straight forward health and safty advice 
Lead-acid batteries contain dilute sulphuric acid that is poisonous and corrosive, which will cause burns or irritation if it comes into contact with the skin or eyes Battery operated machines normally require recharging after they have been used, but during periods of heavy use they may require a boosting or ‘top-up’ charge. Do not carry out battery charging or 'topping-up' operations unless you are trained how to do it safely.  When charging a battery, follow these precautions: always read and follow the manufactures written instructions; make sure the area has good general ventilation to avoid gases and vapours building up and that the battery charger has a good flow of air through it to cool it; do not smoke or allow sparks near the battery as it gives off gases that can form an explosive mixture; switch off the circuit breaker before connecting or disconnecting the battery, as otherwise a spark can cause an explosion; make sure that connections are secure before switching on. When 'topping-up' a battery, follow these workplace precautions: wear rubber gloves, a plastic apron and a protective face mask; only remove or open vent plugs when specific gravity readings are being taken; 'top-up' battery cells only to the correct level, and as recommended by the manufacturer.
Work precautions