How can I measure the charge state of a battery?

First of all, it is essential that all batteries are the same (twins) and that they all have the same level of charging. Then it’s important to use in the connection between the batteries, short electric cables, with equal length and with suitable section. Below you will find very simple images to easily understand the connections of the battery terminals.

The parallel connection of two same batteries allows to obtain an output with double capacity than the individual batteries, maintaining the same nominal voltage. Following this example where there are two 12V 200Ah connected in parallel, we will have an output voltage of 12V (volts) and a total capacity of 400Ah (amp hour). The capacity is the maximum amount of charge that can be stored. Bigger the battery’s capacity, greater the amount of charge which can be stored. It is measured in Amperes per hour. In this case means that with a capacity of 400Ah, the battery bank can theoretically provide a current of 400A continues for one hour of time, or 200A for two hours continuously, or 100A for four hours, and so on … Lower the maximum current drawn and longer the lifespan of the batteries.

The series connection of two equal batteries allows to obtain an output twice the rated voltage of individual batteries, maintaining the same capacity. Following this example in which there are two 12V 200Ah connected in series, we will have an output voltage value of 24V (volts) and a capacity of 200 Ah unchanged (Amp hour). In the wind turbines and photovoltaic panels, greater the DC voltage for charging the batteries, and smaller the energy losses along the cables. So for example, a 24V system is better than a 12V system.

Combining the parallel connection with the series connection will be a doubling of the nominal voltage, and capacity. Following this example we will have two blocks from 24V 200Ah joined in parallel, thus forming a total of 24V 400Ah. During the connection is important to pay attention to the polarity, use cables of suitable section and as short as possible. Smaller the length of the connections, lower the resistance that will be formed in the cables to the passage of current and therefore lower the energy loss in it.

In the planning phase of a stand-alone photovoltaic or wind system is essential to have a large and efficient storage system. To ensure proper charging of batteries we recommend high quality and efficiency solar charge controllers. Our wind solar charge controllers are designed to provide the best charging the batteries, ensuring maximum efficiency thanks to innovative MPPT technology. For those who want to transform DC voltage of battery into AC domestic voltage to supply electric devices is enought to buy a sine wave inverter. There are two types: Modified sine wave inverters (suitable for resistive loads, while with capacitive and inductive loads it can generate noise), pure sine wave inverter (suitable for all loads).