Analysis of solar power system by Kee Byrd,  12 Feb, 2011


Based on 700mA  idle all day and 10A transmit 15 min/day
 
.7A x 12v= 8.4W
8.4W x 24 hr= 201.6 whr/day
 
10A x 12V = 120W
120W x .25 hr = 30 whr/day
 
201.6 + 30 = 231.6 whr/day
 
   Battery
232 whr/day /12vdc =19.3 Ahr
allowing for 2% wiring losses and 80% depth of discharge x 5 days autonomy
 
19.3 Ahr x 5 / .98 /.8 = 123 Ahr  @ 12VDC
 
Battey = > 123 Ahr
 
   PV  Array
 
232 Whr/day
allowing for 10% battery charging and discharging losses
also 2% wiring losses
 
232 / .9 / .98 = 263 Whr/day
 
If using a MPPT charge controller and assuming an array wiring and charge controller efficiancy of 96%
263 Whr/day / .96 = 273 Whr/day
 
Allowing for 12% array losses due to elevated temp, soiling, etc
273/.88= 310 Whr/day (at standard test conditions  STC)
 
Array mounting = latitude + 15 deg for winter sun = 36 deg + 15 deg = 51 deg tilt facing south with no shade.
 
allowing 4.2 peak sun hours per day (winter) for our latitude
 
310 Whr/day  divide by 4.2 peak sun hrs = 73.8W
You can substitute values for amp draw or transmit time as needed if they change.
 
PV module = > 73.8 W
 
Modules for 12 V charging usually put out greater than 18 vdc....be aware of the max voltage and current that the charge controller will accept.  Charge controller should match battery type and be temp compensated.  Low voltage shut off is important to protect the battery.
 
 
Did this kinda quick..I will review with you again before you purchase.  FYI  we are finding more and more resources for purchasing solar equip.
 
TNX,
Kee