Solar Panels to Controller - Breaker

[scarpenter002]

I am in the process of designing an RV solar system, 400 - 800 watts of panels, connecting each pair in series, then grouped in parallel. Wire from the roof to the controller will be 8awg. My controller will be an EPEVER 80 amp MMPT w/ MT50 remote meter. Based on the configuration, I was calculating approximately 35 amps at 24 volts (800 watts of panels). Just wondering if there would be any issue installing a breaker between the controller and the panels, to allow for the ability to shut off current from the panels?
If yes, would a 40 amp breaker work? (I may start with only 400 watts, then add another 400 watts.)
My controller will be in my 5th wheel basement, where I will have easy access to the breaker.

Thanks for your input.
Scott

 

[gnubie]

It's always good to be able to safely disconnect solar from the charger. A 40 amp breaker would do the job, just make sure its a good quality name brand not a cheapie. The cheapies often have problems, contacts going open / high resistance. There are teardowns of some of them on youtube and it's a miracle they don't spontaneously combust. What's your panel's statistics and how many will be in series and how many sets in parallel? 35 amps seems like a lot of current but might be correct depending on the configuration.

 

[scarpenter002]

Here are the statistics per panel:

Maximum power (Pmax)​	100W​
Voltage at Pmax (Vmp)​	17.2V​
Current at Pmax (Imp)​	5.82A​
Open-circuit voltage (Voc)​	21.6V​
Short-circuit current (Isc)​	6.56A​
Temperature coefficient of Voc​	-(80±10)mV/°C​
Temperature coefficient of Isc​	(0.065±0.015)%/ °C​
Temperature coefficient of power​	-(0.5±0.05)%/ °C​
NOCT (Air 20°C; Sun 0.8kW/m² wind 1m/s)​	47±2°C​
Operating temperature​	-40°C to 85°C​
Maximum system voltage​	1000V DC​
Power tolerance​	± 3%​

As mentioned above, I plan to put each pair (2) in series, resulting in maximum of 4 pairs. Then wire the 4 pairs in parallel. Looking at the above, maybe my maximum is closer to 24 amps, rather than 35 amps... (my calculation was based on 100 watts and 12 volts...)

 

[gnubie]

2 in series (6.5 amps shorted) x 4 pairs would get you let's call it 27 amps. The series part would result in VoC of approx 44 volts for the array.

If it's a genuine one this would handle it but I'd probably go for a higher current rating as things tend to warm up if you push them to the max.

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