30W cooling fan via inverter

Hi T.R,
I don't know the calculations but here are some real world figures from our setup when we tested. We run a 3 speed 240v 50w fan via a 100w can inverter in the CT & the drain on the deep cycle is;
100w inverter no load = .2amp
Fan on via inverter;
Low = 4.5
Med = 4.7
High = 4.9
If you turn on the rotation grid it use's a extra .3amp on all settings.

Cheers Simon.

Hi,

Not too sure about your formula, but it works like this:

First - your battery appears to be rated at 130Ah, so from fully charged it should provide about 130 amps x hours before being totally discharged. That's under ideal conditions, and in practice you won't get that much. Also, battery life is reduced if it is allowed to 100% discharge. (If it is fully discharged it is important to recharge immediately to avoid serious reduction in life.) To be reasonable, assume that your battery can safely provide say 110 amps x hours (that's 1 amp for 110 hours, 2 amps for 55 hours, 3 amps for 36 hours etc.)

The current drain - Regardless of voltage, a 30 watt fan will require about 30 watts, more on starting and running fast than when it is running slowly. Watts = volts x amps so 30 watts at 12 volts will require 30/12 = 2.5 amps. Depending on the size and technology of the inverter, it will be about 80 - 90% efficient, so the current drawn from the battery will in fact be closer to 3 amps. (This is just theoretical stuff - in practice, give or take 25%). On this basis your battery should run the fan for 36 to 48 hours if there is nothing else drawing current from the battery.

HTH

John

Consider getting a 12cm (120mm) 12 volt brushless motor computer fan with ball bearing mechanism, square shape about 1 inch deep, and using that. You can balance it on a flat surface or mount it on a base plat etc., but keep fingers well away. You can get a fan blade guard for them for around $7 if you wish. get 2 guards if you want, one for the fron & one for the rear.
These fans run at about 2000 r.p.m. and move quite a bit of air. Try one out in the shop before you buy.
They draw between .4and 1.5 amps. depending on make etc. Some come with a speed control using a little knob which is normally placed in one of the desktop computer tower rear slots & enables the operator to adjust the fan speed from about 300 rpm to max (say 2300rpm or so). Faster = more air & more noise. Those models may also have a temperature control which in normal situation senses the CPU temperature and speeds up the fan depending on how hot the CPU gets. No need to connect that part.
Cost of a basic 12v brushless motor fan would be $20 to $25, or up to $40 for a sophisticated one.