Solar and battery help

kjenckes wrote:
Good Morning. I am hoping someone can provide a simple answer or 4 for me. I just read a post on the TC forum about flexible, light weight 100 watt solar panels and love the look of this, I have a Northstar 850SC pop up that this would go on. I have plenty of room over the bed end for these with out shadows from roof top stuff. I currently have 1 Interstate SRM-27 listed as 160 RC. (I will be adding a 2nd) I would prefer 31s but am not sure about the space available yet.

#1- Does the 160 RC on the battery mean 160 amps?

No RC is reserve cranking amps; 160 RC implies 95 to 105 aH

#2-50% discharge or 80amps (If #1 is yes) or 12.2 volts is the lowest I want to take this battery on a regular basis, correct? Therefore 2 would give me 160 amps?

12.2 volts is a good choice; two size 27 deep cycles will be 190 aH to 210aH

#3- The listed optimum amps for this 100W panel is 5.7 amps with a max fuse of 10amps. Does this mean that 2 of these on the 20 amp controller is appropriate as the minimum? 30 safer? Could I run 3 on a 30?

Depends on the controller size; fuse sizing is determined by NEC

#4- What is the rule of thumb for minimums watts per battery? I know sunlight hours and shade, etc affect all of this. I see some with 270 or more watts but no mention of how many batteries this supports.

The rule of thumb is 80 to 100 watts per 100 aH of battery



The output of a solar panel will vary quite a bit over time of year and full sun vs cloudy or shade. Max output usually occurs between 10 AM and 3 PM in full sun but this is another general rule. We have two 80 watt panels feeding a TS-45 controller which charges a pair of Exide Stowaway 105 aH batteries. All main lighting is LED, no microwave, TV, or other high usage (wattage) devices. We are very conservative with power usage and get 7 to 10 days before the batteries reach 12.2 volts(60% soc). Connecting the solar panels at that point takes 4 to 6 hours to recover the 40% used.
I suggest an internet search for the 12 volt side of life and a visit to batteryfaq.org.
Wiring between the panels should be as short as possible and no smaller the 10 awg. Batteries should be the same age and wiring from the controller to the batteries no smaller then 8 awg.
If you decide on 3 panels you may find the cost of a mppt controller to be worth while(300 watts is right at the dividing line).

For cpap you want the most efficient your budget can afford if going with 12 volt.