changing from parallel and series

rake1

I have a 12 volt parallel system with a 195w panel one 12v battery an older c35 PWM controller, I want to add another 195w panel but my run is about 50 ft and my wire is # 10 with the other panel I will be pushing 20 amps through the #10 which is to much. Can My C35 handle changing from parallel to series??. If so do I have to do anything special to get this to work?

Photowhit

No, it's designed for panels designed to output charging voltage for a 12 or 24 volt system. If you put the panels in series the voltage goes up but the amperage (current) remains the same. 10 gauge can handle 20 amps, might run your panels VMP through a voltage drop calculator and see how much voltage drop to expect.

https://www.calculator.net/voltage-drop-calculator.html

rake1

Sorry but I am not great at this are you telling me that my controller cannot handle series. You are correct it can be used on 12 or 24 volt.in series My understanding is I will only pull about 10 amps. But in Parallel it will pull 20 amps,hence the question about going to series.

Photowhit

Once you put the panels in series, the charge controller may be able to handle the 35-40 volts and 10 amps (a guess) coming in. but it will NOT be able to output more amperage than it is presented. To do that you would need a MPPT type charge controller. 

InCogKneeToe

I would just add another 10 or 12 AWG run. My C40 can handle 12/24/48V but it's Output is also 12/24 or 48V, my 12V Inverter will always be a 12V inverter.

I run 2 12AWG runs  a 50' and a 35' with 2 100w panels each for 400w@12v and can pull 18A out of it.

rake1

thanks guys so the only way I can go to series is with an mppt correct? If so I may do as you mentioned and add another run of wire.Or consider an MPPT.

Photowhit

Run your numbers through the voltage drop calculator. If it appear too large a drop 4-6%, you might think about how the battery is going to be charged as well. When the batteries are depleted a good bit they will need less voltage, so you will have less voltage drop... When nearing full they will require less amperage so the voltage drop will be less...

I'd hook up your extra panel and see how your system responds. The VMP (working voltage) is usually around 17.5-18 volts, sometimes higher on newer panels. So if you have a 18 volt VMP panel, your drop would be about 2 volts to 16 volts which is high enough to function pretty well. There will be some voltage loss to heat, as well. but perhaps the bulk of your charging will normally be done. I encourage you to run the numbers and think about the charging cycle.



I looked at some available 195 watt panels, Only found EcoWorthy looks like between 18.7 and 19 volts VMP, they would drop about 2 volts so would be okay. 

Photowhit

Ampacity of 10 gauge copper wire is 30amps according to NEC, so no issues there!