Re: Amp draw on battery
[Re: wtucker]
#1388998
02/17/13 02:17 PM
02/17/13 02:17 PM
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Joined: Jun 2010
Posts: 92
PA
68_CONV_300
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Posts: 92
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Quote:
What should be the maximum voltage draw be between the negative cable and negative post?
Voltage is a measurement of potential work to be done , there is no draw associated with it.
think voltage as water pressure
think of current(amps) as the volume of water
think of the size of a pipe as the resistance in a circuit
if you have a steady water pressure (volts) and a 1/2" pipe(resistance) there will be a certain flow (amps) rate.
if you increase the pressure (voltage) but keep the pipe (resistance) the same size you will have more flow (amps)
if you keep the pressure(voltage) the same but increase the pipe size (resistance) you will also get more flow (amps)
I think you were asking how many volts should you read between the cable and the post when disconnected. and that question can only be answered by having a resistance reading from the positive cable to the negative cable.
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Re: Amp draw on battery
[Re: wtucker]
#1388999
02/17/13 02:22 PM
02/17/13 02:22 PM
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Joined: Jun 2010
Posts: 92
PA
68_CONV_300
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Posts: 92
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Quote:
I,m reading 12.55 volts between the negative cable and negative post. I assume this is not normal?
this is perfectly normal ,the reason you are getting this reading is because there is a current draw with less resistance than the internal resistance of the meter. what you are creating by doing what you are doing is creating a circuit that is a called a voltage divider, and there is no way I'm going to explain it in a post here.
you need to be concerned with the current draw you are getting with the meter connected in series and in amp reading mode.
your reading of 40 milliamps is normal for a car with any type of electronics or an electric clock in it.
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Re: Amp draw on battery
[Re: Supercuda]
#1389002
02/17/13 03:23 PM
02/17/13 03:23 PM
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Joined: Jan 2003
Posts: 2,252
New York
rarefish
top fuel
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top fuel
Joined: Jan 2003
Posts: 2,252
New York
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Quote:
Quote:
That is more like the voltage you would read across the battery terminals. Even if something is wrong there still should be no voltage reading when you put the meter in series with the cable and terminal.
Wrong, he's reading a normal reading for that. Though you really shouldn't measure voltage that way it is normal.
Now you got me wondering... so I just went out into a very cold garage and popped the hood on my Dakota. I pulled the neg terminal off the battery and put my meter in series and read 12.3 vdc 
Well now I'm surprised. Anyway I also checked curent flow and found that I had .04 ma
I stand corrected on the voltage statement that I made earlier.
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Re: Amp draw on battery
[Re: rarefish]
#1389003
02/17/13 03:36 PM
02/17/13 03:36 PM
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Joined: Nov 2007
Posts: 21,822
Kirkland, Washington
Pacnorthcuda
Too Many Posts
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Too Many Posts
Joined: Nov 2007
Posts: 21,822
Kirkland, Washington
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Quote:
Quote:
Quote:
That is more like the voltage you would read across the battery terminals. Even if something is wrong there still should be no voltage reading when you put the meter in series with the cable and terminal.
Wrong, he's reading a normal reading for that. Though you really shouldn't measure voltage that way it is normal.
Now you got me wondering... so I just went out into a very cold garage and popped the hood on my Dakota. I pulled the neg terminal off the battery and put my meter in series and read 12.3 vdc
Well now I'm surprised. Anyway I also checked curent flow and found that I had .04 ma
I stand corrected on the voltage statement that I made earlier.
Ya might want to put a charger on that battery.
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Re: Amp draw on battery
[Re: rarefish]
#1389005
02/17/13 07:17 PM
02/17/13 07:17 PM
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Joined: Jan 2003
Posts: 27,421
Balt. Md
383man
Too Many Posts
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Posts: 27,421
Balt. Md
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If you unhook the neg or pos cable and put a voltmeter in series with it you will not get an accurate voltage reading. As you said just 40 milliamps had the voltmeter reading 12 volts. Thats because a voltmeter needs to hooked in paralell in a circuit to read right. When you remove a battery cable and hook a voltmeter to the battery post and the cable you are hooking the voltmeter in series which wont read the correct voltage. Many guys used to use test lights in series with a cable but thats not an accurate way either. Thats why you use the ammeter to check the draw as thats the only way to get accurate reading. Ron
Last edited by 383man; 02/17/13 07:18 PM.
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