Batteries

Naio wrote:

jrnymn7 wrote:

2oldman wrote:
No matter the power curve, ya still gotta put all that energy back!

Yep, and the interesting thing about LiFePo4, is they do not require Full Charge or Floating... so one would have to re-think their solar charging set-up, and have it stop charging once the bank was at say 90%.

I don't believe in the "one size fits all" approach to solar, so I plan on switching things around, occasionally. For example, I won't need 280w of pointed mppt solar during the summer, so I will likely run one flat 140w panel on pwm. But come the colder, darker months, I will run 2 panels pointed mppt. It was considering the charging of lithium batts that got me thinking about dragging out the charging time to suit how much charging was actually needed.

Forgive my ignorance, but why would it be worth the trouble to swap out panel and controller? What would be the benefit?

It would only be a simple matter of switching around some wire connections. The advantage would be not overly charging the bank, unecessarily. The sloar30 pwm I'll be using has the same setting for abs and float. If the bank was full by say noon, it would charge at Vabs until I could deal with it, several hours later, after work. By slowing the charging process, by lowering the charge rate, I could effectively drag out the charging time to say 5pm. Simply put, I just don't need 16 amps for 10-12 hrs a day, to replace say 40Ah's usage. I could just use an mppt year round, and let it float the bank most of the time in summer, but I'm also interested in comparing the performance of the two methods.

Come late fall/early spring, using mppt will be of necessity, as I will likely need to supplement the 280w system with either gen charging and/or by adding an additional 100 watts or so of portable solar. And yes, I could go with a larger array from the get go, but the portable could come in very handy at times as well.

Cloudy rainy weather does a real number on panel Isc, so mppt does much better under such conditions, while in hot weather, panel voltage takes the hit, so pwm can actually do better. Much of my reconfiguring will be in the interest of research... seeing first hand what works best in any given situation.