How to power a fan only when solar is charging.

[TURNKEY]

I want to run an exhaust fan from my battery compartment to vent out hydrogen during charging cycles but I don't want it to run 24/7 as I do now. I tried powering a computer fan off my panels before the charge controller but the charge controller allows power back to the panels when they aren't charging, like at night.

The reasons I want to do this are:
-battery compartment is not that air tight and will be hard to make it so-I don't want the off gasses getting into the trailer.
-it is just a small draw..but watts are watts
-I like to do tiny tinker jobs like this one (I just installed thermostatically controlled fans in my fridge chimney)

One way would be a separate tiny panel just for the fan-expensive. Or some kind of voltage controlled switch (panels run at +17 volts when charging).

I'm running 200 watts on the roof and another 100 watts on an umbilical. Batteries are 2x225 amp golf cart bats. We almost exclusively dry camp. We do not have an inverter and run the genny once a month or less.

Any input or ideas would be welcome.

[loggenrock]

Why not just power the old computer fan direct from the solar INPUT leads? Would only run when they produce power - it should tolerate higher voltage (we're talking , what, 17VDC?) fine - just spin faster!

[Ed_Gee]

I would consider a small muffin fan. They provide plenty of air circulation yet they only draw 0.1 Amps. No need to auto control it at all....just hook it up to the battery bank and let it run 24/7.
12V muffin fan

[shastagary]

a under voltage switch like this would work under voltage switch module
set it to just above the battery resting voltage.
or this? 12V Battery Low Voltage Cut off Switch

[TURNKEY]

I'm not gonna buy a new controller just to satisfy my whim of having the fan not run at night:R

What about the voltage from the panel being high vs a battery? Could I build a voltage controlled switch?

[time2roll]

After browsing the manual.... I don't think that excellent controller will do what you want.

You would need a controller with 3 sets of terminals. Solar, Battery, Load control.

I would be tempted to go with a Trik-L-Start combiner that would normally connect power to your chassis battery when charging voltage is available. It will pass 5 amps so it should power the computer fan just fine.

http://www.lslproducts.net/TLSPage.html

[GordonThree]

TURNKEY wrote:
Aren't I already connected to the load connectors? The fan is presently wired to the wires running from the panels to the controller. It is not connected to the battery directly.

Check your instruction manual. There's the solar input, a battery output and a programmable "load" port for controlling small loads like a light or fan.

Hopefully someone with a TriStar can chime in with details.

Looks like not all models have a load port.

[GordonThree]

Dupe

[BFL13]

TURNKEY wrote:
Aren't I already connected to the load connectors? The fan is presently wired to the wires running from the panels to the controller. It is not connected to the battery directly.

No. The "array" wires are for input from the panels and the other two sets of terminals are for output. One to battery and the other to loads.

[TURNKEY]

Aren't I already connected to the load connectors? The fan is presently wired to the wires running from the panels to the controller. It is not connected to the battery directly.

[GordonThree]

BFL13 wrote:
Will the fan run off the controller's load terminals, while the charging is from the battery terminals? You can usually program the timing of the loads on the load terminals of a controller.

X2 for using the load terminals

See here for more info

http://support.morningstarcorp.com/faq/

[BFL13]

Will the fan run off the controller's load terminals, while the charging is from the battery terminals? You can usually program the timing of the loads on the load terminals of a controller.

[wanderingaimles]

Maybe a small 12 volt battery and 10 watt solar panel just for the fan.
Since that separate circuit would only charge when the panel gets light it should largely mirror the main system and only power the fan when the main system needs it.

[TURNKEY]

It's a Morningstar Tristar 45 (shout out to Handy Bob) It does not discharge at night as I run a Trimetric meter and it shows no loss.

[Lwiddis]

I too can’t remember any controller that allowed power back to the panels, and I wouldn’t enclose a wet cell battery and rely on a fan.

[time2roll]

TURNKEY wrote:
I tried powering a computer fan off my panels before the charge controller but the charge controller allows power back to the panels when they aren't charging, like at night.

Very unusual for a controller as that is one of the primary functions to prevent discharge at night through the panels.

That said I would be looking for a new controller with a programmable load control circuit.