1. DEFINITIONS
For the purpose of this Code a primary cell or battery is defined as a voltaic cell which, after discharge, cannot be restored to its original (charged) state.
A secondary cell or battery is defined as a voltaic cell which, after discharge, can be brought back to its original (charged) state by passing a current through it in the reverse direction to that of discharge.
2. GENERAL INFORMATION
Secondary cells have different electro-chemical systems which consist of acidic, alkaline, non-aqueous or solid electrolyte. These electro-chemical systems generate different voltages depending on the type of positive and negative electrodes and the type of electrolyte.
During operation some systems may generate and release gasses, which may be hazardous under certain conditions and require specific protective measures.
3. TRANSPORT AND STORAGE
Packing and transportation of secondary batteries is covered in national and international regulations.
The following international regulations for transport, safe packing and carriage of dangerous goods apply:
- Road: European Agreement for the International Carriage of Dangerous Goods by Road (ADR);
- Rail (international): International Convention concerning the carriage of Goods by Rail (CIM) Annex A: International regulations concerning the carriage of dangerous goods by rail (RID);
- Sea: International Maritime Organisation, Dangerous Goods Code; IMDG Code 8 Class 8 corrosive;
- Air: International Air Transport Association (IATA); Dangerous Goods Regulations (latest edition).
For the transportation of lithium cells or batteries refer also to EN 62281 “Safety of primary and secondary lithium cells and batteries during transport”.
For storage of cells or batteries under various climatic conditions, the characteristics regarding charge retention and corrosion effects shall be observed. The manufacturer’s recommendations shall be followed.
4. CHARGING FOR SERVICE
For proper charging of secondary batteries, manufacturer’s specified charging procedures and charging regimes shall be applied. For achieving long service life of secondary batteries the limit values and operating conditions shall be observed.
Normally the charge current for vented batteries is not limited until the gassing voltage is reached. In case of valve-regulated and gastight sealed batteries the manufacturer’s instruction regarding charge current, voltage and temperature shall be observed.
When exceeding the gassing voltage the charge current shall be adjusted according to information from the battery manufacturer or from the relevant safety standards. When applying higher charging voltage, exceeding the gassing voltage, the charging current will increase leading to increased oxygen and hydrogen gas emission, increased water loss, increased temperature and reduced lifetime.
5. INSTALLATION & MAINTENANCE
Care should be taken with all batteries to avoid accidental shorting of their terminals. They should not be subjected to mechanical shock or to extremes of temperature.
In particular 'wet' secondary batteries should be installed upright in a clean, dry, well ventilated place and they should be protected from dust, dirt and accidental shorting of their terminals by metallic objects. If charging facilities are installed as part of the equipment, care should be taken to ensure they are well ventilated to avoid the building up of potentially explosive atmospheres, see STFC SHE Code 20: Controlling explosive and flammable gases and dusts.
Secondary batteries should be kept in a good state of charge in accordance with manufacturers' instructions and given a comprehensive inspection once every six months. They should not be left on charge unsupervised for long periods.
In batteries where the electrolyte is replenishable, the correct level should be maintained; batteries should be topped up with distilled water and care taken to avoid overfilling.
The tops and sides of all batteries should be kept clean and dry and examined for leaks; any vent holes should be kept clear.
When a battery is isolated from its load or any other battery, its bolted connections should be examined for corrosion and tightness. If connections are corroded they should be dismantled, cleaned and greased with petroleum jelly, re-assembled and tightened. Do not use acid neutralising agents and take care when tightening bolted connections to avoid damaging battery terminal pillars.
Remove the vent plug and vent the cell before checking the firmness of the terminal pillars.
Do not attempt to dismantle any battery.
Do not leave exhausted batteries in equipment.
6. SAFETY PRECAUTIONS
Provisions against explosion hazards arising from charging
Gasses can be released during operation (mainly during charging) depending on the type of battery. The gasses can be flammable and can explode at certain gas concentration, temperature and external source of ignition.
Risks can be minimised by adjusted charging procedure, by design, by ventilation of accommodation area and/or prevention of ignition sources. See SHE Code 20 Controlling Explosive and Flammable Gases and Dusts.
The hydrogen concentration should be kept below 1% at all times and the recommended rate of air change is NI x 0.042 cubic metres per hour. (N is the number of cells and I is the gassing current).
Forced ventilation should be provided where natural draught is inadequate. The extract position should be kept as high as possible to ensure thorough scavenging.
In all cases the intake should be at a low level and properly sited to ensure an upward flow round the battery.
All ignition sources should be eliminated as far as is practicable. Smoking and naked flames must be prohibited, static discharges should be avoided and sparks caused by accidental shorting should also be avoided.
Consideration should be given to the provision of electrical equipment which is suitable for flammable gas areas where battery charging is to take place.
Provision against electrolyte hazards
Most of the electrolytes used in batteries are hazardous and can create irritation or burns on eyes and skin. Inhalation and swallowing of electrolyte is dangerous. In case of contact with electrolyte, medical attention is always required.
Properties of electrolyte for topping-up shall comply with IEC 60993 for Ni/Cd. For electrolyte density refer to the manufacturer’s specification.
The preparation of electrolyte solutions for batteries on site should be avoided, where it cannot be avoided contact SHE Group.
Spillage and waste disposal
Sulphuric acid spillages should be cleaned up with materials such as soda ash (sodium hydrogen carbonate) or sodium carbonate (washing soda).
Potassium hydroxide spillages should be diluted with copious amounts of water before mopping up.
Surplus electrolyte must be disposed of as hazardous waste, see site waste disposal contacts.
See SHE Code 31 Controlled and hazardous waste disposal and SHE Code 41 Controlling pollution to air, land and water.
Traction batteries
The enclosure of the battery should be kept clean. Charging and maintenance should be carried out in designated areas in accordance with the manufacturer's instructions or recommendations.
Automatic battery chargers
Automatic battery chargers will prevent over-charging and thus excessive gassing and evaporation. Even so, batteries must not be left unattended for too long whilst on charge.
Battery charging installations
All battery charging installations over 15AH (Ampere hours) should be provided with portable type fire extinguishers suitable for use on acid solutions and electrical fires e.g. CO2. Advise on the number and type of fire extinguishers can be obtained from the site Fire Safety Advisor.
Protective clothing when maintaining batteries
Suggested considerations:
- Protection of eyes and face from splash - acid or alkaline splashes in the eye should be treated by flooding with copious amounts of water. Where mains tap water is not immediately available sterile eye wash bottles and instructions for their use should be placed in each battery room or installation;
- Always obtain medical attention and treatment after first aid;
- Body protection through provision overalls of the boiler suit type or smocks;
- Suitable aprons and gloves of the gauntlet type should be worn. Rubber gloves should be washed after use with soap and water and properly stored; and
- Respirators should be of a type approved by the SHE Group.
7. GENERAL DISPOSAL
Batteries should never be disposed in general waste, see site contacts for battery disposal or employ dedicated battery disposal containers.
8. REFERENCES
- Using Electric Storage Batteries Safely, general information sheet INDG231 (rev1).
- BS EN 50272-1:2010 Safety requirements for secondary batteries and battery installations.
- BS EN 60079-17:2007 Explosive Atmospheres Electrical
- Personal Protective Equipment at Work Regulations 1992, leaflet INDG174.
- BS EN 374, 420 - Industrial Gloves.
