Charging lead acid batteries

Batteries generate explosive hydrogen gas, even during normal operation, but additional hazards during charging raise the risk to workshop and other personnel.

Batteries generate explosive hydrogen gas, even during normal operation, but additional hazards during charging raise the risk to workshop and other personnel.

In eastern Victoria a worker was injured when a large truck battery exploded whilst he was moving the charger clips.  Moving the battery clips resulted in arc sparks between the clips and battery terminal. The force of the explosion resulted in approximately 4 litres of battery acid spilling or being blown out of the battery and pieces of plastic and a vent over 4 metres from the battery.  The worker was showered with battery acid and cuts to the hands caused by the shattered battery casing.

Causes:

• Two gases are released when batteries are charged. Hydrogen is very flammable and easily ignited while oxygen supports combustion.
• The battery charger was not turned off while moving the clips. The process of moving / removing charger clamps while charger is still turned on is not recommended due to the ignition and explosion risks.  The charger must always be turned off before placing, removing or adjusting the clamps.
• The battery vents were not screwed into place but sitting loosely in their location ports.  Removing the battery vents and/or leaving the battery vents sitting loosely in their ports during charging is inherently unsafe and never recommended.  The vents are designed to Australian Standards to allow the hydrogen and oxygen gasses generated during charging to safely vent to the atmosphere while preventing a flame front from entering the battery in the event of an incident.  They must be properly and securely in place during charging.
• The worker was wearing work clothing and boots but not wearing PPE (goggles or glasses and face shield, chemical gloves, chemical apron or overalls) while performing the battery maintenance task.  The correct PPE that must be worn is clearly stated in the relevant Australian Standards, the battery manufacturer’s instructions and the MSDS’s for flooded cell lead acid batteries and includes chemical goggles or safety glasses and face shield; acid resistant gloves; acid resistant overalls or apron and safety (preferably acid resistant) work boots with protective toe caps.

What you should do:

In a workplace there should be a written procedure for charging batteries and all personnel performing the work should be trained in safe battery maintenance procedures.

Battery charging procedure

• Always read the manufacturer’s instructions before attempting to charge a battery and ensure you have a good quality Australian approved battery charger. The battery type will determine which type of charger is required. Follow the battery charger manufacturer’s instructions.
• Avoid Overcharging Batteries. The non-automatic (manual) battery charger models can overcharge a battery if left connected for an extended period of time, resulting in loss of water and creation of hydrogen gas.
• Always locate charger as far from battery as DC cables permit.
• Check fluid levels in each cell before connecting charger, adding water to each cell until battery acid covers plates to help purge extra gas from cells. DO NOT overfill. For a battery without removable caps (maintenance free battery), carefully follow manufacturer’s instructions on charging. Some sealed maintenance free batteries have a battery condition indicator. A light or bright coloured dot indicates low water. Such a battery needs to be replaced, not charged or jump started.
• Charge in well ventilated area.
• Avoid contact with battery acid.  Battery posts may have acid corrosion. DO NOT get corrosion in your eyes. Avoid touching eyes while working near battery.
• The correct PPE that must be worn as stated in the relevant Australian Standards, the battery manufacturers instructions and the MSDSs.  Correct PPE includes chemical goggles or safety glasses and face shield; acid resistant gloves; acid resistant overalls or apron and safety (preferably acid resistant) work boots with protective toe caps.
• Make sure charger clips make good contact by twisting or rocking them back and forth several times. Always plug charger into an electrical outlet AFTER all connections have been made.
• Always turn the charger off before attaching, rocking, or removing the terminal clamps.
• If necessary to remove battery from vehicle to charge, always turn off all accessories in the vehicle. Then always remove grounded terminal (connected to car frame) from battery first.
• Touching both battery posts or battery post and car metal parts with a tool will cause a short circuit and will spark, be extra cautious when using metal tools on or near batteries.
• Items of jewellery (eg watches, rings etc) must not be worn at anytime by people working on batteries because they may short out the terminals.
• Keep open flames and sparks away from the battery.  Charge batteries away from welding, grinding or other spark producing activities.  No smoking.
• Charge batteries away from flammable materials e.g. spray painting, petroleum products, etc.
• Keep vent caps in place.
• Have acid spill control and neutralising agent readily available such as a 10kg container of bi-carb soda (sodium bicarbonate) available to neutralise acid leaks and spills.
• If battery acid contacts skin or clothing, wash immediately with soap and water. If acid enters eye, immediately flood eye with cold running water for at least fifteen (15) minutes and get medical help immediately.