Battery types
Batteries can be classified either according to how they are built or according to the area of use they are designed for.

Construction

Open or Wet batteries
This is the original battery construction. This type requires repeated maintenance because hydrogen and oxygen are emitted from the battery when overcharging. When these two gasses are mixed an explosive gas is formed. Charging should take place in well ventilated areas. The fluid must be checked and refilled when the level sinks to compensate for the gassing. What is not readily noticeable is the corrosion of the electrodes. Over or undercharging will reduce the life of the battery.

Valve regulated batteries
In valve regulated, or recombination batteries as they are sometimes called, the gas generated at charging is recombined into water. This is done through channeling the gas back to the negative electrode, where it is recombined into water before it can escape from the battery. This means that no maintenance is necessary. At uncontrolled overcharging a safety valve will open and let the gas out. Even if it should be a small amount of gas and the risk of explosion is small, the battery will still be damaged since it is not possible to replenish the electrolyte.

Gel batteries
These types of batteries have their electrolyte gelled or absorbed in the separators. Otherwise they are a special type of valve regulated batteries with the same pros and cons. Normally no problems will arise if charged using a high quality charger with voltage regulation.

Area of Use

Stationary batteries
Stationary batteries are used drawing low and often intermittent current during extended periods of time eg as emergency power, emergency lights and warning devices. The number of cycles (complete charging – discharging) are often low. They are on permanent maintenance charging and must be designed for low corrosion of the electrodes.

Starter batteries
Starter batteries must be able to give a high current for a short time without dropping too much in voltage. They must manage a great number of shallow discharges but not so many complete cycles. To be able to give a high current for a short time the starter battery must be designed with a low internal resistance. This is achieved through a large electrode area, and short distance between the electrode plates together with substantial cell connections. Used as the name implies to start engines.

Traction batteries
Traction batteries are made for a low current draw, in comparison to the capacity of the battery, during a long time and to a high level of discharge. They must also manage a large number of cycles. To achieve this traction batteries have thick electrodes and an abundance of active material. Traction batteries are used for forklift trucks and other battery driven vehicles.

Leisure batteries
Leisure batteries are designed as something in between traction and starter batteries. Most of the time they are used with a low current draw and a high level of discharge during many cycles but must also be fit for use as a starter battery. Usage eg. in caravans and leisure boats.

Battery Connections

Parallel connection
When connecting the batteries in parallel the positive poles are connected to each other as are the negative poles. The voltage does not change and the capacity (Ah) will be the sum of the connected batteries.

Series connection
When connecting the batteries in series the positive pole of one battery is connected to the negative pole of another battery. The voltage will be the sum of the connected batteries voltage and the capacity (Ah) will remain the same.

Parallel - Series connection
Both types of connections are used. The parallel connection will raise the capacity (Ah) while the series connection will raise the voltage.

Charging Technique

Battery charging - a science in itself

Now that battery powered equipment is using less ands less energy, it is viable to use batteries to give independence form mains supplies. However, to take the maximum advantage of this independence, the battery charger is of vital importance. Modern switch mode power supplies, such as are used in modern computer, when coupled with charging control logic, offer the ideal characteristics to charge batteries quickly, safely and efficiently to 100%.

A conventional low cost charger using a transformer and rectifier has many disadvantages. The chargers are big and heavy emits large quantities of heat. Many also make disturbing humming noise. At low input voltages they still work but greatly reduced effect. In a transformer, the difference between input and output voltages is determined by the windings ratio. A change in input voltage automatically changes the output voltage. In addition transformers are sensitive to variations in he frequency and waveform of supply voltage.

Many manufacturers of transformer chargers state in their leaflets and specifications a range of input voltages. However, often there is no specification for the performance of the charger at less than the full input voltage. Make sure you obtain this information.

When charging a battery, it is important that the output from the charger is 100% controlled. If the input voltage to a conventional battery charger is reduced by 10%, the resulting reduction in output voltage will substantially decrease the charging. The battery will not become more than 50% full. A 205 reduction of input voltage will results in practically no charging at all. Primary switching technique is not effected by variations in frequency or shape of the input power. It can also be designed to compensate for large input voltage variations. The result is considerably better and more efficient charging of the batteries due to the ability to control the charging cycle and thus always deliver correct charging voltage irrespective of variations in input voltage, frequency and waveform.