Before we delve into the details of how to charge a lead-acid battery safely, we start with two precautions. In the first instance, we assume your charger and battery are in tip-top condition. Never attempt to use either of these pieces of high voltage equipment if you have any reason to doubt them.
Then secondly, if your battery is completely flat, and if you have a smart charger, the rules for how to charge a lead-acid battery may have changed. You see, some smart chargers will not work unless they detect a slight charge.
This is a safety precaution to make sure the electrodes have not shorted. Please consult the manufacturer’s manual for advice.
Precautions to Follow Prior to Charging
Remove any personal jewelry, and put on safety goggles. Disconnect the battery per this post, and remove it to a well-ventilated space in a smoke free zone. Place the battery and the charger on a suitable surface at a comfortable height, and within reach of mains electricity. If your battery has removable caps, top up the electrolyte if required, and replace the caps. Place a wet cloth over them for safety, in case they do not have functional faraday flame guards. You may remove your safety goggles.
How to Charge a Lead-Acid Battery in Detail
Confirm the voltage of the battery by inspecting the label, and re-read the charger instructions before adjusting the output switch accordingly. Identify which battery post is negative, and mark it by placing a piece of masking tape nearby.
Do not attach any cables to the charger or battery yet. After rechecking everything carefully, put on safety goggles again and attach the negative charger cable to the negative battery post.
Rock the charging clip backward and forward to break through any insulating oxidization / corrosion. Repeat the process with the positive charger cable. Next, connect the positive cable to the battery charger outlet. Finally, connect the negative cable to the charger, remembering to face away from the battery just in case there is a spark.
Follow the instructions from the charger provider regarding how to charge a lead acid battery once the connections are complete. We end this post here. There are too many different chargers on the market to continue.