switch to use my spare electric to power a 12V fan

[simonfraser]

i want to ventilate a bow locker and often have spare electric to power a computer fan
12V bow battery in the locker - automatically being topped up as needed

the switch will need to connect when the voltage is above around 13.5V - need to be able to adjust this a little

surely some one makes this ??
but not getting very far googling - obviously not putting the right words down

who can offer a solution ?

tnx

 

[B27]

I'm not aware of any products, which is not the same thing as the products not being there.
I'm looking to use the excess solar power when the battery charging goes into 'float', to run a hefty 'computer type' fan. There are few ways of doing this, you could sense when the panel volts go high and switch the fan on. You could have some kind of output from the battery charger.
We have been kicking some ideas around, based on using an Arduino type microcontroller to monitor the batteries and maybe do other stuff.

 

[PaulRainbow]

Adjustable VSR

 

[noelex]

Some solar controllers, such as the Victron models will do this.

Wire the fan to the load output and set whatever volltage is appropriate.

 

[Bristolfashion]

Buy User Programmable 12V Dump Load Controller | REUK.co.uk

 

[Neeves]

Buy User Programmable 12V Dump Load Controller | REUK.co.uk

If you are 'adding' a computer fan to a fridge, say to remove the warm air at the back of the fridge or to introduce some fresh air from the bow (and I do note that the OP wanted to 'air' a cabin) then the simplest and cheapest is simply to wire the fan to the supplied fan on the compressor and use air-conditioning ducting. The supplied fan is usually connected with simple spade connectors.

Jonathan

 

[simonfraser]

Buy User Programmable 12V Dump Load Controller | REUK.co.uk

thank you, perfect 'dump load'

 

[B27]

Buy User Programmable 12V Dump Load Controller | REUK.co.uk

That's neat, but it doesn't go up to a high enough voltage to determine when the solar has excess power.
I don't want to dump power when my solar is charging at 14.4 Volts, I want to use excess power when charging the batteries is not fully loading the solar. I can detect that by the solar voltage going up above the V(peak power) of about 18V. Possibly the power will mostly be dumped when the battery is full and the charge controller has turned the wick down to 13.5V 'float'?

 

[noelex]

That's neat, but it doesn't go up to a high enough voltage to determine when the solar has excess power.
I don't want to dump power when my solar is charging at 14.4 Volts, I want to use excess power when charging the batteries is not fully loading the solar. I can detect that by the solar voltage going up above the V(peak power) of about 18V. Possibly the power will mostly be dumped when the battery is full and the charge controller has turned the wick down to 13.5V 'float'?

This is one of the advantages of using the load function of the solar controller. The Victron units even have clever algorithms such as "Battery life" which aims to run the load, but will preserve the battery as much as possible, including getting it charged to full every so often to prevent sulfation.

There is a range of functions that can programmed to perform useful tasks.

 

[Bristolfashion]

That's neat, but it doesn't go up to a high enough voltage to determine when the solar has excess power.
I don't want to dump power when my solar is charging at 14.4 Volts, I want to use excess power when charging the batteries is not fully loading the solar. I can detect that by the solar voltage going up above the V(peak power) of about 18V. Possibly the power will mostly be dumped when the battery is full and the charge controller has turned the wick down to 13.5V 'float'?

12V 24V Digital Voltage Sensing Relay 10A - battery protection -- dump load -- auto switch battery banks

Looks like this accepts values between 0 and 99v!

 

[VicS]

12V 24V Digital Voltage Sensing Relay 10A - battery protection -- dump load -- auto switch battery banks

Looks like this accepts values between 0 and 99v!

 

[Gsailor]

thank you, perfect 'dump load'

That is indeed a useful little circuit.

I built one (using instructions from somewhere - internet or YouTube I think) that sent the excess current to a secondary battery via a rely.

My crew used to worry what the clicking noise was, but I told them it was just the relay.

For £11, I would not have watched, learned, soldered... etc