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

Registered Users Posts: 1
Hi, we have the harbor freight 100w solar kit. Found here: https://www.harborfreight.com/100-watt-solar-panel-kit-63585.html

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

Both panels are plugged into this 400w adapter/junction found here: https://www.harborfreight.com/400-watt-universal-solar-connector-68689.html

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: https://www.harborfreight.com/12-volt-35-amp-hour-sealed-lead-acid-battery-64102.html

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?

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...
-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset