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Old 17-06-2018, 08:13   #31
Zil
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Re: Battery switch & neg bus bar sizing

The negative return and positive feed cables do not have to be the same length for any given device. They do have to be the same gauge. Interconnecting positive battery cables must be the same length and gauge. The same for interconnecting negative battery cables. Negatives do not have to be the same length as positives.
When faced with a choice, it is always better to go with the higher ampere rated connections, fuse, bus, or cable, to reduce voltage drop in dc circuits. Especially critical devices.
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Old 17-06-2018, 09:46   #32
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Re: Battery switch & neg bus bar sizing

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Originally Posted by Zil View Post
The negative return and positive feed cables do not have to be the same length for any given device. They do have to be the same gauge. Interconnecting positive battery cables must be the same length and gauge. The same for interconnecting negative battery cables. Negatives do not have to be the same length as positives.
When faced with a choice, it is always better to go with the higher ampere rated connections, fuse, bus, or cable, to reduce voltage drop in dc circuits. Especially critical devices.

In practice, if the gauge of any cable is directly related to the length of the cable for any given amp current. So you might get in to a situation where a higher gauge is necessary for a given run, negative or positive.


And I think best practice is to have a high current terminal block for most negatives with a connection to the engine in any case. And it is best to have a separate negative to the alternator so the alternator current is not driven through the engine, especially for high output alternators. And I prefer the engine negative at the starter rather than on a distant place so that starter load is not going through the engine as a whole either.
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Old 17-06-2018, 17:00   #33
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Re: Battery switch & neg bus bar sizing

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Originally Posted by Tasso View Post
For high current junctions (eg starter, inverter) I use dedicated wiring as the voltage drop in wires will otherwise cause a slight float in ground voltage. These connections should not touch neg bus bar; use a separate cable for house wiring neg (to bus bar). <snip>

What do you mean by "float in ground voltage"?


I've thought of voltage float as where two negative conductors are not electrically connected, therefore there is a voltage float......
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