Stupid question about battery ground.

[basalt51]

Should everything on my XJ still work if I disconnect the (-) battery cable? If not I guess I have a short or something somewhere? If so whats the point of disconnecting it?

Thanks

 

[Lawn Cher']

Anything electrical should not work with the ground disconnected... the circuits would be open, or incomplete. The electrons would have nowhere to flow to, so you'd have no power.

 

[basalt51]

Well it does all work, and I know there is a large wire connected to the clamp on the negative battery cable that looks like it is grounded to the passenger side fender. So when the negative battery cable is disconnected the cable is still grounded to the fender. The only way for me to get all electrical to shutdown on my jeep is to disconnect the (+) terminal.

Sounds like I need to do some re-wiring?

 

[8Mud]

If the negative terminal is off of the battery and there is nothing still hooked up to the negative pole and it still has a ground. Wash your battery with soap and water, battery acid and the salts that vent, settle on your battery conduct electricity, pretty good. Not a bad idea to wash the battery off with a high pressure washer every once in awhile anyway.
If you listen close, you can often here the electricity going to ground through the battery salts, it kind of crackles.
Coolant has about 1/10 the resistance of water. Or in other words it conductes electreicity about 10 times better. Something else to wash off of your battery.

 

[dmillion]

"there is a large wire connected to the clamp on the negative battery cable that looks like it is grounded to the passenger side fender."

That's right. The battery negative post connects to both the engine block and the body of the Jeep.

"So when the negative battery cable is disconnected the cable is still grounded to the fender."

Now, this doesn't make sense. When you say the cable is disconnected do you mean just from the engine block? If so, then, yes, the cable to the body will still be connected and you'll still have ground. If you disconnect the clamp from the battery post itself, though, then both the cable to the engine and the one to the body will be disconnected and nothing electrical should work.

 

[basalt51]

If you disconnect the clamp from the battery post itself, though, then both the cable to the engine and the one to the body will be disconnected and nothing electrical should work.

Thats the reason I'm posting. With the cable disconnected from the negative battery terminal, EVERYTHING still works. I can even start the jeep.

The only possiblilty I can think of is that I had the winch connected to the accessory terminals and maybe that was allowing a ground? I'm 99% certain I tried disconnecting everything copletely from the accessory terminals though so that shouldn't really matter.

BTW, I'm using a blue top optima. Wierd. I'm in the process of either rebuilding or replacing my motor so while I got room I want to figure this out. Unfortunately it means I can't test anything anymore so I may just replace the cables and put it back together.

Thanks

 

[dmillion]

"The only possiblilty I can think of is that I had the winch connected to the accessory terminals and maybe that was allowing a ground?"

What accessory terminals are you talking about? The second set of terminals on the battery? That is, the screw-in, side-post terminals on the battery as opposed to the to top-post terminals on the battery? If that's the case then, again, yes, that would provide a ground. Both of the negative terminals--on a battery like an Optima with two sets of positive and negative terminals--must be completely disconnected.

 

[basalt51]

The top screw in type had the winch connected at some point. But I'm pretty sure I disconnected both the + and - fromt he winch and tried it and everything still worked. Well the winch didn't :looney:

 

[RichP]

Boy, I'm confused, what happens when you put the battery behind the couch in your living room and leave the jeep in the driveway ?, If it starts then you need to get a patent lawyer really quick...
I seem to remember back when generators were standard and alternators were first making thier appearance you could remove the battery from one and the engine would still run. But I don't remember whether it was gen's or alts you could do this with...

 

[Osprey413]

There must be something we are missing here. Electricity (DC current) doesn't work if the ground is not connected. It simply isn't possible. He is either not removing every wire from the terminal on the battery, or he has a double battery system that he either doesn't know about or is forgetting to disconnect. The battery sits in a plastic tray, which wont conduct electricity. When you disconnect everything make sure the wires can't come in contact with the terminal on the battery. Could you be laying the wires on the terminal accidentally and not realizing it?

 

[Rev Den]

But I'm pretty sure I disconnected both the + and - fromt he winch

Disconnect the winch cables from the battery. Then run your test. There is NO way for everything to work with the neg. battery cables disconnected from the battery.

Rev

 

[old_man]

I'm and electrical engineer with 30+ years experience and I diagnose this as a severe case of operator head spacing. :rtm:

 

[8Mud]

:worship:

I'm and electrical engineer with 30+ years experience and I diagnose this as a severe case of operator head spacing. :rtm:

 

[Jackhill442]

Maybe you have a capacitor for your stereo system installed somewhere. These things hold electricity and allow for a short spurt of electrical operation with the battery disconnected. Otherwise, with only one battery in your jeep, if there is simply not any metal object in contact with any one of the negative terminals, there will never be electrical operation. You are mistaken in your diagnosis somewhere.

 

[jeepguy97]

I thought optima blue tops were marine batteries.

 

[8Mud]

When I was in Dodge truck school, instructors used a pencil, to run a pencil line to ground someplace in the system, usually at a connector. Used to drive the students nuts. :variety: Our last day of school, we drew pencil lines all over the trucks, left a present for the instructors and the next class. :roll:
But in this instance I´m with Old Man, headspace, or a serious cable is still hooked up (guy said it started with the cable off) or our collective leg is being pulled.

 

[cmeuzelaar]

... or he has a double battery system that he either doesn't know about or is forgetting to disconnect.

I'm with Osprey here--do you have an alarm system? Mine had one and there was a backup battery located under the back seat on the driver's side. My strong guess is you have a second battery that you are missing. Again, as others said, make sure you have removed any and all cables from the negative terminal of the main battery--if you still have power to stuff, look for a backup battery for an alarm system, etc.