By removing the negative cable first, you remove the chance for the positive terminal to throw that spark, or arc, because the battery is no longer grounded to the car.
The negative () cable is the ground cable; it is always connected to the frame or body metal and can safely be disconnected first with no chance of causing sparks. By the same token, always reconnect the positive cable before connecting the negative cable.
A car battery will self-discharge at a rate of 5-15% per month with the negative terminal disconnected. However, the alternative option of leaving the battery connected while it isn't being used will drain at close to 20% per week.
Connecting the negative terminal first can create a short circuit, potentially damaging the battery, and electrical system, or even causing injury. By connecting the positive terminal first and then the negative, you can minimize the risk of any accidents or damage, ensuring a safe and successful installation.
Technically, nothing will happen if you disconnect the positive terminal of your car battery first. However, if you short it out, a lot will happen. Depending on what you short the battery with, you might see sparks, be burned by conductive material, or even experience a battery explosion.
“Positive first, then negative. When disconnecting the cables from the old battery, disconnect the negative first, then the positive. Connect the new battery in the reverse order, positive then negative.”
Disconnect your battery terminals before leaving – this prevents your battery from losing charge. Remember, you just need to disconnect the negative terminal.
Removal of Old Battery
Remove the negative (-) terminal first. This precaution is necessary to avoid damage to wiring and the battery by accidentally grounding tools. Remove the positive (+) terminal.
You should never attempt to disconnect your car's battery while your car is powered on. We'd also recommend using safety equipment, like gloves and safety goggles, if you have them on hand.
A battery will not give you any shocks. But however, a short circuit can occur. Remember: in a battery, electricity flows from the negative end to the positive end. If the positive and negative ends of a battery come into direct contact with each other, a short circuit occurs.
Attach the red jumper cables first. Start by clamping one red cable to the positive side of the battery that won't start. Then attach the other red clamp to the positive side of the working battery. Next, clamp one black cable to the negative side of the working battery.
When stored properly out of the car in a secure place, a detached car battery has the chance to last up to six months. Just like any other car battery, it will need charging, but not as often as if it were attached. Giving the battery a charge around every 12 weeks is a good rule of thumb.
Some cars will get up to five or six years out of their battery, while others will need a new one after only two years. In general, your car will usually need a new battery after three to four years. Replacing your car battery is another part of routine maintenance.
But what happens if you've not been driving for a month, two, or more? Most likely, your battery becomes flat or dead.
Disconnecting or replacing a battery on a computer-equipped vehicle may cause starting, driveability and a number of other problems, including loss of air conditioning, power accessory functions (door windows, seats, sunroof), false warning lights, even damage to certain electronic modules!
Consider disconnecting the battery. Another option is to unplug the negative terminal on your car's battery. This will prevent parasitic drain as accessories like your car's clock will still use the battery even when the car is turned off.
If you can't access the negative terminal on the dead car, it's not a problem. In fact, when jump starting a vehicle, experts recommend connecting the negative clamp to a metal ground instead of the negative terminal of the dead battery. Use an unpainted metal part of the engine block.
Run the car for 20 to 30 minutes to charge the new battery
In addition to charging the battery, this gives your car's electronic control module (ECU) a chance to detect any errors.
Be careful not to let the wrench touch both the negative and positive terminals simultaneously, as it could create a spark, cause the battery to short out, or even damage the engine's computer or the vehicle's electrical system.
However for safety reasons it does matter. The whole body of the car is usually connected to the minus pole. And you can accidentally hit that body with the positive lead. So connecting the lead first is safer.
The reason a battery sparks when you connect it is because of the potential difference between the two contact points. In simple terms, if the car has something that is requiring energy before the battery is connected, it will create a larger potential difference, which ultimately leads to a spark.
Although most vehicles come with two battery terminal covers, only the positive battery terminal needs to be covered. Why? Because the positive terminal carries 12 volts and can easily short circuit.