How long for solar suitcase extension before going bigger than 10awg cable?

[hotcoldsummer]

I'm thinking of adding a 100w HQST panel to my current roof-mounted 100w HQST panel w/similar specs and combining both in parallel going into my MPPT controller. Understanding that any voltage drop in the suitcase will affect both panel's efficiency, how long a cable can I make before I need to bump up the cable gauge?

Am I correct in assuming the amperage would drop before the voltage so up to 35' would be ok for 10AWG wire?

I'm only using two different model panels because the flexible panel I have on the roof isn't ideal for a suitcase.

These are my specs:

Roof Panel:

HQST 100 Watt 12 Volt Waterproof Flexible Monocrystalline Solar Panel​

• Max Power at STC ( P max ): 100W
• Cell Efficiency: 22-23%
• Open-Circuit Voltage ( Voc ): 23.5V
• Optimum Operating Voltage ( Vmp ): 19.4V
• Optimum Operating Current ( Imp ): 5.2A
• Short-Circuit Current ( Isc ): 5.51A
• Operating Temperature: -40°F to 194°F
• Maximum Series Fuse Rating: 15A
• Max System Voltage: 600VDC ( UL )
• Weight: 5.3 lbs
• Dimensions: 43 x 23 x 0.8 in

Suitcase Panel:

HQST 100 Watt 12 Volt Monocrystalline Solar Panel​

• Max Power at STC ( Pmax ): 100W
• Max System Voltage: 600VDC (UL)
• Optimum Operating Voltage (Vmp): 18.0 V
• Open-Circuit Voltage (Voc): 21.6V
• Optimum Operating Current (Imp): 5.56 A
• Short-Circuit Current (Isc): 6.5A
• Temp Coefficient of Pmax: -0.23%/ºC
• Temp Coefficient of Voc: -0.33%/ºC
• Temp Coefficient of Isc: 0.05%/ºC
• Weight: 13.2 lbs
• Dimensions: 32.5 x 26.4 x 1.18 in

 

[Tomthumb62]

18v at 5.56A at 35’ (70’ round trip) will incur a 5.14% voltage drop. You lose about 1V.

At 45’ (90’ RT) you’ll get 6.61% drop, or about 1.2v lost.

If you upgrade to 8AWG, you get 3.37% and 4.34% respectively.

 

[hotcoldsummer]

18v at 5.56A at 35’ (70’ round trip) will incur a 5.14% voltage drop. You lose about 1V.

At 45’ (90’ RT) you’ll get 6.61% drop, or about 1.2v lost.

If you upgrade to 8AWG, you get 3.37% and 4.34% respectively.

Ok, great thanks.

 

[Tomthumb62]

Ok, great thanks.

Don’t do what I did. Use 100% pure copper wire. Don’t fall for the cheap price of CCA (copper clad aluminum), which doesn’t conduct electrical current nearly as well for the same size wire. Plus it’s rather stiff and doesn’t coil up very easily.

 

[Mirlen]

Don’t do what I did. Use 100% pure copper wire. Don’t fall for the cheap price of CCA (copper clad aluminum), which doesn’t conduct electrical current nearly as well for the same size wire. Plus it’s rather stiff and doesn’t coil up very easily.

If you're looking on Amazon the BougeRV stuff seems decent and they offer 12/10/8 AWG without connectors, connector one end and crimp your own included or connectors on both ends. Cable is actual PV wire, can't comment on connector quality yet. Strands are tinned copper. Happy so far with mine.