Newbie solar questions

specv510 wrote:
This is for a family of five with three teenagers and we boondock for 2-3 days at a time. Will this system work? If I decided to get two panels would the Tracer 30 amp controller be able to handle them?

I don't remember what the rule is for solar wattage per battery capacity, but I think it was to have about equal wattage per ah? Besides wasting energy, are there other negatives to having too many watts? We are very conservative with our electricity usage, but if we wanted to splurge would having a second panel be beneficial considering the small battery bank?

Will it work? Yes, with some drawbacks. I agree with Don Piano - you should get a remote temperature probe, maybe even a different/costlier controller if you have to. Temp probe is worth a lot more than fancy display of controller. I don't see such probe mentioned on Tracer website - only a built-in temp compensation.

Will Tracer 30 will handle 2*250W? Yes, but with some clipping at peak hours in summer, i.e. you will lose some energy. Not much, 5 percent of daily harvest or less. But, if you connect them in parallel, you need a lot better cable than gauge 8. The beauty of series wiring is that you can use a standard MC4 extension cable, Unlimited Solar have it in gauge 8. Make sure you order a DOUBLE length, because you will cut it in half to make 2 leads each with one MC4 connector.

I see that you're trying to make it on a very low budget, but it would make sense spending more and getting Rogue 3048 with temp probe and everything else included. It's not as cheap as Chinese made and Chinese designed controllers, but it's worth it. Don't know how this Oregon company is able to do it, but I couldn't find a cheaper 30A controller with these features and quality. At 30A there would be same clipping though, no matter what brand.

Is more watts beneficial for battery? Yes, it is, in your case. The "rule" is 1W per 1 AH but this isn't really a rule. With a small battery bank you can (and should) get 1.5-2.0 W per 1 AH, so that it will bring the charge up to 90-100% sooner.

Energy budget is an individual thing. Some people can live on 20 AH a day, some need 120 AH or more. With a family of 5, one 250W will be sufficient if your kids don't over-use their electronic toys - laptops, video games etc. Flat 250W in summer will collect 60 or 70 AH on the best day, and 10-20 AH on a dark day. Your LP fridge alone will need 8-15 AH over 24 hours, so on a dark day 250W will barely cover it even if you don't use any lights, pumps or radio/CD. So the battery will gradually go down, though it won't go down too much in 3 days.

In winter these numbers of daily harvest will be roughly 1.5-2 times lower, while your consumption remains the same or even higher. Get 2*250W if you can.