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Windhunter · 29-11-2015, 19:21

Want to re power a 30 to 42 ft sailboat.
Purchased a CE-NIEHOFF 400amp dc alternater daul charging 14 &24vlt . Would it be possible to power a 25 hp to 30 hp dc motor with the same concept as a automobile? Doing a little research not sure of the numbers. I belive a 25hp would require some were in the range if a 175 amps full load. That would leave around 200 amps give or take a certain % of loss in the system. Would this alternater under load of motor and charging duty of a say 4 × 200 ah put out the required amperage to give me unlimited motoring capacity if the system was kept within safe operating temperature by possible fan cooling.
Fair Winds
Windhunter

**StuM** · 30-11-2015, 01:49

Not quite sure what you are asking.
What is the power source driving the 400 Amp alternator?
Is that 400 Amps @ 12 or 24 V?

Regardless, something is way out with your calculations. I don't know how you come up with 25 HP = 175 Amps (voltage unspecified).

Doing approximate raw conversions without any efficiency losses, your 400 Amp alternator will output:
400 Amps @ 12V = 4.8kW = 6.5 HP, at 24V = 13 HP

Going the other way. Requirement to drive 25HP at "full load":
25 HP = 18.6 kW = 1550 Amps @ 12V, at 24V = 775 Amps.

Windhunter · 30-11-2015, 09:05

Quote:

Originally Posted by StuM

Not quite sure what you are asking.
What is the power source driving the 400 Amp alternator?
Is that 400 Amps @ 12 or 24 V?

Regardless, something is way out with your calculations. I don't know how you come up with 25 HP = 175 Amps (voltage unspecified).

Doing approximate raw conversions without any efficiency losses, your 400 Amp alternator will output:
400 Amps @ 12V = 4.8kW = 6.5 HP, at 24V = 13 HP

Going the other way. Requirement to drive 25HP at "full load":
25 HP = 18.6 kW = 1550 Amps @ 12V, at 24V = 775 Amps.

Hi StuM
The alternater I have puts out 14/28 vlt @400 amps.what I'm trying to do is start a 25 hp dc motor off a batt bank,the alternater will be connected in the system via a v belt . If your numbers are correct and it takes 775 amps to power a 25 hp motor at 24 vlt, if I have 975 amps available (another 575 amp @24vlt ) when the EP is engage and EP will be powering the alternater's and the vessel is the plan. Is this doable .
Windhunter

**StuM** · 30-11-2015, 14:07

Oh, I see. Another perpetual motion machine.
The alternators power the engines which power the alternators.

Doesn't work like that. Alternators are not "free energy". They need HP from the engine to generate the Amps.

To get your 975 Amps @ 24V, if your alternators are 80% efficient, they will need almost 40 HP of engine power to drive them before you put any power into actually moving the boat. That 40 HP obviously can't come from the 25 HP engine that the alternators are driving.

Windhunter · 30-11-2015, 16:06

Hi StuM
Thanks for the input,I realize that perpetual motion is a possibility in the future . I was hoping with a Lifepod batt bank of say a 1000ah's I could I could make this a possibility. I guess I will have to incorporate I guess a small generator into the system and operating on the brown gas it may be more feasible?
Fair Winds
Windhunter

Windhunter · 30-11-2015, 22:01

Gentleman
I'm not sure what your implying but my question was sincere. If It was the the brown gas I meant hydrogen gas from an electrolyzer. I can assure you I'm far from a troll. But whatever I hope the rest of the community is a bit more friendly. No harm
The best to you both.
Fair winds
Windhunter

Windhunter · 01-12-2015, 00:48

Apparently I went about this the wrong way. So let's try this again. I'm not an engineer, but I'm creative,
Would like to re power my Hunter30 with EP.
I have purchased an dual voltage 12vlt, 24vlt 400amp CE-NIEHOFF alt, and thanks to StuM I'm now aware it will take 775 amps to power a 25hp/24vlt at full load. Would a lithium iron battery bank of 1000 ah and a 4 kw gen. Give my vessel long range motoring capacity?say 200 nm or more. Any suggestions on a motor/controller maufacture as I would prefer to create my own EP.
Fair Winds
Windhunter

LakeSuperior · 01-12-2015, 01:38

Quote:

Originally Posted by Windhunter

Apparently I went about this the wrong way. So let's try this again. I'm not an engineer, but I'm creative,
Would like to re power my Hunter30 with EP.
I have purchased an dual voltage 12vlt, 24vlt 400amp CE-NIEHOFF alt, and thanks to StuM I'm now aware it will take 775 amps to power a 25hp/24vlt at full load. Would a lithium iron battery bank of 1000 ah and a 4 kw gen. Give my vessel long range motoring capacity?say 200 nm or more. Any suggestions on a motor/controller maufacture as I would prefer to create my own EP.
Fair Winds
Windhunter

The simple answer is yes it would. You would have long range motoring capacity.

Only you would not have 25 hp available. Since you would not want to run the generator at rated maximum output continuously you would maybe run it at 3 kw output. You will get about 1.34 hp for every kilowatt so you would have about 4 hp to play with.

The engineering principle underlying your questions is known as the principle of "no free lunch." Energy is conserved.

IMHO you risk spending a lot of time, sweat, and money working on a Rube Goldberg contraption that ultimately will not work as desired because you simply do not have the engineering skills and experience to design a practical reliable system. There is a substantial body of knowledge you are not only missing but seem to be unaware of.

This is not a bad thing as each individual cannot know everything about everything. That said I actually have some friends that think they know everything.

You could spend some quality time learning what you need to know or you could buy an off the shelf unit where years of engineering and trial and error have already been invested.

With all due respect to your creativity, I believe that engineers and scientists are the most creative people on the planet. Just look around you. Artists are still singing the same songs and painting the same flowers.

In conclusion, I will take a stand here and say you are wasting your time on this endeavor. Your creativity will not stand in this project.

**StuM** · 01-12-2015, 02:04

Assuming you batteries are 1000 Ah @ 24 V in the best case. That is 24kWh of which maybe 20kWh are useable. 20kWh = about 26HP hrs.

On those figures, your battery bank is good for just over 1 hr of running a 25HP full out or 3 hours @ 1/3 power. Let's be generous and assume that your Hunter 30 in calm conditions can do about 5 knots on 8-9 HP (or about 6-7kW). That gives you a range of 15 miles on a full battery charge.

But let's also assume that you are running your generator non stop. That means that your generator is providing 4kW and your batteries need to provide another 2kW. It can do that for 10 hours before you have used the 20kWh available from the batteries. So you are looking at a range of about 50 nautical miles if running your generator before you run out of battery power. That 50 nautical miles is effectively your "motoring capacity". Nowhere near your desired 200.

At the end of that 10 hours, you need to replenish the batteries so have to stop motoring and direct all of the 4kW to your batteries for at least 5 hours.

...rinse and repeat...

Bottom line. If you run your genset 24/7 you could average 80 Nm per day with 5 hour stops after every 10 hours running.

This of course assures no efficiency losses and no other electrical draws such as lights, instruments etc.

In reality, you would be lucky to get 2/3 of the above mileages.

Added: the obvious point is if you are going to be running a genset 24/7, why not use the fuel to directly drive a diesel engine without all the inefficiencies involved in convertions of energy from one form to another.

**Dockhead** · 01-12-2015, 03:17

Quote:

Originally Posted by Windhunter

Gentleman
I'm not sure what your implying but my question was sincere. If It was the the brown gas I meant hydrogen gas from an electrolyzer. I can assure you I'm far from a troll. But whatever I hope the rest of the community is a bit more friendly. No harm
The best to you both.
Fair winds
Windhunter

In all of these conversions from one form of energy to another -- electrical power to hydrogen, hydrogen to electrical power, mechanical energy to electrical power --

The energy you get will be less than what goes in. Mankind does not know a single process which produces more power than what goes into it. So the electrical energy required to produce hydrogen gas by electrolysis is considerably more than the electrical energy you get back out by burning (or converting in a fuel cell) the hydrogen gas.

So you should forget about trying to get energy for nothing. Mankind does not yet know any way.

To get 25 horsepower worth of electric propulsion, you will need to be producing the electrical power using considerably more than 25 horsepower of diesel power. You can improve the efficiency by sizing the generator to average, rather than peak loads, and using a battery bank to shave the peaks. But a "small generator" might not be enough -- it will need to produce enough power to replace the energy used plus all the conversion losses over whatever maximum period your batteries can "lend" you your short-term needs. There is no free lunch!

This is hybrid propulsion and requires a lot of serious engineering work to do it well. If you want to tinker for its own sake, then go ahead -- I can see how that could be fun. But if your main purpose is the result, then you would be better off with a solution already developed by engineers with a serious R&D budget.

**Dockhead** · 01-12-2015, 03:30

Quote:

Originally Posted by StuM

Assuming you batteries are 1000 Ah @ 24 V in the best case. That is 24kWh of which maybe 20kWh are useable. 20kWh = about 26HP hrs.

On those figures, your battery bank is good for just over 1 hr of running a 25HP full out or 3 hours @ 1/3 power. Let's be generous and assume that your Hunter 30 in calm conditions can do about 5 knots on 8-9 HP (or about 6-7kW). That gives you a range of 15 miles on a full battery charge.

But let's also assume that you are running your generator non stop. That means that your generator is providing 4kW and your batteries need to provide another 2kW. It can do that for 10 hours before you have used the 20kWh available from the batteries. So you are looking at a range of about 50 nautical miles if running your generator before you run out of battery power. That 50 nautical miles is effectively your "motoring capacity". Nowhere near your desired 200.

At the end of that 10 hours, you need to replenish the batteries so have to stop motoring and direct all of the 4kW to your batteries for at least 5 hours.

...rinse and repeat...

Bottom line. If you run your genset 24/7 you could average 80 Nm per day with 5 hour stops after every 10 hours running.

This of course assures no efficiency losses and no other electrical draws such as lights, instruments etc.

In reality, you would be lucky to get 2/3 of the above mileages.

Added: the obvious point is if you are going to be running a genset 24/7, why not use the fuel to directly drive a diesel engine without all the inefficiencies involved in convertions of energy from one form to another.

The case you describe is the illustration of an undersized generator. Get the generator sized for the average load and you have unlimited range (subject to fuel capacity).

Hybrid propulsion has some serious advantages over simple mechanical propulsion. Besides peak-shaving (which allows you to size the engine better), and operating the diesel engine always near its maximum efficient load, you also have some advantages in propeller design because of the nature of how electric motors work (maximum torque at 0 RPM).

But hybrid propulsion is costly to engineer right and build. At present there's no way that the efficiency gains will pay for the capital cost in savings on fuel, for pleasure boats of moderate size. Maybe get closer when a well developed, mass produced hybrid system comes to the market.

Diesel engines are not that inefficient at partial load. That's because they don't have pumping losses from a throttle plate, like gasoline/petrol/spark ignition engines do.

So having a diesel main propulsion engine sized for the rare peak load, and mostly used at 20% or 30% of its capacity is not actually all that inefficient.

So our normal, standard, direct drive diesel propulsion system is really pretty good, particularly what concerns bang for the buck.