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In the previous article we learned about the two main types of batteries used on board – Alkaline and lead-acid. Both these batteries are used extensively on board a ship. So, how to choose between the two batteries for a particular application? In this article we will learn about a few points that need to be kept in mind while selecting a marine battery. Also, we will have a brief look at the operating characteristics of these batteries.
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Marine Battery Selection
Just like for any other devices, the choice between the lead-acid and alkaline battery will depend upon the advantages and disadvantages of each one of them.
For example a lead-acid battery needs fewer cells to reach a particular voltage, however it has a very limited life. Though priced reasonably, it is avoided due to few drawbacks. This type of battery discharges on an open circuit and needs regular attention and charging to keep it going. Moreover, in order to get an uninterrupted and smooth flow, the battery should always be kept in a fully charged condition. The main drawback of the battery is that it becomes useless if left in discharged condition for any period of time.
Contrary to a lead-acid battery, an alkaline battery retains its charge for an open circuit and is not affected if kept for a long period in discharged condition. Moreover, the battery has an ability to retain its charge on an open circuit. But an alkaline battery is comparatively more expensive and needs greater number of cells to produce a particular voltage because of its smaller nominal valve per cell. However, it requires less attention and can go on for hours without continuous charging.
Both batteries, in spite of having certain advantages and disadvantages are widely used at sea for the same basic duties.
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The operating characteristics of a battery depend on the type and capacity of the battery. A battery provides the necessary voltage and current while working in an open circuit by continuously discharging itself. Depending on the capacity, the battery will provide the current and voltage for a long or short duration of time. This capacity is measured in ampere-hour.
Once discharged, the battery is again recharged by providing electrical power. The electrical power is provided according to the capacity of the battery. During this process a bit of energy is lost due to heating of the battery and therefore an additional amount of charge is provided to fully re-charge the battery. However, this energy loss can be prevented by charging with a low current value.
There are three main types of charging methods:
- Constant current
- Constant voltage
- Trickle charge
In constant current, series resistance is reduced to increase the charging voltage. In constant voltage, a high value of current is provided which gradually reduces as the battery charges. The initial current is prevented from getting too high by the circuit resistance. In trickle charging, a very low current is passed to keep the battery continuously in peak condition and fully charged.
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Payne, J.C. (2003) Understanding Boat Batteries and Battery Charging. New York: Sheridan House