So you chose a battery type. Hopefully after discussion and research. Now what?
Wiring a battery bank is not as difficult as it sounds, but you should be cautious and take your time if you have never worked around electricity. Please wear protective equipment (gloves, eye protection) and avoid dropping anything across the terminals that would create an arc (electrical discharge between opposite posts.)
In this article I am going to simply provide a variety of diagrams with some basic detail to point you in the right direction. A picture is worth a thousand words.
So let's look at amp-hours (AH), and as you can see in the diagram above there are four 12 volt batteries in a row. Each of the + (positive) terminals on those batteries is connected and eventually at the end of that string a single positive red line indicates the cable that carries positive current up to the solar hardware - namely your inverter. The same is true with the - (negative) terminals. When you have like terminals bridged as shown the amp hour rating for each battery is additive. That means if each battery is rated at 100 Amp Hours the entire bank produces 400 AH. This is a good example of a simple parallel battery bank at 12 volts. On this system you would need a 12V inverter to convert the output into alternating current if you plan to run a house on AC (or any structure like a garage).
battery bank in series
Now let's look at batteries in a series. In the diagram above you see one major change. You still have a black negative cable on one end and a red positive cable on the other. Here is the difference (please pay attention). Unlike a parallel system the positive and negative posts between these two batteries are connected. So in a series you are connecting the opposite charged DC posts in essentially a string. When wired in this way you now have DOUBLE the voltage (V) and keep the same amp hour rating across the bank (which in this case is 120 AH).
Confused yet? basically when wired in parallel you are building a larger battery (a bank is simply a group of batteries connected to produce a larger battery) with deeper reserves of power at the same voltage. When you wire in series you are increasing the voltage itself. Think of voltage as the pressure from an electrical circuit's power source that pushes electrons (current) through a loop. In short voltage = pressure, and is measured in volts (V).
Volts and Amps are both measures of electrical current or flow of electrons. Amps, however, are a measurement of the VOLUME of electrons. One ampere is equal to one coulomb of charge which is mathematically equal to the 6.242 X 1018 times the elementary charge. Ok now that I lost you let's look at series and parallel.
batteries in series and parallel
Now we have four batteries. Even better we have both series and parallel. In this example we have both increased the amp hours and increased the voltage. So now the push and reserve load for the battery bank are greater. Most battery banks in the last few decades looked similar to this. So in summary you have a 24V battery bank and a 240 AH capacity because you have now basically taken two sets of two batteries in a series and paralleled them to increase the AH. Now that your mind is getting around the basics lets look at a whole series of possible combinations. Keep in mind that in each case the inverter, charge controller, all have to match the battery bank. The battery bank is the foundational piece of your solar system.
24V battery bank in series and parallel
Now we're getting somewhere. In the diagram above you have 600 AH for loads (draw for devices) and your system is now operating at 24V. We have three pairs of 12V batteries. Each pair is wired in a series to generate 24V. Then those three pairs that now create 24V are wired in parallel to create 600 AH at 24V. Next let's look at a 48V Battery Bank.
48V battery bank in parallel and series
In the diagram above the overall voltage equates to 48V and the Amp Hours are configured to a capacity of 450 Amp Hours. Many of the current systems installed to industry standards out on the market are 48V. Keep in mind that exotic chemistry batteries such as Nickel Iron (Ni/Fe) are typically designed to run in a simple series (which is desirable if your AH are at the right capacity). For example Iron Edison's Ni/Fe battery banks require 20 x batteries at 1.2 V per battery which can get you to 24 V at the AH capacity of each cell (usually 500 or 700 AH). The simplicity and benefit of a series configuration is not to be overlooked. Your installer or electrician can go into more detail.
To conclude this article here is one last diagram inclusive of multiple configurations across 12V, 24V, and 48V.