Unhooking your car’s battery might sound like a simple task, but doing it incorrectly can lead to unexpected issues.
It can damage critical electrical components, trigger warning lights, or even lose the vehicle’s memory settings.
Rather than creating more work for yourself or an auto electrician/mechanic in the future, here’s a step-by-step guide on what you need to know before disconnecting your car’s battery.
1. Know Why You’re Unhooking the Battery
Before grabbing your tools, it’s always best to know precisely why you’re unhooking the battery.
There are several common reasons why you’d want to disconnect your battery, and they include:
- Replacing a dead or weak battery
- Performing electrical system maintenance
- Resetting your vehicle’s electronics
- Preventing battery drain during long-term storage
Understanding the reason helps you prepare for any system resets or precautions necessary for your vehicle.
2. Check Your Vehicle Manual
It’s always important to refer to your vehicle’s manual before performing any work on it. After all, every car is different.
When referring to your owner’s manual, you will want to check for the following:
- What type of battery does your car use?
- Where the battery is located (some are under seats or in the boot)
- Any precautions regarding airbags or security systems
While this is a simple step, it’s vital if you need to troubleshoot an issue later on.
3. Gather the Right Tools and Safety Gear
Regardless of your task, it’s always best to consider safety first and what tools you’ll require to disconnect your vehicle’s battery.
To safely unhook the battery, you’ll need:
- Protective gloves and safety glasses
- A spanner or socket set (usually 10mm for terminal bolts)
- A memory saver device (optional but helpful to preserve radio settings, clock, and ECU memory)
These memory-saving devices are not extremely common, but they can save you time searching for old device codes and resetting preprogrammed electronics.
If your car has start/stop technology or advanced sensors, a battery registration tool might be needed when installing a new battery.
4. Turn Off the Ignition and All Electronics
Before starting, make sure your car is turned off completely.
Remove the key from the ignition, and make sure all electronics (headlights, radio, AC, etc.) are turned off to avoid electrical arcs or memory loss.
5. Identify the Terminals
While we might all assume that your car’s battery is colour coded for red being positive and black being negative, some manufacturers have gone against the grain.
Always look for symbols to identify which battery terminal is which. All lead-acid car batteries have two terminals:
- Positive (+)
- Negative (–)
When confident, unhook the negative terminal first to minimise any chance of short-circuiting.
6. Unhook the Negative Terminal First
As mentioned, always start with the negative terminal first. Using your spanner, loosen the nut on the negative terminal’s clamp.
When loose, carefully lift the cable off the terminal and tuck it safely away where it won’t spring back or touch any metal.
It is essential to know that you shouldn’t let your wrench touch both terminals or metal parts of the car while loosening, as this can cause a short circuit.
7. Unhook the Positive Terminal
To disconnect the positive terminal, you’ll want to repeat the process. Be cautious when removing the positive terminal; unlike the negative side, it is still connected to the electrical system until removed.
Once this is completed, you can remove or replace your vehicle’s battery. Remember that lead-acid batteries are heavy, so you will need both hands to lift them out.
The last step is to reconnect your vehicle’s battery carefully.
8. Reconnect Safely (When Done)
When reinstalling or reconnecting the battery:
- Connect the positive terminal first
- Then reconnect the negative terminal
- Tighten the bolts and secure the battery.
After you’ve reconnected the battery, you should start the engine and check that everything functions as expected.
However, if you’re uncertain about unhooking your car’s battery, you can visit one of our many stockists or your closest Willard Xpress outlet.
