Working with lead-acid batteries means four separate hazards: sulfuric acid that burns skin and eyes, lead that poisons by dust and fume, hydrogen gas from charging that explodes in air between 4% and 75%, and a short circuit that carries enormous current at low voltage. Add acid to water and never the reverse, keep the top of any charging space ventilated, wash after handling lead, and remove rings and watches before touching a bank.
Part of Battery Building and Maintenance
The four hazards of building and running lead-acid batteries, the protective equipment they call for, and where each is dealt with in detail.
Each Hazard Acts In A Different Way And Needs A Different Control
The carrier lists three hazards: acid, lead and hydrogen. A fourth, the short circuit, appears in its safety remarks elsewhere in the corpus (Energy Storage & Batteries warns that a metal tool across the terminals can weld to them and cause an explosion). They do not overlap: acid burns on contact, lead harms slowly through dust and fume, hydrogen harms in a moment through ignition, and a short harms through current.
The injuries come mostly from the least visible: hydrogen is odourless, colourless and burns with a flame you cannot see in daylight (Gas Hazards). Treat its control, ventilation at the top of the space, as the first rule of any battery room.
What You Need
- Splash goggles — sealed around the eyes; ordinary safety glasses are not enough (Chemical Burns)
- Gloves — nitrile at minimum, neoprene or butyl for concentrated acid; latex does not protect
- An apron or old clothes you can strip quickly
- A respirator for lead dust, with fresh filters (Asbestos, Lead Paint & Other Hazards gives a P100 for lead dust)
- Clean water in quantity, an eyewash bottle, and baking soda for spills (not skin)
- Insulated tools, and a place to hang rings and watches before you start
Method: Before Every Battery Job
Step 1: Take off rings, watches and chains. They bridge terminals.
Step 2: Check the ventilation. The top of the room or box must be open to outside air. No pilot lights, switches or flames near.
Step 3: Put on goggles, gloves and apron, and a respirator if lead dust or fume is possible.
Step 4: Lay out clean water within reach.
Step 5: Work with the charging supply off, and switch it on only when all connections are tight and you are clear.
Step 6: Wash hands and face with soap and water when finished, before eating, drinking or smoking.
If Acid Gets On You
Flood with water for 15 to 20 minutes and do not apply baking soda or any neutralizer to skin, because the neutralization generates heat that adds injury (Spill Response, Chemical Burns). Remove contaminated clothing first. In the eye, hold the lid open and rinse for 20 to 30 minutes without rubbing; all eye exposures need medical evaluation.
Common Mistakes
- Treating hydrogen as a nuisance — it is the hazard that kills and maims
- Working alone — acid in the eyes needs someone else to help flush them
- Neutralizing acid on skin — wash with water instead
- Eating or smoking in the work area — lead goes from hands to mouth
- Keeping the charger switch inside the battery room — the switch spark is a classic ignition source
Safety
Hydrogen from a charging battery explodes, and it collects where you are not looking
Hydrogen is 2 g/mol against about 29 for air, so it rises and collects at the ceiling and in any closed box or lid, and a mixture of 4% to 75% hydrogen in air is explosive. A switch spark, a loose terminal or a pilot light ignites it. Ventilate the highest point of the space, keep switches outside, and never test for gas with a flame (Hydrogen Gas Hazard).
Water poured into strong acid boils and sprays it
Sulfuric acid releases heat violently on dilution, and water added to strong acid floats on it, boils and throws acid out. Always add acid slowly to water, stirring (Acid Handling).
Lead is a cumulative poison with no safe level in this wiki
Lead dust, oxide powder and casting fume are breathed, swallowed and carried home on clothing. Keep children and pregnant people away, and wash before eating (Lead Exposure Prevention).
A battery bank can deliver hundreds of amps into a dropped spanner
The voltage is low, the current is huge, and a metal tool across the terminals welds in place and can rupture a cell. Use insulated tools and take off rings and watches (Terminal and Bus Bar Connections).
What’s Next
- Learn next: Hydrogen Gas Hazard — the hazard that most often injures
- Combine with: Acid Handling — equipment, mixing and spill response in detail