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negative-earth on body v battery
Moderator: -Scott-
negative-earth on body v battery
Im refitting my air compressor into my new truck.
In the diagram it shows that the heavy negative cable needs to run direct to the neg terminal on the battery.
How is that any different to simply earthing out to a solid point on the chassis or body?
Basically the cable wont reach my battery and i want to earth it to another point, neater cabling and less contacts to the battery terminals.
Is there any difference?
In the diagram it shows that the heavy negative cable needs to run direct to the neg terminal on the battery.
How is that any different to simply earthing out to a solid point on the chassis or body?
Basically the cable wont reach my battery and i want to earth it to another point, neater cabling and less contacts to the battery terminals.
Is there any difference?
*there's a rock, drive over it :) there's a bigger rock, drive over it :twisted: there's an even bigger rock, oops broke it :oops: Upgrade broken bit :bad-words:
Goto *
Goto *
By running the earth direct to the battery you eliminate any risk of a dodgy earth between the compressor and body or the body and the battery.
If you careful and make sure there is no paint or corrossion where the cables mount to the body for both the compressor and battery it won't make any difference.
If you careful and make sure there is no paint or corrossion where the cables mount to the body for both the compressor and battery it won't make any difference.
Cheers,
Zuffen
There's no such a thing as too much horsepower
Zuffen
There's no such a thing as too much horsepower
Re: negative-earth on body v battery
Don't just assume that your chassis is earthed - a common setup is battery earth to the body and engine only.thehanko wrote: How is that any different to simply earthing out to a solid point on the chassis or body?
Some chassis appear to be earthed, but have a moderate resistance that causes problems when you draw a couple of amps. The chassis might only be getting earthed via the steering box or something.
Providing your body earth connections are good, you're better off earthing the compressor to the body rather than running a wire back to the battery. The body should have a lower voltage drop over the distance than your average wire.
Also, it eliminates the chance of your compressor becoming the earth path for your starter motor if the earth strap fails. It also prevents ground loops which can cause problems.
simple lesson in dc voltage/current
current (amps) flows from neg to pos ...hence earth is more important than pos
voltage flows from pos to neg ...
you can have a small voltage drop with out effect ..
but a small drop in current will cause you problems ..over heating and resistance in wires fuses and also the unit
current drop in most cases is the reason for failure also a spike or loss of voltage due to resistance relavant to the loss of earth
current (amps) flows from neg to pos ...hence earth is more important than pos
voltage flows from pos to neg ...
you can have a small voltage drop with out effect ..
but a small drop in current will cause you problems ..over heating and resistance in wires fuses and also the unit
current drop in most cases is the reason for failure also a spike or loss of voltage due to resistance relavant to the loss of earth
71 fj40 front shackle reversal +3" , 55 rear springs +3", 35 15.5 claws , 60 diff's 4wheel disc's , SOON TO BE WINDSOR V8 + 5 speed
74 fj40 stock but very clean
84 bj40 3b stock and unloved
74 fj40 stock but very clean
84 bj40 3b stock and unloved
your right but also wrong
electron current flow is from - to +
conventional current flow is from + to -
the current or amps is determined by the voltage source and the resistance on that circuit (ohms law) if the voltage and resistance are stable then current will be stable too. more resistance will lower your current flow.
just make sure all electrical terminations are micky mouse and you wont have a drama
electron current flow is from - to +
conventional current flow is from + to -
the current or amps is determined by the voltage source and the resistance on that circuit (ohms law) if the voltage and resistance are stable then current will be stable too. more resistance will lower your current flow.
just make sure all electrical terminations are micky mouse and you wont have a drama
nissan 98 gu 5" lift 37 creepys, 80%reduction gears, front locker and a gen3 and no money.
On that, depending on what the earth lead is like between the battery and the body, it may need to be upgraded in size. It's size was only ever determined by what was needed to run the vehicle and not any accessories you are going to attach to the vehicle.festy wrote:Also both halves of the circuit are equally important, as together they form a "circuit" - A loss on either side is exactly the same.
If God did not intend for us to eat animals, then why did he make them out of meat?
omg is it still April 1st where you live?MrGrim wrote:simple lesson in dc voltage/current
current (amps) flows from neg to pos ...hence earth is more important than pos
voltage flows from pos to neg ...
you can have a small voltage drop with out effect ..
but a small drop in current will cause you problems ..over heating and resistance in wires fuses and also the unit
current drop in most cases is the reason for failure also a spike or loss of voltage due to resistance relavant to the loss of earth
This is not legal advice.
Depends on precisely how the connection is made.r0ck_m0nkey wrote:On that, depending on what the earth lead is like between the battery and the body, it may need to be upgraded in size. It's size was only ever determined by what was needed to run the vehicle and not any accessories you are going to attach to the vehicle.
If it's designed to carry start current (as some of mine are) then it will be fine to run a bucketload of accessories - which would not normally be running while cranking.
Volts = pressure Amps =flow Ohms (resistance)=the size hole you're trying to push the electricity through. So if the compressor runs at 25 amps and say a dodgy plug drops 2v across it then the dodgy plug heats up at 50watts (25A x 2V). If the dodgy connection was on your starter motor power lead and dropped 2V then the connection heats up at say 200A x 2V so 400watts. Make sense? V=IxR.
Tell me again why punctuation doesn't matter?Shadow wrote:pressure amps
flow ohms
W
T
F
3 cyl wrote:Volts = pressure.
Amps = flow.
Ohms (resistance) = the size hole you're trying to push the electricity through.
So if the compressor runs at 25 amps and say a dodgy plug drops 2v across it then the dodgy plug heats up at 50watts (25A x 2V).
If the dodgy connection was on your starter motor power lead and dropped 2V then the connection heats up at say 200A x 2V so 400watts.
Make sense? V=IxR.
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