Battery connections

john p wrote: »

IM not wanting to get into another discussion on bus bars again but just reposting the post from a long time ago and the results for FARMERJOHNAZ to see if this answers his question..
It shows the very tiny losses you get from using cheap copper tube available from any hardware store.. you just hammer or put in vice the ends of the short lengths of tubing to flatten them then just drill a suitable sized hole each end..

Here is the results of resistance testing and mechanical destruction testing of lugs on copper wires as used in battery interconnects and similar usage.

A total of 10 lengths of copper water pipe was purchased from hardware and plumbing supply stores. The 2 sizes purchased had inside diameters or 1/2 "(12.5mm) and 3/4" (19mm) thickness ranged from 1.25mm to 2mm. All pipe lengths were 10ft (3050mm)

Each size and thickness of pipe was purchased from a different supplier
All measurements were carried out on a calibrated desk multimeter.With a accuracy of+ or - .02%

1.1/2 pipe 1.25mm =.0012 ohms

2.1/2 pipe 1.25mm =.0013 ohms

3.1/2 pipe 2mm soft = .0008

4.1/2 pipe 2mm hard = .0009

5.3/4 pipe 1.5mm = .00065

6.3/4 pipe 1.5mm = .00061

7.3/4 pipe 2mm soft= .00042

8.3/4 pipe 2mm soft = .00041

9.3/4 pipe 2.2 hard = .00040

10.3/4 pipe 2.1 hard = .00039

As noted the resistance was given for 10ft lengths of pipe . If we are going to use any of those pipes as barttery interconnects etc obviously the length used would be about 8" to 10 ", so to get the resistance you would have to divide the above resistance figures by about 12.

To give worst case example the 1/2 pipe 1.25mm at .0013 ohms per 10ft divide by 12 =.0001ohms per foot
THe loss across that pipe used as a battery interconnect would be using 24v connected to a 100 amp load = 40ma
Now lets see how that compares to using a #2 cable and 2 lugs cable resistance = .00052 plus 2 crimped lugs at .00046 total resistance = 99ma loss

Any talk about wondering about losses for 1000 ft of ANY 1/2" copper pipe can clearly be shown to be a pointless exercise. and it way surpasses using #2 cable and the fact is most people would only be using #4 cable as interconnects.With far far greater losses.And as I said in a much earlier post use 3/4 " copper pipe.No matterif it has many impurities its still far far ahead of #0 cable for battery interconnects

Tests involved to measure lug on wire resistance and mechanical strength.
the tests involve #4 cable and closed ring closed tube copper lugs 2mm thick

1.Lug compressed with 500lb pressure on 3 serrated teeth jaws. resistance .00023 ohm.Lug then tested for breakaway

.seperated from cable at 223lbs pull

2,Lug compressed with 500lb pressure on 3 serrated teeth jaws then lug heated and filled with resin cored solder.

resistance .00015 seperated from cable ..failed as cable broke before cable seperated . test pull 325lbs

3. lug and cable resin cored soldered only. resistance .0008 seperated from cable at 127 lbs

As you can see solder only is not good. As a further test the joint melted when a 140a load was connected to the cable and a 12v battery to the lug. Obviously not good.

As you can see I didnt get much work done for employer the day I did all these tests, believe it or not it took 3 of us to do the tests .my work partner to verify the results ..As to do any destructive testing a workplace safety officer has to be present.
Hope some of this helps people understand a little more about cables lugs copper pipes..