Customers often ask about the best way to disconnect and reconnect a lead acid starter battery. Which cable should they take off first, and which order do they go back? Which lead acid battery safety rules apply? This is an important question, because doing it the wrong way around could cause a spark, and even short out the battery.
The Answer Depends on How the Battery Earths
Most vehicle batteries have negative earths. In other words, their earth wires bolt onto the metal chassis. Thus, if we were to connect the positive terminal to the chassis too, we would have an instant short.
This is not impossible. The spanner we are using to tighten the positive clamp could accidentally touch metal under the hood or trunk.
Lead Acid Battery Safety Rules for Disconnecting
Let’s say we decide to charge a battery from an outside source. We know we must remove it from the vehicle to a well-ventilated space.
First, we make sure we turn off all electric circuits. If we have the entertainment system beating out, this will increase the magnitude of the spark if we accidentally cause a short
Therefore, we disconnect the negative terminal first. The battery is now isolated from the vehicle. Inadvertently contacting the positive terminal and metal cannot cause an electrical discharge. However, if we accidentally drop the spanner across the terminals, or if our necklace touches both that is a different matter.
How to Reconnect Lead Battery Safely
It follows that we should remove all body jewelry before working with lead-acid batteries. Reconnecting batteries is the reverse process. First, we connect the positive cable and tighten it. Then we can connect the negative one without causing a spark. Stay close to us. Our next post will explain more lead acid battery safety rules. Because we want you to have them in mind when charging a battery from an external source.
Preview Image: Loosening Positive Terminal