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Stocknazi
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 Posted: Thu Dec 07, 2017 9:15 am Post subject: Battery Cable Resistance Measurment |
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I would like to measure the resistance of me positive battery cable. I have been having some intermittent starting issues.
It's been replaced with thicker wire, so I would like to keep it if possible.
Is there a ballpark number I should be looking for when measuring the resistance of this wire?
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EverettB 
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parker007
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| Posted: Thu Dec 07, 2017 9:58 am Post subject: Re: Battery Cable Resistance Measurment |
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| visual inspection is important, cracked covering, corroded ends loose crimps etc and yes no resistance. |
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Stocknazi
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| Posted: Thu Dec 07, 2017 11:01 am Post subject: Re: Battery Cable Resistance Measurment |
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Just found this information on measuring resistance:
VOLTAGE DROP TEST
A voltage drop test is the only effective way to find excessive resistance in high amperage circuits. It's a quick and easy test that doesn't require any disassembly and will quickly show you whether or not you've got a good connection or a bad one.
To do a voltage drop test, you create a load in the circuit that's being tested. Then you use a digital volt meter (DVM) to measure the voltage drop across the live connection while it is under the load. Voltage always follows the path of least resistance, so if the circuit or connection being tested has too much resistance some of the voltage will flow through the DVM and create a voltage reading.
testing voltage drop with a volt meter
If a connection is good, you should find little or no voltage drop and see less than 0.4 volts for most connections, and ideally less than 0.1 volts. But if you find more than a few tenths of a voltage drop across a connection, it indicates excessive resistance and a need for cleaning or repair.
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"When the people are afraid of the government, that's tyranny. But when the government is afraid of the people, that's liberty."
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Abscate
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| Posted: Thu Dec 07, 2017 11:55 am Post subject: Re: Battery Cable Resistance Measurment |
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| Quote: |
Just found this information on measuring resistance:
VOLTAGE DROP TEST
A voltage drop test is the only effective way to find excessive resistance in high amperage circuits.
>>Well, not the only way. An IR heat imager is a great non-contact way to find excessive resistance in a wire as it will show the power being dissipated as heat.
It's a quick and easy test that doesn't require any disassembly and will quickly show you whether or not you've got a good connection or a bad one.
To do a voltage drop test, you create a load in the circuit that's being tested. Then you use a digital volt meter (DVM) to measure the voltage drop across the live connection while it is under the load.
Voltage always follows the path of least resistance,
>> Hmmm. Voltage doesn't 'flow' it just is. Voltage is like your height above the ground - if you are higher, you will smack the ground harder when you fall.
I think they are trying to say current, but thats not right either. Current flows from a voltage gradient - and the current will divide itself into all paths according to some simple rules, If you have three wires connected between two points of different resistance , all three will have current if the two points are at different voltages.
so if the circuit or connection being tested has too much resistance some of the voltage will flow through the DVM and create a voltage reading.
testing voltage drop with a volt meter
If a connection is good, you should find little or no voltage drop and see less than 0.4 volts for most connections, and ideally less than 0.1 volts. But if you find more than a few tenths of a voltage drop across a connection, it indicates excessive resistance and a need for cleaning or repair.
Well done- thats the crux of the technique for finding excessive resistance.
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Bruce Amacker
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cru62
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| Posted: Thu Dec 07, 2017 1:08 pm Post subject: Re: Battery Cable Resistance Measurment |
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Double check the chassis ground at the front of the transmission. Without good continuity there you will have problems.
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Stocknazi
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| Posted: Thu Dec 07, 2017 2:50 pm Post subject: Re: Battery Cable Resistance Measurment |
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Looks like this will be a 3 person job. One to hold a test lead to the starter, one to hold a test lead to the battery, one to operate the starter.
The diagram shows the test leads attached to the lug battery/starter lugs and not the cable ends. This will test the complete circuit i suppose.
If the test reveals excessive voltage drop, can I isolate the problem further by putting the test leads on the cable ends instead of the lugs to check the cable itself?
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telford dorr
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| Posted: Thu Dec 07, 2017 4:32 pm Post subject: Re: Battery Cable Resistance Measurment |
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Or make up some custom test leads. Get some 16 AWG wire, a pair of banana plugs and a pair of test lead clips from someplace like Fry's. Make up a pair of 6 foot test leads. Clip the wires where they need to go. Have someone operate the starter, and note the voltage reading.
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Bruce Amacker
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chrisflstf
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| Posted: Thu Dec 07, 2017 7:08 pm Post subject: Re: Battery Cable Resistance Measurment |
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Testing can be difficult at times due to dirt, oil and corrosion. You may have to dig a bit with the probe to make a good connection. I usually check stuff 2 or 3 times to make sure Im getting a good reading
Battery cables are cheap also |
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Wayne S. Johnson
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