how to keep the batteries charged

[fredrosse]

Looking up tech data for a marine 12 Volt alternator (Balmar 6 Series, with internal voltage regulation built-in, the smallest of their marine line) gives the following data:
Rated output: 70 Amps at 14.1 Volts.
Operating speed range: 1,320 - 15,000 RPM
About 2000 RPM is needed to get the alternator into reasonable efficiency, with an output of 50 - 60 Amps.
50 Amps x 14 Volts = 700 Watts Output
Alternator Efficiency is in the general vicinity of 50 % - 60%, based on what I could find for similar machines, although the Balmar datasheet does not specify this number.
700 Watts Output at 60% efficiency = 1167 Watts Shaft power Input = 1.56 Horsepower Alternator Shaft Input Required. To that one must consider the efficiency of the drive system from the Engine to the Alternator Shaft, probably 90% or better with a proper serpentine belt drive, and a ratio of 8:1 or similar, then engine horsepower required is 1.75 Horsepower, a healthy number for our small launch engines.

The smallest automotive alternators I have seen put out 30 Amps, these would require about half the input engine power, and would probably require a somewhat higher running speed.

[barts]

A small solar cell panel can also be used for boats that spend much time away from shore power; this is simple and easy to rig. We use this on our Airstream travel trailer. Another approach is to drive a small DC motor via a belt and to use the proper electronics (dc-dc converter) to provide regulated 13.6 V for battery charging... this is more efficient than an alternator, but of course delivers far less power.

Our Otter uses a 12V 85 AH gel cell for running lights and an electric fuel pump; this has never run short of juice, even on long vacations w/o a charge.

- Bart

[dhic001]

Thanks to those who posted thoughts on this, and thanks to Den for the picture. in the future (when money allows) I will investigate this further on Zeltic. While a battery charged off shore power has worked ok in the past, I intend to fit more electrical devices in the future (GPS Chartplotter/Depthsounder, spotlight, proper lighting throughout the boat, VHF, autopilot and the ability to take a fridge unit away), so will need charging ability at night. When I make some progress, i'll post it on here.
Daniel

[RogerV]

As a total newcomer here, I'm a little hesitant to jump in, but in my searches on the web I came across motorcycle electrics. I also discovered that they still make generators for use on Harleys. Not knowing much about it, I assume that Harleys operate at lower RPM's than do modern motorcycles. I also don't know much about output, but perhaps someone else in this forum can comment and/or tell me if I'm onto something or just on a wild goose chase.

BTW, I have a brother on the East Coast who owns a beautiful 41-foot sailboat. In one of my conversations with him, he couldn't fathom why someone would be interested in something as "complicated" as a steamboat. I say that someone who has to deal with sails, rigging, masts, a diesel engine, a diesel generator. a heat pump, and the need to constantly adjust sails every five minutes has no business calling a steamboat complicated!

[mtnman]

I also discovered that they still make generators for use on Harleys. Not knowing much about it, I assume that Harleys operate at lower RPM's than do modern motorcycles. I also don't know much about output, but perhaps someone else in this forum can comment and/or tell me if I'm onto something or just on a wild goose chase.

First I've built and ridden Harley's for almost forty years and I've had Flatheads, knuckleheads, Panheads, Shovelheads and an Evo. In my opinion the weak part of a Harley is the generator. They've never been reliable and when they do work they are not really sufficient to run more than a couple of lights. All the Harley Engines prior to the Shovelhead with an alternator could be equipped with a magneto ignition (good insurance that you won't be walking).

[Rainer]

I am also have not found the best solution for the electric power supply on my steam boat - here are my thoughts on this:

The car type generators need high rpm - you can archive this with a belt but with this you have the bad sound of high rpm spinning parts...

Additional the efficiency of this generators is designed for much higher output as needed on a steam boat.

On Emma I only operate the lights. With todays LED technologie I can do this with 10x 1.2Volt 2500 mAh AA rechargable Batteries for the time to come home at night. While I am not using the boat (most time of the year) I can use the AA cells in other electric equipment. If I am running low on electricity I even could buy some Batteries in every shop or gas station - this keeps my steam boat simple!!

Additional I focused on using a DC motor to generate power for a cell phone or the GPS on longer trips. Most of this systems are using 5 Volt. So you don't need the 12 Volt car batteries. If you generate the electricity constantly, maybe you can use a bicycle hub generator. It operates on low rpm with 6 Volt and 3 Watt - should be enough for a GPS and a MP3 player...

For higher output you can use every brushed DC motor from Ebay. I bought some Ametek 38 Volt / 10 A / 2000 rpm motors for my CNC mill and found out that they have a good output at low rpm. You only have to build a DC/DC system to stabilize the voltage - or regulate the charging process by hand like your boiler )

Unfotunately the Ametek motors becoming more and more expensive because they ae out of production and well known for CNC milling and wind turbine projects. I bought mine for 30 US$. Today you have to pay 100 US$ and more on ebay...

If you are looking to concvert a DC motor to a generator it should have a big diameter and lots of poles and a high rated Voltage on low rpm. Today you will find this for the electric scooters on ebay. Don't know about the power output of this motors on low rpm

[johnp]

I'm building my first steam boat, I plan on mounting a large solar panel within the wood frame of the canopy facing up of course, all lights will be led and I will add a stereo and electric bilge pump. I think 2 or 3 batteries will keep it working it will be charging while crazing and when sitting at the dock.

[DetroiTug]

There have been a few posts on this subject in the last few weeks; mine and others.

I will put the info together on the results of the tests I've ran. The alternator was not suited for the task: requires too much RPM and not very efficient at low RPM's. I've now went to a Nema 23, 60 volt DC servo and it appears to work very well at the 1000 - 1500 shaft RPM. 7 amps continuous at 1200 RPM. Using a bridge rectifier (the diodes from it) to keep the current going in one direction. I think it's going to work very well. Cheap to put together too. Under a hundred for all new parts.

Probably only using about 1/20th of a horsepower. I was holding it with one hand when it was putting out 7 amps, not much torque at all.

In my searching I came across a nice little PMA alternator that Kubota put on their Lawn tractors. It was $107, fearing taking on another I/C device that is unsuitable, I abstained.

http://www.ebay.com/itm/NEW-Permanent-M ... 53e9f28d15

Would work with a standard full wave bridge I would think.



-Ron

[Dhutch]

Had a squint at the artical in the current funnel on the same topic last night.

After a few iterations Emilyanne now uses a large coach alternator modified from delta to star topology and powered from the propshaft/engine via a 6:1 ratio belt (inch pulley down to a 3inch, using a pair of t-link splitable belts) which generates around 30amps at 24vdc from a engine speed of around 150 rpm onwards. Obvisously being a narrowboat both our engine and electrical demands are larger but while you can tell when the fridge cuts in by the slight decrease in revs the setup now works and reliably well.

Several of the other narrowboat have a small dedicated 'generating engine' taypically a 5A which is another way of doing it, and i guess one option for a launch, depending on demand, would be to incorporate a clutch to disengauge the prop and allow the main enigne to be used for generation in the evening.

Else obviously for light load over a weekend, some well charged lead acids could simply be maintained when mains was available.


Daniel