Batteries are a common feature in most types of PV systems that are not connected to the utility grid. Batteries has following functions:

Storage. Batteries store energy being produced by a given generating source, and when this source is unavailable this energy can be be used by the load. The inclusion of storage in any energy generating system will increase the availability of the energy.

Start-up current. Batteries can provide higher currents to the load than the array alone can provide. This is especially useful if a particular load has a high current draw on start-up. Many motors initially have a high current requirement.

Power conditioning.Batteries can function as power conditioning. Two cases where this feature is used is in directly coupled systems, such as water pumping, and in uninteruptable power supplies.

In addition to the different mode of operation, batteries in photovoltaic systems also must bee several other criteria. As reliability and low maintenance are desirable in photovoltaic systems, the batteries must also have a long lifetime. Further, since batteries will often be a substantial fraction of the total cost of a PV system, cost is a significant factor in batteries for PV systems. In general, batteries manufactured for other applications are not well suited to photovoltaic energy applications. The key characteristics of a battery in a renewable energy system are:

How battery capacity and lifetime is affected by deep cycling and extended states of low charge;

the intial and ongoing battery costs; and the maintenance requirements of the battery. In practice, several affects in a battery further alter the performance and operating conditions of the battery, including the presence of additional chemical reactions (which causes battery gassing, corrosion of the electrodes and self-discharge), and changes in the shape of configuration of the electrodes and electrolyte (which may cause shedding or sulfation of the battery (in lead acid batteries), or stratification of the electrolyte. (electrode changes – also caused by solubility in the electrolyte).

Batteries come in multiple varieties. The differences go beyond primary and secondary batteries. The type of battery you use to power your electric toothbrush is very different from the battery you use to power your laptop. Knowing the differences in batteries is helpful and necessary. For example, it is important to know what an alkaline battery is so that you dispose of it properly. It’s also helpful to know about the different types of batteries so that you use them for the right things.

Primary batteries are only supposed to be used once and then thrown away. A primary battery cannot be recharged. They are often used when the battery will sit unused for long periods of time, because they can be made to self-discharge very slowly. This is useful for things like smoke detectors, flashlights, and so on.

Secondary Batteries are designed so that the transformation from chemical energy to electrical energy can be reversed after the battery has discharged. Secondary batteries can be recharged multiple times, but eventually they will stop working altogether. The constant recharging causes wear and tear on the battery that overcomes it after multiple recharges. Secondary batteries are often used for car batteries, laptop computer batteries, MP3 Players and so on.

Alkaline batteries are the most common type of battery and the most commonly used. It is a primary battery type that relies on the chemical reaction between manganese dioxide and zinc. Alkaline batteries can be specially made to be rechargeable. Rechargeable alkaline batteries are usually used in MP3 players, digital cameras, video game controllers, and so on.

Lithium batteries are primary batteries that cannot be recharged. They have a very long life because of their high charge density, but they also cost more than alkaline batteries. They are often used in pacemakers and other critical devices that require a long battery life. Lithium Ion batteries are rechargeable lithium batteries. They are very popular for use in portable electronics because of their long battery life. They do not run out of charge as fast as alkaline batteries.

Solar energy is a form of alternative energy that can be used to power your home. Solar energy, as it is generally conceptualized, is energy directly stored from the sun's rays. A traditional solar energy system requires several components, including solar panels to collect the energy, a charge controller to prevent overcharging of batteries, a power inverter to transform the energy into usable power, and batteries to store the power. Connecting your solar energy system to batteries allows you to store the collected solar energy for use when the sun is not out.

There are some Instructions

1.Designate half of your 2/0 gauge power wires for positive connections and half for negative connections. The easiest method is to wrap red tape around the wire that will carry a positive charge.

2.Connect the unmarked 2/0-gauge wire to the negative output on your charge controller. Connect the 2/0-gauge wire marked with red tape to the positive output on your charge controller. Connect the opposite end of each wire to the respective positive or negative terminals on two different batteries. That is, connect the unmarked 2/0-gauge wire to the negative input on one 12-Volt battery, and connect the marked 2/0 gauge wire to the positive input on a separate battery.

3.Connect the two batteries to the open terminals on each battery with a separate piece of unmarked 2/0-gauge wire. That is, connect one end of the wire to the positive terminal on the first battery, and the other end to the negative terminal on the second battery. Repeat these steps to create a series of parallel batteries that boosts the power and voltage of your solar collection system.