New to solar. 100w kit upgrade to 200- 400w

evh515093 Registered Users Posts: 1
Hi, we have the harbor freight 100w solar kit. Found here:

we bought an additional 100w panel for a total of 200w together. 

Both panels are plugged into this 400w adapter/junction found here:

We might get 2 more 100w panels for a total of 400w.  As of now, I know we need to upgrade the charge controller to 400w. (To future proof).   

We have a 35ah battery from harbor freight found here:

We might get another 35ah battery and hook it up in parallel...  

Do we need to upgrade the battery clamps and cable for 200w/400w?  


  • BB.
    BB. Super Moderators, Administrators Posts: 33,401 admin
    Welcome to the forum EVH,
    I would caution you to not put a lot of money into these Panels... They are (typically) thin film type panels that tend to lose output over time, and only last, at best 5-8 years in the sun (loss of output current). And Thin Film panels have about 1/2 the efficiency of normal mono or poly crystalline panels which last 20-25 years, and (especially in the larger sizes) are usually less expensive than the Harbor Freight kits.
    I suggest that your measure/define your loads (12/24/48 VDC or 120 VAC, Watt*Hours or Amps*Hours*Voltage)--Then design a solar power system around what you need...
    You can design a system around a specific component--Such as your battery... Just to give you an idea, normally a lead acid battery is charged around 5% to 13% rate of charge... So a 35 AH @ 12 volt battery would support an array of:
    • 35 AH * 14.4 volts charging * 1/0.77 panel+controller deratings * 0.05 rate of charge = 33 Watt array minimum
    • 35 AH * 14.4 volts charging * 1/0.77 panel+controller deratings * 0.10 rate of charge = 65 Watt array nominal
    • 35 AH * 14.4 volts charging * 1/0.77 panel+controller deratings * 0.13 rate of charge = 85 Watt array "typical" cost effective maximum
    Of course this does depend on your daily loads and what they are...
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset