Tools used for working on batteries shall be insulated or nonsparking.

6.5.8 STORAGE BATTERIES AND BATTERY BANKS

The following subsection covers rechargeable batteries used as a source of electrical energy. This category is not limited to batteries of a particular voltage and energy rating, since the nature of the associated electrical hazards is similar without regard to battery size; the severity of the hazard increases as the battery ratings increase.

6.5.8.1 TYPES OF HAZARDS

Some of the types of hazards associated with storage batteries and battery banks are listed as follows:

1. Accidental grounding of one polarity of a battery bank can create a hazardous voltage between the ungrounded polarity and ground.

2. Accidental shorting of the exposed terminals or cables of a battery can result in severe electric arcing, causing burns and electric shock to nearby personnel.

3. Hydrogen gas generated during battery charging can create fire, explosion, and toxicity hazards.

4. Exposed terminals in a battery bank present electric shock hazards.

5. Batteries, particularly sealed-cell batteries, can explode if they are shorted or if they are charged at excessively high rates.

6. Electrolytes can be highly corrosive and can produce severe burns to personnel on contact.

6.5.8.2 DESIGN AND CONSTRUCTION CRITERIA

Reliable design and construction criteria for storage areas for batteries are as follows:

1. Battery installations shall conform to the requirements in the current edition of the NEC.

2. Battery banks should not be grounded except as required in NEC Section 250-3; a ground detector should be used to indicate an accidental ground.

3. Batteries should be mounted to allow safe and convenient access for maintenance.

4. Lockable doors should be provided to control access to rooms or enclosures containing battery banks.

5. Approved safety showers and eyewash stations should be provided close to battery banks.

6. Appropriate ventilation for discharges of gas should be provided.

7. In areas where seismic activity is present, the installation should be designed according to local standards.

6.5.8.3 OPERATING CRITERIA

Operating criteria are as follows:

1. Maintain battery bank connections that are clean and tight to prevent excessive heating because of contact resistance.

2. Do not repair battery connections when current is flowing. An accidental opening of the circuit could result in a hazardous arcing condition.

3. Clearly post electrical and other hazards of battery banks and emergency first aid information near the equipment.

4. Arrange the battery banks so that temperature stratification will not result in over- or undercharging.

Note: The optimum storage temperature for maximum battery life is 77F 2 (25C 1).