Ok, so here are a few items that I wish I had known about in advance, they would have changed my entire solar experience:
- Not All Batteries are Solar batteries - I cannot emphasis this point enough, no matter how many uninformed people will tell you that their batteries are "Deep Cycle" or "Brilliant for Solar". Unfortunately, true solar battery storage is NOT cheap. Unless the brand is Trojan, and you are prepared to look after them properly, almost NO Lead/Acid or Calcium/Calcium battery that you can use on a Boat or Car is sufficient (or more importantly will last long enough). There are many discussions on this forum regarding batteries and it financially is your biggest and probably the most important purchase. Your Invertor and Panels are cheap in comparison. Especially considering that they are considered almost consumable parts and will eventually have to be replaced... Probably long before your Invertor and Panels.
- Battery Balancers - These are really important (hence near the top of my list). If you can afford to play with the big boys, then go the Victron route, but the price is high. The alternative and still an awesome product is to get something called a HA-02 (available usually from @Chris Hobson on this forum). These things will make sure that even with a small difference in your batteries, you will be able to keep your battery pack in decent shape. In my opinion, these are not optional, you need to keep your batteries in top shape to get the best out of Solar. You can get away with only using 1 sometimes, but rather always get an HA-02 per 4 batteries, no matter the configuration. If you go the Victron route then it depends on product, but still try make sure that EVERY battery is balanced.
- Invest in a good battery monitor - There are a lot of cheaper options out there, but unfortunately I have experienced that the Victron are the best options (702 is the premium in my mind, due to it's temperature monitoring and/or midpoint monitoring). These terms may not seem important right now, but monitoring the mid-point voltage of EACH bank will highlight battery issues incredibly fast, and hopefully way before problems. Contact @Camel for the best prices/availability on the BMV 702's and get at least 1 for each PARALLEL bank of batteries.
You might have seen that my first responses have all been battery related... For a reason, I think and have experienced that batteries end up being the most critical part in any solar setup, and the part that is almost ALWAYS ignored or seen as an after-thought (even by "experienced" Solar installers).
- For God/Budha/Jehova/Siva/Spaghetti Monster 's sake, please remember that you have to have Isolators (seperate from your Invertor) on your PV side, and your Batteries. Any Electrical person remembers the basics of AC, and has AC breakers, etc on the Invertor Input/Output... But DC is also extremely powerful, sometimes more so. An ideal situation is to have a breaker/isolator on every string, but location and cost doesn't always make this possible, so at least have a isolator close to your Invertor. The day you want to work on your invertor and have 400V DC that you have to disconnect, you will understand this comment.
- Still on the above note: HAVE A FUSE! Even if you have a battery Isolator and even a DC Breaker on your battery source, PLEASE, PLEASE, PLEASE invest the tiny cost of basic fuses. They are in your car for a reason, mistakes happen and you do not need a battery exploding in your face. Invest in a rated fuse for EACH of your battery strings, before your isolate or DC breaker. Fuses are not only limited to your Battery DC power, having a rated fuse sometimes on your solar array can save you from oddities, and even sometimes a lightning inducted power surge.
- This one I must admit I don't follow myself, because of reasons, but get surge protectors on both your input AC and your output AC from your invertor. I have been stung, loosing an invertor due to our South African supply, but also cable thefts that have spiked single phase voltages up to nearly 400V AC (watch what happens when theft takes out an Negative bar on a Live Transformer).
- Batteries (again) need to be considered carefully when thinking about your power requirements. There are a lot of tools on the Interwebs to help, but I have found them mostly to be a bit useless because they assume too much. If you want to conserve Lead/Acid batteries for example, then you should try keep their discharge at about 20-25%... And don't trust your Invertor sometimes to tell you that, the closest real values you can get sometimes are from the BMV702's I mention above. So if you have an amazing 400Ah battery bank at 48V, your real power is only about 400x0.2x48 = 3.8kW... But you also have to remember that that power changes depending on the "speed" you take that power out of the batteries. What I am saying is that you might only have 1 hour of household power before they drop out, or if you are extremely conservative and treat the power draw well, you can get 8-16 hours (<400W). Battery draw and the values are extremely complex and I admit that after 2+ years of experience I still battle to follow the logic sometimes.
I really hope this topic gives some newcomers thoughts, but please remember that you are not new or alone to this game. We also have a group of people here with LOADS of experience (AKA Lessons Learned). Please feel free to ask questions, get ideas, and put up your own thoughts. This is a newish technology and many times we have surprised ourselves with new ideas. Enjoy the experience.