Adding a portable panel to roof mounted panel

grizzzman wrote:

BFL13 wrote:

grizzzman wrote:

hammick wrote:
I called Renology about their 100w briefcase system and they told me that if I put a 100w panel in parallel with my 160w panel my 160w panel will attempt to match the power of the 100w panel effectively giving me 200 watts. Does this sound right?

I just did some quick research and it sound like the Renology tech doesn't understand parallel connections. He would be correct if I was going to connect a 160w panel and a 100w panel in series. Is my logic correct?

IIRC you are using a PWM controller if this is the case you will get 260 watts but...if you are using a MPPT controller he would be correct.

Can you explain that please? I can't figure out what difference the MPPT makes. There could be a difference between series and parallel connecting the panels of course, where PWM would not work in series except with a 24v battery bank.

If you are using an MPPT charge controller, mixing panels of different voltages and/or currents within an array will have an adverse effect on the entire system. Different module outputs make it impossible for the controller to determine the optimal operating voltage and current because they will be different between the different types of panels.

In fact this is one of several reasons i chose PWM over MPPT. My system will grow over time and i don't need to be concerned about if panels match.

Got it now, thanks. Yes their Vmps must be similar or the MPPT will go crazy. I didn't check to see how close the OP's Vmps were. Also I don't know how close they have to be so the MPPT does not go crazy.

However, he could still do MPPT with the panels in parallel as a 12 I think.

PWM does give you some wiggle room for panel Vocs (Vmps don't mean anything with PWM) in parallel to work together.