Boat friendly Solar Controller

[Ian Mac]

Right folks here is the challenge. I am struggling to find a negative earth, solar panel controller 20A or more preferably one which is PWM, however the important thing is when the batteries become fully charged I want the solar current to switch over to another load, a set of fans to purge the cabin air, some people may use this feature to charge a second set of batteries. I will put up with a +ve earth MPPT system as long as it has a battery full switch over mechanism. I have hunted high and low, but not found such a devise yet. I am considering using a standard MPPT controller and using the fully charged led to activate a relay to do the job, but the last one I bought didn't really cut the mustard as it lied about what was fully charged, an when t wasn't.

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cheers Ian Mac

Edited August 22, 2014 by Ian Mac

[b0atman]

It would make the boat cold in winter extracting all the heat .

I used to have a solar regulator that had connections for lights but never understood the thinking i.e. lights are what you use at night when the sun has set.

[Alan Saunders]

It would make the boat cold in winter extracting all the heat .

I used to have a solar regulator that had connections for lights but never understood the thinking i.e. lights are what you use at night when the sun has set.

I assumed that the lights were activated by the controller when the ambient light fell below a certain level? OTOH, I can imagine that an output active during daylight could be useful.

 

I think the OP, Ian Mac, needs to better define his problem rather than request a device that satisfies his solution.

Reading between the lines I think Ian wants to cool his boat with fans in hot weather but prioritise fully charged batteries.

 

If I were concerned by high internal boat temperatures I would run the fans from a thermostat and not worry about the SOC of the batteries. In the unusually sunny/Mediteranean air that we recently enjoyed the batteries would soon be recharged. Even now, with cold arctic air reducing day and night air temperatures, there is plentiful sunlight to recharge batteries. PV panels need radiation, not high air temperatures.

 

Alan

[Paul C]

Could be easily done using a battery monitor such as BMV or Smartgauge and one of its "alarm" functions custom set to SoC, switching a relay of items on or off. Then this feature would work with solar, alternator, mains battery chargers etc. Solar controllers never seem to also combine anything but very basic battery monitoring capability.

[Justme]

Outback FM 60 or 80.

 

Not the cheapest way to do it.

 

Doing it your way you are disconnecting the bats from the controller.

 

Thats not a good idea for the controller.

 

You would be better looking at load diversion whilst keeping the bats connected.

Edited August 23, 2014 by Justme

[Timleech]

I assumed that the lights were activated by the controller when the ambient light fell below a certain level? OTOH, I can imagine that an output active during daylight could be useful.

 

I think the OP, Ian Mac, needs to better define his problem rather than request a device that satisfies his solution.

Reading between the lines I think Ian wants to cool his boat with fans in hot weather but prioritise fully charged batteries.

 

If I were concerned by high internal boat temperatures I would run the fans from a thermostat and not worry about the SOC of the batteries. In the unusually sunny/Mediteranean air that we recently enjoyed the batteries would soon be recharged. Even now, with cold arctic air reducing day and night air temperatures, there is plentiful sunlight to recharge batteries. PV panels need radiation, not high air temperatures.

 

Alan

 

Probably more to do with ventilating a wooden boat, to reduce risks of decay, in Ian's case?

 

Tim

[John V]

Outback FM 60 or 80.

 

Not the cheapest way to do it.

 

Doing it your way you are disconnecting the bats from the controller.

 

Thats not a good idea for the controller.

 

You would be better looking at load diversion whilst keeping the bats connected.

 

Why is that? (serious question)

[Justme]

The battery sets the system voltage (like when setting the system up its connect the bat first then connect the array). So it could set itself to a higher voltage if its a multi voltage unit as most tend to be.

 

Or as there is no load the array voltage could peak. Not a problem is a properly speced system but if your cutting it fine with the running voltage & the controllers max voltage you could kill it.

[Ian Mac]

The problems As you will be able to tell from my profile I am one of the (co) owners of the NB Spey, The last original Clayton Motorboat, (all the other are total rebuilds and have lost important features such as the water tight stanks etc.). You will know that all Clayton boats where wooden, as Spey is. Being wooden she leaks and the bilges are wet and we have a couple of small pumps which keep on top of this. You can't get the oakum you know - a different problem which we now understand and have done something about. But still she will leak. This means that their is always water in the main tanks. When it gets hot, the sun heats up the decking and thus the tanks and the water evaporates, the tanks now contain moist air which condenses out all over the place, not a good idea in a wooden boat. Just has the esteemed Mr Leech has pointed out. As we are now using the boat a lot, this means that we leave her all over the place, so we have to leave her locked up so the tanks become a horrid place, rather than nice an airy when we are back at bas and can leave the hatches open.

So what I want is something to keep the batteries topped up, so the bilge pumps will always work, very important that bit! Then because we aren't actually sinking there will be some power left over, once the batteries are full. I wish to use this power and only this power to drive some small fans to circulate the air through the tanks. Small solar panel will power a lot of modern 12v fans and get 6 to 8 changes per hour which isn't bad. But I don't want these fans connected to the batteries just being driven off the surplus energy. They only need to run when its sunny.

Next problem, we are a wooden boat, we do have some metal bits, the ancient bolinder for example, this came fitted with a dynamo, which we have upgraded to an alternator, The system was and is a negative earth system, nearly all the solar controllers are +ve earth, so you can not mount them on anything metal, and you have to watch out for creating earth loops it really gets rid of metal if you do that and that metal is the bolts holding the planks on!!! cant go around with a bit of zinc for each bolt!.

Solutions please!

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cheers Ian Mac

[David Mack]

One solar panel to charge the batteries and another connected directly to the fan? Perhaps not as cheap and efficient as the ideal solution, but simple and reliable.

[Robbo]

If you had the outback controller and use the PWM load output via a solid state relay you could drive PWM fans. Ofcourse this will be only worthwhile if you have quite a few fans and expect to have more wattage in fans than your solar panels can provide.

[smileypete]

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Edited August 25, 2014 by smileypete

[Timleech]

If you used one of these, you could set the fans (output) to be purely timer operated, for the middle of the day when solar input should be reasonable, or maybe for the mornings so that the batteries have a chance to recover in the afternoons. Trial & error probably required here. Also set the load cutoff (over discharge) voltage to the maximum available which is 12.5 Volts. The case appears to be insulated from the electronics, though surely just mounting the controller to an insulating panel would get round that one.

 

Maybe not a perfect solution, but it ought to do the job.

There are probably other controllers which would do the same.

 

Tim

[phill]

nearly all the solar controllers are +ve earth

 

 

cheers Ian Mac

 

It this true? Seems a little odd as all modern RV systems are negative earth.

 

As for your scenario: use a 2nd panel no battery (or a very small one ) connected to the fans so sun = fans and it's independent of the main system. I would probably experiment with a small 20-30w panel no controller no battery and connect fans in series until they run when sunny.