The primary disadvantage of constant current charging is that THE CHARGING CURRENT REMAINS AT A STEADY VALUE UNLESS YOU CHANGE IT. A battery charged with too high current rate would overheat and damage the plates, making the battery useless. Do NOT allow the battery temperature to exceed 110 while charging.

CONSTANT VOLTAGE CHARGING. - Constant voltage charging, also known as constant potential charging, is usually done with a motor generator set. The motor drives a generator (similar to a generator on a vehicle); this generator produces current to charge the battery. The voltage in this type of system is usually held constant. With a constant voltage, the charging rate to a low battery will be high. But as the battery approaches full charge, the opposing voltage of the battery goes up so it more strongly opposes the charging current. This opposition to the charging current indicates that a smaller charge is needed. As the battery approaches full charge, the charging voltage decreases. This condition decreases the ability to maintain a charging current to the battery. As a result, the charging current tapers off to a very low value by the time the battery is fully charged. This principle of operation is the same as that of the voltage regulator on a vehicle.

CHARGING PRACTICES. - It is easy to connect the battery to the charger, turn the charging current on, and, after a normal charging period, turn the charging current off and remove the battery. Certain precautions however are necessary both BEFORE and DURING the charging period. These practices are as follows:

1. Clean and inspect the battery thoroughly before placing it on charge. Use a solution of baking soda and water for cleaning; and inspect for cracks or breaks in the container.

CAUTION

Do not permit the soda and water solution to enter the cells. To do so would neutralize the acid within the electrolyte.

2. Connect the battery to the charger. Be sure the battery terminals are connected properly; connect positive post to positive (+) terminal and the negative post to negative (-) terminal. The positive terminals of both battery and charger are marked; those unmarked are negative. The positive post of the battery is, in most cases, slightly larger than the negative post. Ensure all connections are tight.

3. See that the vent holes are clear and open. DO NOT REMOVE BATTERY CARS DURING CHARGING. This prevents acid from spraying onto the top of the battery and keeps dirt out of the cells.

4. Check the electrolyte level before charging begins and during charging. Add distilled water if the level of electrolyte is below the top of the plate.

5. Keep the charging room well ventilated. DO NOT SMOKE NEAR BATTERIES BEING CHARGED. Batteries on charge release hydrogen gas. A small spark may cause an explosion.

6. Take frequent hydrometer readings of each cell and record them. You can expect the specific gravity to rise during the charge. If it does not rise, remove the battery and dispose of it as per local hazardous material disposal instruction.

7. Keep close watch for excessive gassing, especially at the very beginning of the charge when using the constant voltage method. Reduce the charging current if excessive gassing occurs. Some gassing is normal and aids in remixing the electrolyte.

8. Do not remove a battery until it has been completely charged.

Placing New Batteries in Service

New batteries may come to you full of electrolyte and fully charged. In this case, all that is necessary is to install the batteries properly in the piece of equipment. Most batteries shipped to NCF units are received charged and dry.

Charged and dry batteries will retain their state of full charge indefinitely so long as moisture is not allowed to enter the cells. Therefore, batteries should be stored in a dry place. Moisture and air entering the cells will allow the negative plates to oxidize. The oxidation causes the battery to lose its charge.

To activate a dry battery, remove the restrictors from the vents and remove the vent caps. Then fill all the cells to the proper level with electrolyte. The best results are obtained when the temperature of the battery and electrolyte is within the range of 60F to 80F.