Down the Charge Controller Rabbit Hole...

[Redbearded]

Hi All,

I've been doing research on charge controllers and I am seeing two very different strategies:

1. Put a smaller MPPT charge controller on each large (~300W) panel like a Victron 100/20 or 75/15 for about $100-130 each. Then rinse and repeat until you get to the desired power. This runs at ~60-70Voc

2. Use a parallel and series array (with like 4,6, or 8 panels) to create a shading tolerant system that runs at a much higher voltage ~150Voc and uses a MPPT controller that you only need one of but it costs like $500-600. An example would be Outback FlexMAX system.

I think the smaller victron setup seems like a newer system and is more modular for our needs in the RV power community, but is there any advantage to using the outback strategy? The only thing that comes to mind is higher voltage leading to less power loss in the lines from the panel to the charge controller.

Any thoughts?

 

[John61CT]

The first approach is also higher voltage.

Second may save wall space, KISS at the bank. Maybe cheaper depending. . .

Are you planning very long distance between panels and bank?

Getting 2-3 gauges in 100' spools saves $ or lets you get to quality tinned marine.

Sell the leftover when you're done.

 

[Weight]

Let's start with how much room do you have for panels? Example; My van can fit 4 Renogy 100 watt panels. Maybe five if I eliminate the roof vent. But then I am working with 12 volt system, not hundreds.

 

[bigskybob]

I went with EP Solar 30amp controllers.4 panels per controller.So far it's working great.

 

[DLTooley]

I believe what you are looking at are two basic well designed types. The first rv, the second residential. I wonder about the 75/15 and whether it will handle a 48v array or if it needs to be limited to 36.

 

[frater secessus]

solar is like cell data. you either need a little or you need a shitload. Nothing useful inbetween

A list of what people are actually doing with solar provides evidence to the contrary.

 

[John61CT]

> wonder about the 75/15 and whether it will handle a 48v array or if it needs to be limited to 36

Why wonder when you can read the specs?

In theory 75 Voc max, but I would stay under 65V.

22A Imp is the other hard limit, but for practicality 220-250W, can go to 300W if the extra power doesn't cost any more.

 

[highdesertranger]

did you actually read what frater posted. I didn't see 2000 watt mentioned anywhere. the list is 100, 200, 300, 400, 600, 1,000 watt. highdesertranger

 

[akrvbob]

I'm actually a fan of multiple controllers for redundancy, I have that right now, however, I don't think it is the most common one. In my experience, by far most people run their panels in parallel into a single properly sized controller.

Every situation is different, chose what works best for your unique situation.

 

[Redbearded]

I'm leaning towards the multiple controllers as well, mainly because they have gotten so cheap, especially for the smaller ones! I was talking to a guy living on his sailboat tonight and he said when he put in his system a while (not sure how long) ago his controller was more than the panel... 

It seems that there are the 2 ways of doing it, and they keep borrowing ideas from the other guys. I know that some places are letting series panel voltages for houses go to 1000V before they are piping it back to the grid. Crazy!

 

[tripper]

BTW Victron has large controllers also. Built in Bluetooth connectivity and upgrades to software/firmware as needed. Full parameter control from android phone/tablet.

I do like the higher voltage from all panels wired in series, especially if it is a long run down to battery banks.

 

[Redbearded]

ITripper, I like that idea as well as long as there is no chance for shading on the panels. the things I have read about partial shading lead me to believe that in a series configuration the losses are pretty ugly! Like 30% and up! When the controllers were expensive I can see that being a real design consideration, but now that they are more reasonable I think I'm favoring one per large panel as well.

I'm also really liking the specs and features on the Victron stuff, I just wish some of the other items weren't so dear... At this point it looks like I'll be running some other inverters. I would love that fancy color display thing... Toys... I may set up an old android phone or tablet just for that purpose, lol.

 

[tripper]

ITripper, I like that idea as well as long as there is no chance for shading on the panels. the things I have read about partial shading lead me to believe that in a series configuration the losses are pretty ugly! Like 30% and up! When the controllers were expensive I can see that being a real design consideration, but now that they are more reasonable I think I'm favoring one per large panel as well.

I'm also really liking the specs and features on the Victron stuff, I just wish some of the other items weren't so dear... At this point it looks like I'll  be running some other inverters. I would love that fancy color display thing... Toys... I may set up an old android phone or tablet just for that purpose, lol.

I handle shading by having a 160 watt portable panel that can be aimed at the sun on a 25ft cord. A 50ft cord would be better. I find the 160 watt aimed right at the sun does a pretty decent job, will pump out around 150 watts throughout most of the day. I park in shady spots a lot and I find the portable panel a must. Very rarely do I have partial shading on my roof, usually it is either no shading or total shading.

On the portable panel I ditched the built in pwm controller that was attached to the panel and wired the 2 x 80 watt panels in series (for 24v) and ran them to one of those cheap 15 amp Victron mppt controllers located near the battery bank. That made a huge increase in amps getting to the battery and minimized voltage sag on the long extension cord. I have seen up to 162 watts out of my 160 watt panels on cool winter mornings when aimed right.