Solar powered 12 volt fan.

[youboom]

I wish to generate air flow through my boat on still,cold, clear days. (ie days when there often is early morning fog)
On these days I often get heavy condensation on the deck head as the cold damp air in the bilge heats, rises and condenses.
My solution is to hang a large slow fan in the, companion way and power it by a solar panel.I want this totally independant of the batteries.
I have located a suitable fan and solar panel. The problem is regulating the voltage to remain within the limits of the fan.
I don't need the fan operational other than on days of bright sunshine.
Is there an of the shelf voltage regulator that would do the trick?

 

[VicS]

I wish to generate air flow through my boat on still,cold, clear days. (ie days when there often is early morning fog)
On these days I often get heavy condensation on the deck head as the cold damp air in the bilge heats, rises and condenses.
My solution is to hang a large slow fan in the, companion way and power it by a solar panel.I want this totally independant of the batteries.
I have located a suitable fan and solar panel. The problem is regulating the voltage to remain within the limits of the fan.
I don't need the fan operational other than on days of bright sunshine.
Is there an of the shelf voltage regulator that would do the trick?

I dont think any of the solar panel battery charging controllers will be suitable.

The simple ones just disconnect the panel when the battery volts rises to some predetermined figure

PWM ones control by breaking the charge into a series of pulses of deceresing length as the battery volts rise.

MPPT ones are aimed at maximizing the solar panel output.

Maybe some form of zenner diode controlled voltage stabilization circuit ?

 

[Rivers & creeks]

How about a small battery, let the solar panel charge it and fit a cut off to the fan if the voltage drops below 12.4v. The battery needn't be bigger than say 20ah.

 

[rich]

I just leave my solar panel connected strait to the fan, you can here the fan going up & down when it clouds over.

 

[sam_uk]

lm2596

I'd have a look for something like this:
http://www.prodctodc.com/lm2596-dc-...wer-supply-buck-module-p-70.html#.UVNwbvFSzWl

There is a supplier of the waterproof ones somewhere in the UK but I can't find it off hand.

Good luck

Sam

 

[Rigger Mortice]

What are the power ratings of the panel and fan? If the panel isn't too big a direct connection will be fine.

If you do need a regulator there are plenty of off the shelf devices available on Ebay. What you need would depend on how much power it needs to handle.

 

[William_H]

As said it a matter of matching the fan to the panel. More often too high a powered panel will over power a small fan. hence it is far easier to connect the panel to the ships battery and run the fan off the battery.
If you don't want to do that then a small regulator chip generically called a 7812 will regulate to 12v regardless of input voltage up to 30v with a current rating of 1 amp derated with higher input voltages. However to get 12v out it needs more than 15v in which is probably Ok for your solar panel but not for a smaller panel near the power rating of the fan. (in which case connect directly anyway). Just google 7812 or voltage regulators for wiring diagram.
There are small switch mode regulator boards available from China which will give 12v over a wide input voltage range ie from 5 to 30v.
A variable or fixed series resistor might be satisfactory to limit power to the fan. You probably need to drop 5v at a guess .1 amp R=E/I so 50 ohms might be a good start for a fixed resistor. Just measure the voltage on the fan when it is running try to get it close to 12v. Maybe more if you are willing to shorten life of fan. a lower voltage will dramatically reduce air movement from fan.

 

[lenseman]

I wish to generate air flow through my boat on still,cold, clear days. (ie days when there often is early morning fog)
On these days I often get heavy condensation on the deck head as the cold damp air in the bilge heats, rises and condenses.
My solution is to hang a large slow fan in the, companion way and power it by a solar panel.I want this totally independant of the batteries.
. . . . . .

I am not so sure that you will find the fan idea much good.

The problem sounds like a "dew-point" problem but then you also state that it happens on days when there is early morning fog? This is a problem as the air (that you intend to move) will already be saturated and might not be able to absorb any more water from the deck head once the fan stirs the air inside your boat.

It sounds like the deck head is a painted surface or a plastic or even metal surface and changing this might be a better way forward?

In the Royal Navy they used to paint deck heads with "Korkon" paint which is a paint with small cork particles suin it and these stop the cold penetrating through the pain and therefore the water vapour does not condense on the surface. This might be a better way forward. I have known people fitting hiking sleeping mats to deck heads to counter any condensation problems, this might also be a way forward for you?




.

 

[lenseman]

Google "Anti-condensation paint" - you might find something useful in NZ?



.

 

[Alex_Blackwood]

A 12 volt Dehumidifier may be a better bet.

 

[MYStargazer]

How about one of these? http://www.solarshop.co.uk/solar-powered-ventilation/solarvent-svt224s-battery.html

 

[youboom]

How about one of these? http://www.solarshop.co.uk/solar-powered-ventilation/solarvent-svt224s-battery.html

I had these but the power supply lasted only a few years. They leak with green water over them.

 

[youboom]

What are the power ratings of the panel and fan? If the panel isn't too big a direct connection will be fine.

If you do need a regulator there are plenty of off the shelf devices available on Ebay. What you need would depend on how much power it needs to handle.

The fan needs 10.5 V to 13.5v. I have enquired what happens out side this range. The panel is 5 watts but as yet I don"t know how clean the voltage is.

 

[youboom]

I am not so sure that you will find the fan idea much good.

The problem sounds like a "dew-point" problem but then you also state that it happens on days when there is early morning fog? This is a problem as the air (that you intend to move) will already be saturated and might not be able to absorb any more water from the deck head once the fan stirs the air inside your boat.

It sounds like the deck head is a painted surface or a plastic or even metal surface and changing this might be a better way forward?

In the Royal Navy they used to paint deck heads with "Korkon" paint which is a paint with small cork particles suin it and these stop the cold penetrating through the pain and therefore the water vapour does not condense on the surface. This might be a better way forward. I have known people fitting hiking sleeping mats to deck heads to counter any condensation problems, this might also be a way forward for you?




.

You are correct. the problem only occurs on dry cold days after the sun comes out and heats the cold damp air lying low in the boat.
The idea is that the sun would power the relatively large 300mm. dia. slow revving fan and suck this air out of the boat, before it condenses on the deckhead.
If I am on the boat on these occasions and open the forward hatch the air flow dries the boat very quickly, which is why I believe the fan idea will work.

 

[Rigger Mortice]

The fan needs 10.5 V to 13.5v. I have enquired what happens out side this range. The panel is 5 watts but as yet I don"t know how clean the voltage is.

We need to know current the fan draws. The voltage is only part of the equation.

From what you say you are trying to do I'm not sure why, if you can do it securely, you don't just leave the hatch open a fraction. Natural ventilation will usually be better than a fan.

 

[charles_reed]

I am not so sure that you will find the fan idea much good.

The problem sounds like a "dew-point" problem but then you also state that it happens on days when there is early morning fog? This is a problem as the air (that you intend to move) will already be saturated and might not be able to absorb any more water from the deck head once the fan stirs the air inside your boat.

It sounds like the deck head is a painted surface or a plastic or even metal surface and changing this might be a better way forward?

In the Royal Navy they used to paint deck heads with "Korkon" paint which is a paint with small cork particles suin it and these stop the cold penetrating through the pain and therefore the water vapour does not condense on the surface. This might be a better way forward. I have known people fitting hiking sleeping mats to deck heads to counter any condensation problems, this might also be a way forward for you?




.

Right on. I've found additional insulation as a much more effective way forward than any increase in ventilation - anti-condensation paint just stops big drips forming. But that's why one used to get "hard-lying money".

The cheapest way is to use polystyrene backed aluminium foil sandwiched behind 4mm marine ply. The polystyrene/foil was sold for insulation behind central-heating radiators by most of the big DIY chains. I first used it in lockers when ambient outside was -8c and I'd a nice 20C fug inside - immediate cure, so extended to the rest of the deckheads.

 

[youboom]

We need to know current the fan draws. The voltage is only part of the equation.

From what you say you are trying to do I'm not sure why, if you can do it securely, you don't just leave the hatch open a fraction. Natural ventilation will usually be better than a fan.

You need some wind for teh natural ventilation, my problem occurs after the sun comes up but before the wind.

The fan draws 3amps.

 

[Rigger Mortice]

The fan draws 3amps.

Sorry to say so, but what you've got is going to be dissappointing.
The fan draws 3amps, so it needs 36 watts to power it (3 amps x 12 volts)
Your panel is 5 watts so, at best, it will turn the fan over very gently.

You need a much bigger panel or a rethink. Sorry.

You might get it to work by using the panel to charge a small battery during the day. You would then use the battery to power the fan for tweny minutes or so in the morning.

 

[youboom]

Sorry to say so, but what you've got is going to be dissappointing.
The fan draws 3amps, so it needs 36 watts to power it (3 amps x 12 volts)
Your panel is 5 watts so, at best, it will turn the fan over very gently.

You need a much bigger panel or a rethink. Sorry.

You might get it to work by using the panel to charge a small battery during the day. You would then use the battery to power the fan for tweny minutes or so in the morning.

Thanks for the info.i will look for a more efficient fan.

,

 

[Rigger Mortice]

Thanks for the info.i will look for a more efficient fan.

To be honest I think you're on a hiding to nothing with the panel you've got unless you use a battery. If you really do want to drive a fan direct from the panel you will need a small fan...the kind of thing which is used to cool computers. Those fans will push air around a few components in a computer but they will have little effect inside a boat which is much larger.

Anyhow, that's my view. Sorry. Good luck whatever you decide to do.