Need Help For Quick Connect Port On Cargo Trailer

jwh92020

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I need some advice on using SAE connectors with a portable panel set up on a cargo trailer. We need a 100 amp hr Lifepo4 battery and 120 watts of panel to run a 1.7 cu.ft. dorm fridge and the lights in the trailer. I have access to Some SolarTech 45 watt panels that have are small and lightweight. I'm thinking hat 3 in parallel will get us the required wattage, and because they are aluminum frame panels, not fabric mounted panels, 24/7/365 exposure will not be an issue. What gauge wire do I need for a 25 foot run? I have a couple of sets of 12ga cables & ports, but I've received conflicting info as to whether 12ga is large enough. I've attached the panel specs. We'll be using an Epever 20 amp SCC. Thank you for any help you can give.SolarTech Info.jpg
 

rmaddy

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If that Epever 20A SCC is actually an MPPT charge controller then you should put the 3 panels in series, not parallel. Then you have less than 3A of current from the panels to the SCC. For a 50' roundtrip, 10AWG would be plenty. 12AWG could work given the higher voltage.

If you want the panels in parallel (say for a PWM controller) then for the lower voltage and higher amps you would likely need 8AWG. 10AWG may work but the voltage drop may start getting higher. 12AWG would be close to 10% voltage drop which is way too much given the lower voltage to start with.
 

jwh92020

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The Epever is a MPPT controller. So 12ga would be ok if we went series instead of parallel? I was hoping to use the 12ga cables I have because the lady I'm building it for is on a fixed income and has a $0 budget. Thanks for the info.
 

jwh92020

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Test every connection with a volt meter. Red is not always the positive wire. You’ll see.
Thanks for the reminder. I'm pretty good about testing polarities. Reversing them is not good for inverters (don't ask me how I know)
 

rmaddy

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The Epever is a MPPT controller. So 12ga would be ok if we went series instead of parallel?
What is the max PV input voltage rating for the SCC? 3 of those little panels in series will have a Voc of 66.6V. If the controller is rated for 75V or more then you should have no problem putting 3 in series. 12AWG will work for 25'.
 

jwh92020

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What is the max PV input voltage rating for the SCC? 3 of those little panels in series will have a Voc of 66.6V. If the controller is rated for 75V or more then you should have no problem putting 3 in series. 12AWG will work for 25'.
It says max 60v input. Looks like she's gonna need a bigger SCC.
 

rmaddy

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It says max 60v input. Looks like she's gonna need a bigger SCC.
To put the panels in series, yes.

So it seems you have two choices:

1 - Spend money on a new SCC that can handle these panels in series.
2 - Spend money on 50' of 10AWG wire and run the panels in parallel with the current SCC.
 

jwh92020

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To put the panels in series, yes.

So it seems you have two choices:

1 - Spend money on a new SCC that can handle these panels in series.
2 - Spend money on 50' of 10AWG wire and run the panels in parallel with the current SCC.
I'll talk to her tomorrow and let her make the choice. She can still return the SCC if she decides to go that way. Thanks for all the guidance.
 

rmaddy

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One more option to consider. Use 4 panels. Wire in 2S2P. You can use the existing charge controller since the voltage will be well under 60V. And with only about 5A at about 40V, 12AWG wire should work just fine.

This also has the benefit of providing more power.
 

jwh92020

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One more option to consider. Use 4 panels. Wire in 2S2P. You can use the existing charge controller since the voltage will be well under 60V. And with only about 5A at about 40V, 12AWG wire should work just fine.

This also has the benefit of providing more power.
I was jut sitting here calculating the series/parallel idea. That's the best way to go for many reasons, especially because the panel is cheaper than a new SCC or a 10ga wire set up. Thank you.
 
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