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Marine Battery Maintenance & Servicing

Battery are frequently used to provide a low-voltage d.c. supply to certain equipment onboard. To provide these services the appropriate size and type of battery must be used and should be regularly serviced. Two main types of battery are used on board ship: the lead—acid and the alkaline type, together with various circuits and control gear.

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To be available when required batteries must be maintained in a fully charged condition. Where lead—acid batteries are used this can be achieved by a constant trickle charge. Otherwise, for both types of battery, a regular charge-up is necessary.

A measure of the state of charge can be obtained by using a hydrometer. This is a device for measuring the specific gravity of a liquid. A syringe-type hydrometer is shown in Figure above. A sample of electrolyte is taken from each cell in turn and its specific gravity is measured by reading the float level. All specific gravity values for the individual cells in a battery should read much the same.

The specific gravity reading can be related to the state of charge of the battery. The specific gravity reading must be corrected for the temperature of the electrolyte. The value for a fully charged lead-acid battery is 1.280 at 15°C. For an alkaline battery the specific gravity does not alter much during charge and discharge but gradually falls over a long period: when a value of 1.160 is reached it should be replaced.

Syringe type hydrometer
Fig:Syringe type hydrometer

The electrolyte level should be maintained just above the top of the plates. Any liquid loss due to evaporation or chemical action should be replaced with distilled water. Only in an emergency should other water be used. It is not usual to add electrolyte to batteries.

A battery must be kept clean and dry. If dirt deposits build up or spilt electrolyte remains on the casing, stray currents may flow and discharge the battery. Corrosion of the casing could also occur. The battery terminals should be kept clean and smeared with a petroleum jelly. The small vents in the cell caps should be clear at all times.

Cell voltage readings are useful if taken while the battery is discharging. All cells should give about the same voltage reading, This test method is of particular value with alkaline batteries, where specific gravity readings for the electrolyte do not indicate the state of charge.


Related Info:

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  8. Ships battery maintenance guidance
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    11. Good insulation resistance is essential to the correct operation of electrical equipment. A means must be available therefore to measure insulation resistance. Readings taken regularly will give an indication as to when and where corrective action, maintenance, servicing, etc., is required....

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    13. As a very flexible, reliable means of motor speed control the Ward-Leonard system is unmatched.The system is made up of a driving motor which runs at almost constant speed and powers a d.c. generator .....

  13. Danger of electric shock to human body
    14. The resistance of the human body is quite high only when the skin is dry. The danger of electric shock is therefore much greater for persons working in a hot, humid atmosphere since this leads to wetness from body perspiration.....




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