Debate on wiring risk of positive/negative wires along a path

Question

I came across a design of a battery pack. As you see on the photo, the red wire is positive and black is negative.

The red wire lays across the top of the battery pack and comes to the connector.

One of my classmates said to me that, there is more risk of moving the red wire across the top of the battery pack, and I should move the connector to the left side and draw the Black wire across the top of the battery pack. So this way the risk of the short circuit will be less.

But does it really matter which wire goes across the top of the battery pack as both wires carry a total voltage?

If it is the red or black wire, both wires carry a total voltage of the battery pack. I think it does not matter which wires go across the battery pack. I want to get your opinions regarding this question.

Best Wishes

---------------Solution by Neil_UK in comments-------------

I redrew the battery from the comments and put the photo here.

score 3 · Accepted Answer · answered Oct 28 '20 at 11:37

The danger is that the wire insulation chafes, and shorts through to a cell terminal.

The way the cells are arranged means that all voltages from zero to battery voltage are present at the terminals on the top. This means that whether the black wire or the red wire runs across the top, there is an equal set of voltages between the wire and the cell tops, so no theoretical difference between the two arrangements.

There would be no practical difference between the two arrangements either, as the insulation on the wires would usually be substantial enough to resist chafing.

It should be pointed out that the particular arrangement of cells illustrated requires one of the wires to run the length of the battery. There is an alternative arrangement which results in the two terminals being at the same end, so neither wire has to travel the length of the battery. Numbering the cells from 0 at the negative pole, these two arrangements are

illustrated       alternative
 9 6 5 2 1         5 6 7 8 9 
 8 7 4 3 0         4 3 2 1 0

Thanks. Your solution is the best. This way the output tags are in one side so no need to run the wire on the top. — Habib Anwari, Nov 01 '20 at 13:00

score 0 · Answer 2 · answered Oct 28 '20 at 11:30

These batteries are stacked in series, so whatever wire is the longer would short-circuit to a different voltage, be it red or black.

The battery casing is negative. Thus, if there is a hole in the plastic sheath then any stray wire is more likely to short-circuit to its negative electrode.

There is a minimally-probable scenario in which the long wire detaches from the last battery, curls back and shorts through a hole in the sheath of the first.

More probably, if the wire has significant slack and the short wire detaches, it can be pulled over to short against the last battery. I have actually seen this happen.

But since this is a multi-stack, the polarity has minimal effect on safety. And your wiring run is unspecified.

Best solution would be to keep the cases lower to minimise the voltage shorted, i.e. 0V to the case of the first battery. Then tie the wiring back so it cannot stray far. This is what every technician will expect to see, and that alone makes it the safest.

Inchbal, Thanks for the comment, Yes you are right about the safety of the pack. On comment above Neil_UK provided other solution that requires no lead to go over the pack. And the output can be taken from two tags that are outside of the battery. — Habib Anwari, Oct 30 '20 at 11:34

Debate on wiring risk of positive/negative wires along a path

2 Answers2