Monday, January 24, 2011

DC Amps

The list below shows the actual amps used by various items.

Puck light (LED bulb)     .1
TV Antenna boost          .1
Inverter (Idle)                 .3
Personal fan                   .7
Endless Breeze (low)  1.2     [med 1.8, hi 2.7]
Fantastic Fan (low)     1.2
Dash Radio                   1.2     [low volume]
Light (Auto bulb)          1.5
Fluorescent                  2.9
Furnace fan                  3.5
TV  [12v]                       4.2

How do you use this information?  Let's say that you are using two pucks, two personal fans, FF and your TV.  It is cold out, so your furnace is running about half the time.  Adding the individual amps, that adds up to about 9 amps.  After 3 hours of that, you have used 27 amp-hours.  Now it is bed time.  For the next 8 hours, you are running the furnace only.  That adds 28 amp-hours.  The next day, you run the furnace for 8 hours and the radio for 4 hours for a drain of about 32 amp-hours.

In one day, that would drain about 87 amp-hours from your batteries.  (Realistically, one would probably not have three fans plus the furnace running.  You also need to add load for the refrigerator, water heater, and so on.  This illustration is meant to show how to use amp ratings to estimate the demand on  your batteries.)