Battery Drain

[Xfaxman]

The safety police say always disconnect the negative cable first, if you don't and the wrench touches metal when any where on the positive circuit, it will draw an arc bigger than most arc welders can produce!

Also checking at the alternator cable won't show a drain any where else.

 

[Soundguy]

Jim, I believe it would work either way. The electrons have to make a circuit for there to be current flow.

Correct, and while it wont matter much on 12v, with higher ac it dc voltages its not a good idea to ever lift groun, or you might find yourself becoming ground path!

 

[Soundguy]

Removing ground first is arc prevention, for our yes we need a closed circuit, not a disadembled one.

The safety police say always disconnect the negative cable first, if you don't and the wrench touches metal when any where on the positive circuit, it will draw an arc bigger than most arc welders can produce!

Also checking at the alternator cable won't show a drain any where else.

 

[Xfaxman]

Removing ground first is arc prevention, for our yes we need a closed circuit, not a disadembled one.

?

An ammeter in series with the disconnected ground cable will show drain current flow anywhere in the positive circuit.

 

[Soundguy]

I'm quite aware how an ammeter in series works.

typical tractor ammeter has number blocks in 10's and a few lines in between. some of these drains might be in the 1 amp range, and would be darn hard to read on a standard gauge ammeter. It it is under 10a, many VOM's have an unfused shunt you can use. or.. the test lamp works.

My post was illustration that I would not lift ground an insert it if it was a higher voltage circuit. lifting ground can make YOU ground.

For arc prevention ground is usually removed first so if your tool strikes chassis it doesn't arc.

If this was a high voltage dc or ac setup.. i'd be making sure i wasn't / couldn't be in the ground path.

?

An ammeter in series with the disconnected ground cable will show drain current flow anywhere in the positive circuit.

 

[Xfaxman]

I should have said what I assumed everyone would know that I meant the ammeter in a multimeter. the one I use has a 10 amp range, then move the test lead to the mA input, where you select one of four ranges, from 200mA, down to 200 micro Amps

I would not trust a test light to show a small parasitic drain.

 

[Tx Jim]

Jim, I believe it would work either way. The electrons have to make a circuit for there to be current flow.

I know voltage drain can be checked by disconnecting either battery cable then inserting test equipment BUT I was taught to always disconnect battery ground cable 1st to eliminate any chance for SPARKS(arcing) by wrench loosening positive cable accidentally touching the vehicle frame.

 

[k0ua]

I know voltage drain can be checked by disconnecting either battery cable then inserting test equipment BUT I was taught to always disconnect battery ground cable 1st to eliminate any chance for SPARKS(arcing) by wrench loosening positive cable accidentally touching the vehicle frame.

OK, I can buy into that as always being good practice. Yes a dead short like a wrench across a battery supply can be a life changing event. A friend of mine took a telephone central office in England down by getting a wrench across the -48 volt battery supply of the Central Office. He described white hot metal near instantly and sagging and falling on to the floor. Also batteries can burst from heat and hydrogen gas production. Not a good thing to have happen.:shocked:

 

[ecbaatz]

OK, I can buy into that as always being good practice. Yes a dead short like a wrench across a battery supply can be a life changing event. A friend of mine took a telephone central office in England down by getting a wrench across the -48 volt battery supply of the Central Office. He described white hot metal near instantly and sagging and falling on to the floor. Also batteries can burst from heat and hydrogen gas production. Not a good thing to have happen.:shocked:

And Oxygen production, as a water molecule is two parts hydrogen to one part oxygen.

Electrician's Mate retired, Submarine Qualified.

 

[k0ua]

And Oxygen production, as a water molecule is two parts hydrogen to one part oxygen.

Electrician's Mate retired, Submarine Qualified.

oxygen, hydrogen, and heat, all the makings for a good bang!