PV array

most pv problems are human related.  either on the design side or the installation side.  trackers add a moving mechanical element for a tradeoff in higher efficiency, that is up to the designer.  trackers aside, most problems arise from bad design and or bad installation.  assuming those are not a problem, i would say batteries are the first things to go in systems where they are necessary.

james
Alt-E staff

You really have to do some number crunching and proabably a little guesswork to figure out the size of your battery array.  A little too big is A LOT BETTER than a little too small.  I bought an electric-converted Chrysler PT Cruiser last year to learn about EVs.  The guy that did the conversion did a decent job, but he really fell short on the batteries.  I took them a little too close to their limit driving into town and back and utterly destroyed them.  They were useless after that trip, and held only 75% of their charge after that.  I ended up buying a set of Trojan batteries after that, and took better care not to over-extend them.  They were still running great when I sold the car to begin work on my longer range EV.

So cliff-notes version: spend $900 on batteries when you should have spent $1200 means you just wasted the $900 and you'll STILL have to spend the $1200.

If you don't get close to draining the batteries, it's not a waste.  They'll last all that much longer (with proper care, of course).

I finally found the answer so not need to answer.
David