What is the correct way to disconnect a car battery? and then the correct way to connect it back?

Undo the negative first and reconnect the negative last.

How To Disconnect Car Battery

Step 1:

With the engine off, pop the hood and find the battery. Detach the negative (black) battery cable from the battery. First loosen the nut with a combination wrench and then twist and pull up on the end of the cable with your hand. You may need to pry up the cable end with a screwdriver if it sticks.

Step 2:

Detach the positive (red) battery cable from the battery using the same method.

Step 3:

Using a combination wrench or a socket and ratchet, remove the battery hold-down clamp.

Step 4:

Take the battery out of the battery tray. Batteries are heavy, so grab from the bottom using both hands.

Step 5:

Use water and a wire brush to clean any corrosion from the battery tray and the hold-down clamp.

Step 6:

Clean the battery cable connectors with a wire brush. To remove heavy corrosion from the connectors, use battery-cleaning solution (available at any auto-parts store).

Step 7:

Place the new battery in the battery hold-down tray and secure the battery with the hold-down clamp. Attach and tighten the positive battery cable. Attach and tighten the negative battery cable. Spray both terminal ends with anti-corrosion solution (optional). Check that all cable connectors are tight. If you can move them at all, your car may not start.

Make sure all loads in vehicle are turned off, key is in the off position. Disconnect the negative battery terminal first then the positive terminal. When installing the new battery connect the positive terminal make sure not ground out the tool your using while tightening the positive terminal. Next attach the negative terminal. Start vehicle and check voltage from the alternator to the battery, to make sure you are receiving full voltage most cars 13.2 to 14.9 volts at idle is good. It's always a good ideal to coat the terminals with a sealer to prevent corrosion, after that you should be good to go.

Manufacturers suggest that you remove the negative side first, and then disconnect the positive side.

Reason being, if you use a larger / longer wrench in the battery compartment than there is space, while disconnecting the positive side, and you touch the wrench to the body, you’ll short out the battery and possibly have it overheat and ****BAMB**** explode.

By disconnecting the negative side first, if you touch the wrench to the body, nothing will happen!

Reinstall the opposite way, install the positive first then the negative side.

Hope this makes sense to you!

Negative off first, on last. Just be sure to isolate the negative terminal after you take it off so it doesn't touch any other metal. You can do this by wrapping the terminal in a cloth or something similar. Current flows from negative to positive and taking the positive off first is very dangerous. But, you would want to put it back on first so that when the negative is put back on, the circuit is completed.

I always forget which cable to remove first and found out the hard way earlier today. while I was removing the positive cable first my wrench struck the metal frame of the vehicle and BOOM! sparks went every where I was lucky to not have gotten shocked. Negative cable off first!

your remove the negative side first.

the reason is this. if you hit the body or any metal part of the car when removing the cable it will not short out.

but if you have not done this and remove the pos. cable, you could short out your battery

Disconnect the negative terminal first and reconnect the positive terminal first.

its negative off first then that way if you touch the hot wire with a tool or ground out the positive on the body there wont be any sparks ......... then to replace it justs like doing a jump start Positive first then Ground

if you take the pos off and touch any metal with your spanner at the same time you will get sore eyes and burnt hands.

ALWAYS take the neg off and tuck it away from the batt terminal at all times (unless the car is really old and has reversed polarity, but i mean really old) DONT TAKE POS OFF FIRST, and reconnect neg last, obviously