ya, a computer fan could work. but then you could get a 120volt transformer to 12volt d.c from your local computer shop i use princess auto got crap for farmers...i did this on my first setup years ago and was unhappy i was only using 2 mothers in an inclosed box of 3 by 4 by 2. if your going to use them and can afford 5 bucks go get a step down transformer will save u many hours of bullshitting car battery's.