Basic pv/fan question, compost aeration SOLVED

being slightly electricity illiterate i approach the more knowledge endowed members of this esteemed community… pardon the play with words, it must be the child in me :crazy_face:
i have a small pv and a fan, see images for specs please - i want to directly connect the fan to the pv as part of a compostulator [my wife’s word] which will blow air via pipes underneath garden cuttings to speedup composting.
now it seems the pv might deliver too much electricity to the fan - can i put say tinfoil over parts of the pv to curtail power output?
in anticipation.


I would look at a little cheap buck regulator, that has a range of dc input voltages, and the output voltage for what you need. 12v in this case, for the fan.

Buck regulator

Quick Spec

  • Input Voltage: DC 16V-120V
  • Output Voltage: DC12V
  • Output Current: 3A
  • Output Power: 36W
  • Conversion Efficiency: ±96%
  • Working Frequency: 140KHz
  • Soft Starter: Yes (Failure at high power load)
  • Over Temperature Protection
  • Overvoltage Protection
  • Short Circuit Protection
  • Working Temperature Range: -40℃ ~ +85℃
  • Working Humidity Range: 0%-95%RH
  • Dimensions: 42 x 30 x 17mm
  • Net Weight: 15g
1 Like

Just to add to what Deon has posted.
The PV panel will produce power at 18V while you are using a fan that require 12V. If the voltage is too high it will damage the fan, but there is a bit of tolerance in the fan. If the current that the PV produce is too much it is not critical as it will just not be used, but the voltage can break the fan.
The buck converter will reduce the input voltage to what you want making it safe for the fan to keep working for a long time (hopefully).

hows about i put two of these fans in series?

What Deon said. Likely cheapest and closest to idiot proof.

Could also go completely old-school and put in a series resistor. But it would have to be a beefy one. I expect that panel to run around 20V to 22V open circuit, so you need to burn off 10V or so, at 0.64A, that is 6.4 watts of heat to get rid of, and you need around 15Ω to drop those volts. So one of these, combined with something to sink the heat into…


Go with the buck converter. Much easier :slight_smile:

They will run at 11V each. It could work… maybe…

tx guys, it seems the most cost effective will be to get the right size pv like here - i have just ordered… tx you gave me the right pointer! :raised_hands:

The problem is that the small 12v panel is only rated for max 500mA, while your fan needs 640mA

Quick Spec

  • Rated Power: 6W
  • Operating Voltage: 12V
  • Operating Current: 500mA

The buck regulator is also half the price of the 12v panel, so you could buy two and have a spare on hand, in case it ever goes south.

tx @deon, beteken dit die fan sal stadiger of gladnie hardloop nie?

Ja, die fan sal net stadiger hardloop, want hy kry minder amps as wat hy moet.

dankie, dis nie so krities nie, die fan kan maar net poer poer of ek sal 'n ander fan moet kry… eish, onkunde is duur :see_no_evil: