Converting pontoon boat to full solar power.

[Solarcraft]

Hello everyone.

I have a project on the go and I would like to get some advice on what would be the best options to rig up solar panels on an aluminum pontoon boat.

One of the pontoon boats I am planning to convert is 19 feet by 8 feet / 5.8 by 2.4 meters.
I plan to cover the entire boat with panels, so I can do 9 X 360 watt panels... the panels I can get are 3.3 X 6.6 feet or 1 X 2 meters.
( Being in Thailand, sunlight is almost always there and shade is a good thing!)

Anyway I figure the total watts will be around 3200 watts.

I was thinking about get several small charge controllers and using only 1 or 2 batteries as a buffer but running mainly on the power from the panels

... Lately I have been thinking about using dc to dc buck converters.
I am thinking ,, If I was to get a buck converter for each panel and connect them in parallel, I would need an automatic cut in and off switch to protect the battery right!??
My inverter is 6000 watts 12 volts pure sine wave so I want to stay with 12 volts.
I know I can run an AC motor from there which will be cheap for me to get.

If anyone out there can tell me if I am mistaking about using buck converters? And about the battery protect switch does anyone know what I could use??
Alex.

 

[FilterGuy]

We need to know more about your system.

1) is the planed motor AC? What voltage? What is the run-time current?
2) Are you planning on running other things besides the motor.
3) Why are you thinking of using buck converters?

If you could provide some type of drawing of the planned system it would be helpful.

 

[Solarcraft]

We need to know more about your system.

1) is the planed motor AC? What voltage? What is the run-time current?
2) Are you planning on running other things besides the motor.
3) Why are you thinking of using buck converters?

If you could provide some type of drawing of the planned system it would be helpful.

Yes I plan to use a 220 volt AC motor because it's easy to get in Thailand and I already have the inverter.

I plan to match the motor power to the output of my solar array ... So I'm thinking 1500 to 2500 watt motor and maybe use a dimmer switch to tune the power to what I get from the panels.
( I am not looking to make speed, I know I will be limited to what I get from the panels for now)
If that answers the run-time current question...

No, not planning to run much else other than the motor for now.

I was thinking using buck converters because it might be a cheaper way to go since I plan to only use 1 or 2 batteries in the beginning
but that's just an idea..

I'll try to draw a little diagram if I can..

 

[Solarcraft]

We need to know more about your system.

1) is the planed motor AC? What voltage? What is the run-time current?
2) Are you planning on running other things besides the motor.
3) Why are you thinking of using buck converters?

If you could provide some type of drawing of the planned system it would be helpful.

 

[FilterGuy]

ok.... I think I see what you are trying to do. However, I would not recommend using a buck converter as a charger. If you do, make sure you store the boat in the shade or disconnect the converters from the battery when not in use. Otherwise, you run the real risk of over-charging the battery.

I would at least use a decent PWM charge controller. These can be relatively low cost and still keep the batteries safe. (With PWM, you want to try to match your panel voltage to the battery voltage (Use 12v panels) in or to maximize your solar generation.)

Since you are looking at an AC motor, you will probably find that a dimmer will not be very good at controlling the speed. (you probably could not find one that can handle that wattage anyway.)

There are 3 or 4 ways to control ac motor speed.

Multiple winding taps from the motor. Some AC motors have multiple leads that can be powered for different speeds. This is probably not going to be the type of motor you end up with.

Variable voltage: (This is how the 'dimmer' idea would work if you found a dimmer large enough. With this you plan on the motor 'slipping' a lot and you might find the control is not very accurate. Furthermore, you could burn out your motor if you are not carefull. (The low cost motor you inferred would probably not hold up very well. The voltage can be controlled several different ways ranging from a very large variable resister to a variable voltage transformer. In general, variable voltage on an AC motor is going to be *Very* inefficent.

VFD (Variable Frequency Drive): This is a device that takes your 60Hz AC in and outputs a variable frequency out. To adjust the speed of the motor you adjust the frequency out. This method gives both effecentcy and good speed control.