12V :: fan box

2.27.2014 – Thursday

Sure was nice out today… except for the temperature. The sun was warm and bright but the wind dulled my sense of touch to the point that taking off my gloves to gain more dexterity for strapping a car seat into the Honda Pioneer was a foolish decision.

IMG_0308 IMG_0309

But inside the cabin the weather was much the better. Wood heat. Wonderful, radiant, wood heat. A rolling flame softly rising against the glass pane. As much as I could while away the day sinking into the couch next to the fire, the latest cabin project required my attendance in the basement. The Ol’man had already run a surrogate wire up the wall behind the gas stove from the floor to the ceiling – which we would use to pull the lamp cord through and up the wall. In the two weeks previous I was able to acquire some things:

  • $17.62  – KingWin Four Channel Turn Knob Multi-Fan Cooling Controller FPX-001 (LED Indicator for Power On/Off, Control 4 Sets of Fans, 3 Pin Fan Connections)
  • $5.00    – 2x Neodymium Magnets 1/2 x 1/2 inch Cylinder N48 (26 lbs pull force each)
  • $1.51    – 2x Neodymium Magnets 1/4 x 1/4 inch Cylinder N48 (6.3 lbs pull force each)
  • $27.80  – 4x Evercool 60 x 25mm High speed 3 pin fan EC6025H12CA (Dimension (mm): 60 X 60 X 25, Bearing Type: 1Ball Bearing, Speed (RPM): 5000, Rating Voltage (VDC): 12, Power Current (AMP): 0.24, Air Flow (CFM): 26.5, Noise (dBA): 30, Pin Type: 3 Pin Type / 3 wire)
  • $0.85   – 5 amp blade fuse
  • $6.20   – 4x male &  female insulated connectors
  • $0.35   – 1x butt connector
  • $9.00   – 50 feet of lamp cord (18-2 copper stranded, $45/250 feet roll)

I had some extra parts as well – that’s just what was used in the final installation. The actual construction took about 5 hours start to finish with some additional time invested in gathering measurements from the stove. The total for this project was $68.33 and 5 hours.

 The fan box is an alternative to a $260 factory accessory. The factory accessory plugs into exiting connections on the stove and requires access to a 110V outlet for power. The objectives that had to be met by the fan box were 12V DC power, easy installation, ability to use existing wiring on stove, and to force enough air between the fire-box and firewall to increase heat distribution throughout the basement. 12V DC power means that we can heat up the basement without wasting power idling an inverter. The magnets allow for easy installation and adjustments. I purchased wire connectors that mated with the existing wiring on the stove for installation. And lastly, the fan controller allows for each fan to be individually adjusted for output (which is nice for fine-tuning the airflow to noise ratio).

Design wise, the fan box is glued together with a few plugged wood screws. The fans slide in from the open end and all the wiring connections are enclosed.IMG_1786

Sliding everything into the box allows for easy maintenance and fewer screws. The fit is snug so there is no rattling. IMG_1783

Once the cord cover panels and controller plate is slid in the end cap is magnetically held in place by small 1/4″ x 1/4″ cylinder magnets that mate up with screws counter sunk and adjusted for a perfect fit. IMG_0254

The two large magnets are quite powerful. As a test I was able to easily support two hammers over the fan area without failure of the magnetic  bond. IMG_0259

I had thought that a rheostat was pre-installed on the stove, but when I started the install I discovered that there was a space for a rheostat and not actually a rheostat. The stove has an aesthetically pleasing ON/OFF rocker switch for the front flame. The flame turns ON and OFF with the switch, but also turns ON when the stove fires up and starts to produce it’s 20,000 BTU output. I suppose in a house it would be nice to see a constant flame without having the stove run at 100% in order to see the flame. For the time being the switch has been repurposed as the ON/OFF switch for the fans (instead of the rheostat switch like originally planned). The install went reasonably smooth, making this the 3rd 12V accessory added to the cabin after the LED lights in the kitchen and the charging station automotive outlets. Three of the six slots on the 12V cabin fuse block are now in use.


The blue LEDs are visual indicators that the fans are on. They do make sound as well, but if we decide to slot in quitter fans in the future it may be nice to have a visual indicator that something is running. IMG_0300

Two additional accomplishments for today were the replacement of the energy hungry 42″ plasma TV with a much more conservative 42″ LED TV, and the discovery of a battery charger that does not make LEDs on the 12V system pulse. The unofficial drop in power for plasma to LED is from 15 amps to 2.5 amps (multiply by 12V for watts). The charger we now use at the cabin is better designed for utilizing 12V power and uses a constant current to charge batteries instead of a pulse wave. The result is no more voltage fluctuation on our 12V system. The charger appeared in the previous post and is the Nitecore IntelliCharger i4. The charger is able to charge our AA, AAA, CR123a, and 18650 flashlight batteries. A $5 car cable makes it ideal for our charging station. At about $20 street price, it replaces the Lacrosse BC-700 Alpha that we’ve been using with a 12V to 3V automative transformer and charges the batteries in about 1/3 the time – still acceptable to promote longevity of the battery, yet quick enough to provide a useful upgrade to the current charger.


Now at night we can charge our flashlight batteries, have only the 12V kitchen lights on, and watch shows on a 42″ LED TV and only use a total of 6.5 to 7 amps! (or about 80 watts). Add just 0.5 more amps and the basement can be warmed up using the fan box to push hot air out of the gas stove. IMG_0298


Remember how I mentioned it was cold? It reached 0.0°F at the cabin in the sun. Right now, at midnight EST it is -21°F and dropping (without windchill). This is a winter for the record books. I’m glad I’m not a yearling deer this winter.

4 thoughts on “12V :: fan box

  1. Duncan Cochran

    Hi. Love your site – interesting stories, but can you tell me where you got the nice 12v sockets under the shelf with the Nitecore charger?

    1. offgridcabin Post author

      The outlets are prime products mini 12-V outlets. I don’t remember exactly where I got the outlets but it was likely either amazon or a marine products website.

    1. offgridcabin Post author

      The propane heater/fireplace optional fan ($260) pushes air up along the back of the heater and out the front through a duct. My home-brew fan unit works on the same principle. The heater is also located in the basement.


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