Safe to disconnect battery contacts by yourself?

[fleshconsumed]

Had a small issue with my car two days ago which I think may be linked to poor battery contacts that are covered in salt. On Sunday nothing electrical would work, not even headlights. We tightened negative contact on the battery that was a little loose and gave it a boost from the charger just in case and now it works again. Since then I took off negative contact and cleaned it with metallic brush. I'm wondering if it's safe to disconnect positive contact to clean it as well. Yes, I know, stupid question, it shouldn't matter since I already broke the circuit by disconnecting negative contact and everything turned out fine. But I still want to double check before I do the same thing with the positive one. The car is Nissan Altima 05.

 

[Demon-Xanth]

Disconnect the negative, then the positive.

 

[Vette73]

Just don;t cross the streams and you're not gay.

 

[PottedMeat]

do you have to write down security codes?

 

[fleshconsumed]

Disconnect the negative, then the positive.

I can do that. Out of curiousity, any particular reason why I need to disconnect negative before disconnecting positive?

do you have to write down security codes?

I don't know because I don't have manual to the car. I've already disconnected negative wire for cleaning, and everything is fine, radio still works except I had to re-input my favorite radio stations again.

 

[Demon-Xanth]

I can do that. Out of curiousity, any particular reason why I need to disconnect negative before disconnecting positive?

The negative is connected to ground (unless you have an older British car). So if you hit the body with the wrench, no sparks. Once the negative is disconnected, there is no longer a path for current to flow if you hit the body with the wrench while disconnecting the positive.

 

[LTC8K6]

What he said.

If you left the negative terminal connected, you risk a large short circuit...

 

[CRXican]

and when you put it back go positive then negative

 

[Vette73]

and when you put it back go positive then negative

When I taught others i told them the rule Negative first negative last.
Easy to remember, kinda like righty tighty lefty...

 

[DietDrThunder]

It is real fun on older style batteries with the posts on top. I hate it when the 1/2" wrench slips from my fingers and touches both polls.

 

[brblx]

What he said.

If you left the negative terminal connected, you risk a large short circuit...

no. if the postive cable slips and touches the negative or the chassis, nothing is going to happen since the positive side of the battery is not connected.

the only reason for disconnecting/connecting the negative first is supposed to be to reduce the risk of sparks. which is typically a non-issue assuming you have the key (and lights) off (should be very little draw on the batt), and the batt is not overcharged (emitting flammable gases).

yes, it is a good practice to do the negative first/last. but rarely a risk if you do it backwards.

edit- oh, you're talking about dropping the wrench before you get the terminal disconnected. i guess that's valid, but you could just as easily drop it across the batt terminals. don't be a butterfingers.

 

[ShawnD1]

If I remember correctly, the disconnection order had something to do with which side would likely have flammable stuff on it.

battery acid reduction:
H+ acid + electron = hydrogen gas at the negative terminal

Break the circuit at the positive terminal so arcing happens on that side (it shouldn't arc at all if you turned everything off). When you put the battery back in, arcing will happen with whichever is connected last.

 

[LTC8K6]

no. if the postive cable slips and touches the negative or the chassis, nothing is going to happen since the positive side of the battery is not connected.

the only reason for disconnecting/connecting the negative first is supposed to be to reduce the risk of sparks. which is typically a non-issue assuming you have the key (and lights) off (should be very little draw on the batt), and the batt is not overcharged (emitting flammable gases).

yes, it is a good practice to do the negative first/last. but rarely a risk if you do it backwards.

edit- oh, you're talking about dropping the wrench before you get the terminal disconnected. i guess that's valid, but you could just as easily drop it across the batt terminals. don't be a butterfingers.

All the cars I have ever owned have a cover over the positive terminal...so you are really only at risk if you attempt to disconnect the positive first, or attempt to connect the positive last, imo.

 

[spidey07]

Of course always negative first, negative last. The only problems are security on the radio or car ignition. Some modern cars require specific steps to reset the alarm/anti-theft security on the car (they go into a 'theft' state thinking a thief is disconnecting the battery and won't let you start the car). Might want to call a dealer and ask if you need to do any such steps.

 

[Demon-Xanth]

edit- oh, you're talking about dropping the wrench before you get the terminal disconnected. i guess that's valid, but you could just as easily drop it across the batt terminals. don't be a butterfingers.

More common than dropping the wrench is the "yank, no move, yank hard, no move, yank harder, nut suddenly breaks loose and the wrench goes until it hits something" event.

 

[soydios]

If I remember correctly, the disconnection order had something to do with which side would likely have flammable stuff on it.

battery acid reduction:
H+ acid + electron = hydrogen gas at the negative terminal

Break the circuit at the positive terminal so arcing happens on that side (it shouldn't arc at all if you turned everything off). When you put the battery back in, arcing will happen with whichever is connected last.

the cells are arranged side-by-side, so it would be +-+-+-+-+-+- (where + is H+ and - is SO4-)