Solar Panels Brands - does it matter?

steveexplorer wrote:

Are posters referring to the Tristar MPPT controllers?

MPPT is not a brand or model, it's an algorithm that allows maximum power tracking (not to be confused with panel tracking when panel rotates and follows the sun), and allows using 24V panels with 12V batteries. There are many MPPT controllers besides Monringstar Tristar, and 45A is waaay overkill with 200-300W array. US made Rogue MPPT 30A is cheaper, and still a little overkill. Despite my mistrust of Chinese MPPT clones, there seems to be a good one among them, called Ecoworthy 20A, should be alright up to 300W. Definitely a clone, but I can't say of what. The case looks like Rogue.

I don't know how you are going to make a 200-300W array of a few 24 panels. They all start with 200-something watts, so it would have to be one panel, big and heavy. 250W panel weighs over 40 lbs and at that size it feels like 60 lbs. Very difficult to handle on the roof, not much room to walk around it.

There is no hidden inherent benefits to 24 panels, other than obvious lower current (= thinner wire can be used). It's all about wattage. If you need more power, you need more nominal wattage, and if 2*12V will fill the available space better than one 24V, i.e. more nominal watts, then get 2*12V.

steveexplorer wrote:

Is mono or poly the better performer in low light and/or winter sunlight when panels lie flat?

No difference between mono and poly. Flat panel on a sunny December day in SoCa will harvest 50% of what it can during a summer solstice. That's why, if you want to rely on the solar most of time and it has to be flat, you need to get as much nominal wattage as possible. In summer you will have more than you need, but in winter you will have just enough. Most RV installations are "almost flat" - slight angle is needed to drain the rain and dust off, so conforming the roof slope creates such an angle.