Seven tips installing solar panel.

1. Calculate the required load. Lets do a sample calculation.
   1. Lights (2 item) @ 30 W @ 5 hours/day = 300 Wh
   2. Radio  (1 item) @ 25 W @ 4 hours/day = 100 Wh
   
   Total load of 85W and 400wh.

2. Selecting the Batteries

1. Use deep cycle battery. Deep cycle battery can maintain 12V @ 30% charge level while car battery will drop below 12V @ 50% charge level.
2. As our requirement 400wh, we can select a battery with a rating of 12V @ 110Ah which can store energy up to 1,320wh enough for our requirements.

Deep cycle batteries 

3. Choosing our Solar Panel.

1. The lower the difference between the battery voltage and the operating Voltage of the panel much better. This is due to the energy transfer efficieny. Bigger mismatch, lower efficiency. If you more money, you can buy MPPT (Maximum Power Point tracker). For economic reason, choose a panel with high efficiency, close to battrey voltage. A Panel with operating voltage between 15-17 V

  2. @ 400 wh requirement, we assume a 100W/panel.
      For whole bright day, only set 6 hours full solar panel charge.
     
Energy stored by the solar panel:
  100 W * 6 hours =600 wh. This is the energy we gather the whole bright day enough for our requirements.

4. Selecting for inverters.
  1. Choose inverter higher than our requirement (85 W) so any inverter higher than 85 W but  also consider power factor.

                    Inverter rating = 85W/.85 = 100 W rating.

  2. In my experience, I prefer to use computer UPS (unterruptable Power Supply) 1000 VA. I do some trick by replacing the battery inside the UPS to my batteries. UPS has installed combination of inverter and voltage regulator.

5.  Optional for me the charge controller.                                                                    

This will protect from battery overcharging from solar panel charge. In my case, I use my solar energy daily and  infact I'm deficit that I need to run my generator. So I don't install charge controller.  

6. Wiring. Always do shorter connection from your solar panels to your battery to reduce losses.
Use wire  AWG #15 or larger (smaller AWG) much better.

7. Solar panel installation.

Depending on your location, Set the angle of the panel that will get the maximum power from the sun. In my case I set it 20deg tilt facing south. Never interconnect panels with different ratings, it will lower its charge efficiency.
    
         E.g. S1=100 W 24Voc  paraller with S2=100 W 36 Voc  
         S1 will operate at 17V while S2 will operarate at 17V.
         S2 efficiency is operating at 50 % efficiency (waste)