The room or compartment in which the battery is being charged should be well ventilated. MFD Do not put a battery on charge unless you are wearing safety goggles and a face shield. It must be assumed that explosive mixtures of hydrogen gas are present within the battery cells at all times. Even a battery standing idle generates small quantities of hydrogen due to the self-discharge action. This gas collects in the cells and can be exploded by a torch, match flame, lighted cigarette, sparks from loose connections or metal tools making contact between the terminals and the ungrounded terminal and adjacent metal parts which are grounded.
Since vent cap designs having flame barrier features are not easily distinguished from other style vent caps, it is recommended that vent caps be left on the battery during charging. As a further precaution, place a wet cloth over the battery vent caps. sense flame arresters are used in most modern vent cap designs to reduce the possibility of the battery being exploded by an external spark, this safety feature could be bypassed by removal of the vent caps. Whether such vent caps are present or not, always shield eyes when working around the battery and follow the precautions covered here.
Do not charge a battery unless you are thoroughly familiar with the step-by-step procedure to use. Follow the manufacturers instructions on the charger. If the instructions are no longer legible and you do not have the literature containing the instructions, obtain them from the manufacturer of the charger. Never use a charger without instructions.
Turn the charge rate switch and timer to the OFF position before connecting the leads to the battery. Next, connect the charger leads to the battery terminals, red positive(+) lead to positive terminal and black negative (-) lead to negative terminal. If the battery is in the car, connect the negative lead to the engine block if the car has a negative ground(negative battery terminal is connected to the ground). Connect the positive lead to ground if the car has a positive ground(now rarely occurs). Rock the charger lead clamps to make certain a good connection has been made. Set the electric timer to the desired charging time. Now, turn on the charger and slowly increase the charging rate until the desired ampere value is reached. Do not charge in the red zone. If smoke or dense vapor comes from the battery, shut off the charger and reject the battery. If violent gassing or spewing of electrolyte occurs, reduce or temporarily halt charging.
Never touch the charger leads when the charger is ON. This could break a connection at the battery terminal, creating a spark which could ignite the explosive gases in the battery. Never break a LIVE circuit at the battery terminals for the same reason. Always turn the charger OFF before removing a charger lead from the battery.
When charging or testing a side terminal battery out of a vehicle, always use the side terminal charging and testing posts which have been designed for this purpose.