Please check my math
I put together a small system for a storm shelter.
2 ea group 29HM / 675 CCA / 205 min reserve capacity deep cycle batteries
A 100 watt Renogy panel on a tilt mount
A 10 amp Renogy wanderer PWM charge controller
This was originally put together as a power system in case the storm shelter was in use, day to day there was not a load.
Now I would like to add a 20 watt led light, on a timer for six hours a night.
Does the math below seem right?
2 group 29 deep cycle batteries = 410 min of reserve capacity = 170amp hours
170 / 2 = 85 amp hours to 50% discharge.
85 / 2 ( days) =42.5 amp hours (cloudy days)
100 watts de-rated to 80 x 4 hours of sun = 320 watt hours / 12 volts = 26.6 amp hours
20 watts x 6 hours = 120 watt hours, add 10 more for the timer =130 watt hours.
130 / 12 volts = 10.8 amp hours