RV- Upgrading system -Parallel vs Series Panels/MPPT vs PWM?

[WharfRat48]

Posted on the newbie forum, but did not get any responses.....Switching to 200AH lithium on my travel trailer and need to purchase a new charge controller. Which got me thinking, should I be switching my 3 x 100W panels from parallel to series and getting a MPPT? Or should I stick with my parallel panels and a PWM controller? Is there an advantage to run a MPPT with panels in parallel or is it a waste of money? Since this is a mobile application, panel shading will come into play most of the time. Is there a standard "most efficient" build for mobile (shaded) applications? Thanks

 

[DerpsyDoodler]

Posted on the newbie forum, but did not get any responses.....Switching to 200AH lithium on my travel trailer and need to purchase a new charge controller. Which got me thinking, should I be switching my 3 x 100W panels from parallel to series and getting a MPPT? Or should I stick with my parallel panels and a PWM controller? Is there an advantage to run a MPPT with panels in parallel or is it a waste of money? Since this is a mobile application, panel shading will come into play most of the time. Is there a standard "most efficient" build for mobile (shaded) applications? Thanks

Yes. if shading (or partial shading) is a concern, parallel is best. if you run in series and one panel in the series gets shaded, it will drag down the voltage of the entire string.

 

[Zil]

It was suggested to me 400W solar or less is fine with PWM. So I did. A first class PWM 45 ampere by MorningStar. It has custom settings for my LiFePo battery bank. It has not been a problem that I see.
Today I would have my 4 100W panels as 2s x 2p with a MPPT controller. Again I would use quality such as MorningStar.

 

[WharfRat48]

Thanks for the replies..... If I go with parallel (12V) panels (due to shading) would there still be an efficiency gain from a MPPT controller or would a PWM controller be more efficient? (not considering the price difference between controllers)

 

[DerpsyDoodler]

Thanks for the replies..... If I go with parallel (12V) panels (due to shading) would there still be an efficiency gain from a MPPT controller or would a PWM controller be more efficient? (not considering the price difference between controllers)

no. MPPT require higher input voltage (I don't remember the factor) than the battery they're charging to work effectively. PWM is what's needed for your use case.

 

[12VoltInstalls]

Today I would have my 4 100W panels as 2s x 2p with a MPPT controller.

still be an efficiency gain from a MPPT controller or would a PWM controller be more efficient?

The advantages of the mppt with panels 2S2P are that in less optimal light the mppt can get enough panel volts to get some charge for one; and by having the parallel arrangement you can thwart the ‘shading’ issue if one string has good sun and the other does not.
When I switched over from pwm (which did great for several years) to mppt I noticed immediately I got charge a bit earlier in the day. The string voltage was useful.

I’d grab one more 100W panel and go mppt, but if your pwm is good for 30A of panels that would work. Efficiency is sometimes not exactly the right question.

 

[WharfRat48]

I guess what I am trying to determine is if I would get "better charging" if I were to switch my 3 panels to series and get a MPPT CC or keep my current parallel set up and use a PWM designed for Lithium battery charging. From what I can tell the answer is "it depends" on the application--- if panels are shaded PWM (w/panels in parallel) would probably be as (or maybe more) efficient as MPPT (in series). But if in full sun, the MPPT would be the way to go. I may just go with the MPPT with panels in series so I have the option of adding another panel in the future as suggested. Does that make sense?

 

[DerpsyDoodler]

I guess what I am trying to determine is if I would get "better charging" if I were to switch my 3 panels to series and get a MPPT CC or keep my current parallel set up and use a PWM designed for Lithium battery charging. From what I can tell the answer is "it depends" on the application--- if panels are shaded PWM (w/panels in parallel) would probably be as (or maybe more) efficient as MPPT (in series). But if in full sun, the MPPT would be the way to go. I may just go with the MPPT with panels in series so I have the option of adding another panel in the future as suggested. Does that make sense?

I think it does. Being mobile, I think more often than not you have the option to choose where to park. You can look for a place with good sun exposure. This assumes you don't have other components on your RV roof that may shade 1 or a few panels at different times of the day.

 

[Zil]

I would first add the fourth panel. Stay parallel with the existing PWM. Later maybe upgrade the controller if you find you need more battery charge. But my opinion is with my small aray, it isn't enough to care.

 

[Paul_R]

Very seldom is shading not a concern with a camper in my experience. I would not set up a camper with series connected panels.

 

[WharfRat48]

I agree - so if in parallel, should I just get a PWM that can be set for lithium? My current CC does not have a lithium setting, so I will be buying something.

 

[12VoltInstalls]

If you’re going to buy something buy the fourth panel and a 3OA mppt charge controller and use 2S2P

 

[mikefitz]

Any MPPT controller will be more effective at charging the batteries.
Three 100 watt panels with a PWM controller will deliver a maximum of around 16 amps. With a MPPT controller the maxinum will be upto 25 amps depending on charge volts and panel temperature, typically expect around 20 amps.
Apart from getting more from the panels, a MPPT controller will have preset or user set charge profiles that will charge the batteries is a safer and more efficient way.
I have yet to come across a PWM that is able to charge correctly.
If you stay with 3 panels and a MPPT controller, wire in series, if you add another panel, two series strings of two panels connected in parallel.
I suggest a 30 amp MPPT controller for 3 or 4 panels, I recommend the Victron 100/30 smart.

Mike

 

[12VoltInstalls]

yet to come across a PWM that is able to charge correctly.

The clone-with-decent-settings P30L I had did great for me over several years.

But when I went to mppt 400W was way more effective at early reaching of full charged battery volts