I should be making some juice! And my refrigeration unit is a 12v cold plate system.


Tac,

Your system sounds very close to mine, right down to the U1 for a starter battery (although all my batts are gel cells), and the converted icebox. And the Balmar 614 is one of the regulators I'm considering.

[ndutton]

Not trying to change anybody's mind, my boat is electricity dependent too but if I were setting up a boat for cruising - not local stuff but months away from the dock - I'd be doing as much as I could without electricity:

• Refrigeration would be with an engine driven compressor and holding plates, box insulation would be beefed up.
• Cooking would be done on a stove/oven or BBQ. No microwave, no toaster oven, no George Foreman grill.
• Pressure water would be gravity fed from a modest day tank mounted at deck level. There would be a high volume hand pump to fill the day tank from the main tanks daily.
• All lighting would be LED, no question, 1/10th the load compared to incandescent or halogen.
• Anchor light would be kerosene.

With these measures and anything else I could think of there would be little demand on my electric system and therefore little demand on a charging system to feed the beast. As mentioned earlier in the BVI charter fleet observation, daily engine run time would meet the demands of the refrigeration, simultaneous battery charging would be a side benefit. Solar would be a bonus and could be more modest in size and expense due to lessened demand.

[tac]

If anyone is looking for a timer/time delay relay, try this.

http://www.amazon.com/Timer-Delay-Re...productDetails.

It claims to have a 5A output. I just got one, and set it up as a flasher with one incandescent bulb. Works good. When set up as a time delay, and as a one-shot, it also does fine. Cheap too.

I haven't tested it yet for the 5A out, but judging by its size (5/8" x 3/4" x 3/16") and lack of heatsink, it's hard to believe it will put out 5A for long. It should be able to drive an ice cube relay though. You can download the pdf manual at:

www.bit.ly/timer17

[hanleyclifford]

I believe the field could need as much as 10 amps.