Battery Hazards and its Reasons

There are four main hazards associated with batteries: 

A. Battery acid: The electrolyte in a battery is corrosive and can burn skin or eyes, eat holes in clothing, or even etch a concrete floor. 

B. Flammable gases: Batteries emit hydrogen gas, which is flammable. It ignites easily and can cause a fire or explosion if allowed to accumulate in a small area. 

C. Electrical shock: Many of us are aware of this danger because we may have seen sparks fly when jumper cables are attached to a car battery. 

D. Weight: Batteries, like those used in forklifts, are heavy and require proper material handling equipment to lift them safely. 2. To protect themselves when working with

Safe Operation of Batteries

Because batteries store large amounts of energy, there are certain hazards that are associated with battery operation. These hazards must be fully understood to ensure safe operation of batteries.

Shorted Cell

Cell short circuits can be caused by several conditions, which include the following:

1. Faulty separators
2. Lead particles or other metals forming a circuit between the positive and negative plates
3. Buckling of the plates or
4. Excessive sediments in the bottom of the jar.

The primary cause of some of these occurrences is overcharging and over discharging of the battery, which causes sediment to build up due to flaking of active material and buckling of cell plates.

🔘Overcharging and over discharging of batteries should be avoided at all costs. Short circuits cause a great reduction in battery capacity. With each shorted cell, battery capacity is reduced by a percentage equal to one over the total number of cells.

Gas Generation

A lead-acid battery cannot absorb all the energy from the charging source when the battery is nearing the completion of the charge.

This excess energy dissociates water by way of electrolysis into hydrogen and oxygen. Oxygen is produced by the positive plate, and hydrogen is produced by the negative plate.

This process is known as gassing. Gassing is first noticed when cell voltage reaches 2.30-2.35 volts per cell and increases as the charge progresses.

At full charge, the amount of hydrogen produced is about one cubic foot per cell for each 63 ampere-hours input. If gassing occurs and the gases are allowed to collect, an explosive mixture of hydrogen and oxygen can be readily produced. It is necessary, therefore, to ensure that the area is well ventilated and that it remains free of any open flames or spark-producing equipment.

As long as battery voltage is greater than 2.30 volts per cell, gassing will occur and cannot be prevented entirely. To reduce the amount of gassing, charging voltages above 2.30 volts per cell should be minimized (e.g., 13.8 volts for a 12 volt battery).

Battery Temperature

The operating temperature of a battery should preferably be maintained in the nominal band of 60-80°F. Whenever the battery is charged, the current flowing through the battery will cause heat to be generated by the electrolysis of water.

The current flowing through the battery (I) will also cause heat to be generated (P) during charge and discharge as it passes through the internal resistance (Ri), as illustrated using the formula for power in equation below:

P=I^2 Ri

Higher temperatures will give some additional capacity, but they will eventually reduce the life of the battery. Very high temperatures, 125°F and higher, can actually do damage to the battery and cause early failure.

Low temperatures will lower battery capacity but also prolong battery life under floating (i.e., slightly charging) operation or storage. Extremely low temperatures can freeze the electrolyte, but only if the battery is low in specific gravity.

Conclusion

Battery hazards are summarized below. Battery Hazards Summary Short circuits cause a great reduction in battery capacity.

To prevent short circuits in a battery, overcharging and over discharging should be avoided at all costs. The adverse effect of gassing is that if gassing occurs and the gases are allowed to collect, an explosive mixture of hydrogen and oxygen can be readily produced.

To reduce the amount of gassing, charging voltages above 2.30 volts per cell should be minimized. Whenever the battery is charged, the current flowing through the battery will cause heat to be generated by the electrolysis of water and by I2Ri power generation.

Higher temperatures will give some additional capacity, but they will eventually reduce the life of the battery. Very high temperatures, 125°F and higher, can actually do damage to the battery and cause early failure.

Consequences of high harmonic distortion levels

The total harmonic distortion(THD) is a measurement of the harmonic distortion present in a signal and is defined as the ratio of the sum of the powers of all harmonic components to the power of the fundamental frequency. Distortion factor, a closely related term, is sometimes used as a synonym.

The plant engineer’s worst fear…

Just as high blood pressure can create stress and serious problems in the human body, high levels of harmonic distortion can create stress and resultant problems for the utility’s distribution system and the plant’s distribution system, as well as all of the equipment that is serviced by that distribution system.

The result may be the plant engineer’s worst fear – the shutting down of important plant equipment ranging from a single machine to an entire line or process.

Equipment shutdown can be caused by a number of events. As an example, the higher voltage peaks that are created by harmonic distortion put extra stress on motor and wire insulation, which ultimately can result in insulation breakdown and failure. In addition, harmonics increase rms current, resulting in increased operating temperatures for many pieces of equipment, greatly reducing equipment life.

Table below summarises some of the negative consequences that harmonics can have on typical equipment found in the plant environment.

Negative Consequences of Harmonics on Plant Equipment

While these effects are categorised by problems created by current and voltage harmonics, current and voltage harmonic distortion usually exist together (current harmonic distortion causes voltage harmonic distortion) .

"Harmonic distortion disrupts plants. Of greatest importance is the loss of productivity, throughput, and, possibly, sales"

These occur because of process shutdowns due to the unexpected failure of motors, drives, power supplies, or just the spurious tripping of breakers. Plant engineers realize how costly downtime can be and pride themselves in maintaining low levels of plant downtime. In addition, maintenance and repair budgets can be severely stretched.

For example, every 10°C rise in the operating temperatures of motors or capacitors can cut equipment life by 50%.