Aluminum busbar?

I was looking up the resistance of metals and aluminum seems to be pretty good for conducting. I have lots of sheets, and need to make bus bars for headway packs.

Is there any reason why I shouldn't use aluminum sheeting? They will be the same size and thickness as the normal headway bus bars. I want to save a few bucks!

It would have less resistance than the nickle plated steel, but copper would be even better.

Common misconception about aluminium here, truth is:
Aluminium is the better conductor in terms of amps per mass (grams)
Copper is more compact, i.e amps per volume (mm³) and has the big advantage that it does not oxidize as easily (better for soldering etc.) - you have to connect somewhere to it...

Edit: and that's why copper is more commonly used - contact/connection resistance, with the possibility to burn down your pack from the heat...

also have a look at the links in http://endless-sphere.com/w/index.php/Ampacity
BTW I use flattened copper tube in my SLI pack

I won't have to solder and connections, headways use screw terminals. Just drill holes in the aluminum. Maybe I'll use a double layer of alum sheet, folded over, then drilled.

veloman said:

I won't have to solder and connections, headways use screw terminals. Just drill holes in the aluminum. Maybe I'll use a double layer of alum sheet, folded over, then drilled.

Click to expand...

Screw terminal is still a connection where corrosion can occur - your call. Check http://endless-sphere.com/forums/viewtopic.php?f=14&t=25846#p377943

If you decide to use it, make sure you use a proper electronic jointing compound like Alinox - I use copper conductors onto aluminium cell terminals (thundersky), and hitting them with a wire brush to burnish, and quickly applying jointing compound ensures no problems in the future.

Aluminum does conduct fine, but the anti corrosion stuff is good advice. The power to your house is very likely aluminum wire btw. Copper from the fuse box on, but aluminum is what's on the electric company poles.

Why add the weight of hunks of copper if you don't have to?

Only real danger from alloy bars was not seeing there condition very easily. While copper soon shows signs of over heating, alloy looks good till it falls away.

Hello!

I use Aluminium Bus Bars that I had laser cut from 0.25 (1/4") T6061 and sent them out for plating.
No "C" rise up to 300amps or so
Be sure that if you source longer bolts (if required), do not put more than 5mm into the cell threads!
I use 16mm bolts with the flat and lock washers. Also, there are times I also add the Headway bus bars
if I still need to shorten my bolt length.

Some people like to take 3/4 copper plumbing pipe and smash it down.
Happy Battery Building to you!

Tommy L sends.....

Check my build thread:

http://endless-sphere.com/forums/viewtopic.php?f=4&t=39480

Cool, thanks for all the advice.

So I did the 1/2" copper pipe method, filed it clean, crushed it flat in a vise, drilled it. I did 6 bars - and spent at least 2 hours. Lesson is: buy the headway busbars for 75 cents each.

I only did 3 but I share the frustration.
I didn't mind back then - had to replace the old lead acid battery on the spot (or queue with the car another day).
Still holding up in daily use.

veloman said:

So I did the 1/2" copper pipe method, filed it clean, crushed it flat in a vise, drilled it. I did 6 bars - and spent at least 2 hours. Lesson is: buy the headway busbars for 75 cents each.

Click to expand...

The headway busbars are apparently plated copper. They are about 1/16" thick which includes the plating, so not much copper in there.
Personally, I like to make sure that when I use energy, that most of it gets to the rear wheel. I do not want to lose energy thru heat in the
bus bar. :wink: Some may argue that it's not much, but when I designed my bus bars, they were for LOW VOLTAGE/HIGH AMPS, so I didn't
want any energy loss.

I learned a lot while figuring it all out. One of my pet peeves is wire sizing. The LOWER the voltage the BIGGER the wire or bar.
Take a look at a car. #4 wire from battery to starter 12v @70amps continuous = 840watts and the wire is fairly short.
In a house, #14 wire 120v @15amps = 1800watts and you can run 60 or more feet with nearly no voltage drop.
Volts is Pressure, and the higher pressure will move the electrons faster so they can produce more work (watts)
If you have Low Pressure, Low Volts, the electrons cant move as fast, a bottle neck affect, and then they just build HEAT in the wire.

So my rule of thumb is, lower voltage BIG wire. Higher voltage Small wire.

On one chart, this was the info:
12v @15 amps 180 watts #14 6 feet max
24v @15 amps 360 watts #14 11 feet max
120 @15 amps 1800 watts #14 wire 68 feet max

So for those running low voltage systems like 24v, they will mostly likely not run more than 11 feet of main pack leads. So #14 wire would be ok
for the 24v 250watt setups.

People running 48v are probably good up to 800-1000 watts continuous with #14 wire, but if they are pulling 4kw from their pack, not good.

I like the higher voltage set ups. I run 84v @ 36amps 3000watts peak in my daily comuter. So #14 wire 1600-2000 watts going thru it? Might just
be big enough, but I run #10 from pack to controller and #8 between packs. The pic below is my A123 132v nominal pack
Each black case is 4S4P 12.8v nominal 9.2ah pack, they are linked in series with #8 wire
I now run 6 cubes 76.8v nom. Below is my 10 cube set up 128v nom 6 cubes with my Grin Ebikes.ca C7225 controller is great for commuting.
Less weight to carry and 33mph/54kph is plenty on a bicycle. It has 700 wh. My commute is 200-300 wh (wind dependent) and I charge at work, so
I use less 50% of the pack. Just how I like it! :wink:

Tommy L sends......

I got some of this copper strap at a garage sale yesterday. It looks perfect to be used as busbar material, already drilled at correct lengths for 38120 headways ( has holes at 2" and 1.5")

Copper plated steel... maybe not as good as pure copper.
https://www.google.com/shopping/pr...a=X&ei=l-XHUdLTCYKI9QSdx4GACg&ved=0CHMQ8wIwAw

veloman said:

I got some of this copper strap at a garage sale yesterday. It looks perfect to be used as busbar material, already drilled at correct lengths for 38120 headways ( has holes at 2" and 1.5")

Copper plated steel... maybe not as good as pure copper.

Click to expand...

That's probably plumbing strap for hanging copper pipe. You can test it under load to see what it does, but I would not expect its resistance to be appropriate for battery interconnects that see dozens of amps.

veloman said:

I was looking up the resistance of metals and aluminum seems to be pretty good for conducting. I have lots of sheets, and need to make bus bars for headway packs.

Is there any reason why I shouldn't use aluminum sheeting? They will be the same size and thickness as the normal headway bus bars. I want to save a few bucks!

Click to expand...

edit
just realised someone already answered most of this....
as to the copper plated steel... like chalo said, test it if you're desperate, but steel is allong way behind alluminium and copper in terms of conductivity. the copper plating is purely there to protect the steel from corrosion.

original message

just use a thicker peice than you would for copper, you'll get the same resistance and less weight.

most people dont realise that most powerlines are alluminium inside. they're a bit thicker to compensate for the higher resistance, but even then they still come out lighter and cheaper than copper.

I dont know however if aluminium oxide has higher resistance... so it might be hard to get a good connection at the transitions between the bussbars and any other part of your wiring/pack. I'm sure someone else 'll chip in on this point though.

go to the sheet metal shop where they make custom gutters or similar stuff and see if they will sell you cooper scraps from the cutoff pile. little strips of copper trimmed off the larger pieces could serve your purpose and maybe not cost too much but at least it would be flat already. you don't need thick. 20-24G would be enuff, imo. you can cut to fit with some tin snips.

Don't use plated steel strap. You will be making have nice little magnets at every series connect!. All kinds of other stuff going on also.

+2 on the pure copper sheet or even cut cu pipe sections.

Thanks for the replies. I'm going to either use the copper pipe and flatten it again, or just buy the busbars for $0.90

Wouldn't dielectric grease help prevent corrosion on the busbars?

Of course it would.
Great advice and knowledge in this thread. If I may add, in years past I was an electrical contractor, even licensed. I mainly installed heavy machinery, no houses, etc. I really only ran across aluminum wire once and was told by someone more knowledgeable than myself that previously, must have been the '60's or so (as this was in the late-'70's) they tried it as a cost cutting measure and it was a miserable failure, even burning structures down due to heating caused by contact resistance oxidation buildup. Also the wires would loosen in the terminals somehow (magically?). I was also told to be sure and use Nolox on the wires when replacing them into the breakers. This was big stuff, like at least 4/0. I only got this word of mouth, but have respect for the source. And he was like _really leery of the stuff. "And then you tighten down them allen bolts with all your might. Check 'em again before you leave that job." Like that. I don't have a code book handy anymore and have forgotten 90%, so not sure whether or not aluminum wire is still allowed. I also have great respect for dogman, but I must say I have not seen it except in that one instance. I rarely messed with service entrance stuff though. Installed HUGE dc motors (40-50hp and even bigger sometimes) and drive controllers mostly.

I also very much agree with Tommy L. I'm all solar here (but not operating due to lack of battery bank and no current need) and have learned that it's better to use much larger wire for things like the solar panel runs than say the code book would call for. Their entire focus is to prevent loss and injury. But in this case, with the low voltages, even though the wires aren't getting warm enough to glow like your toaster they are still wasting too much of your energy as heat, it's being penny-wise and pound-foolish. Make them power transfer wires BIG! The higher your voltages and shorter your runs the less of a factor it becomes though. My solar is 12v and the run from the panels is about 20 feet.
A many year lurker, just signed up the other day mainly because I'll need one of those Big Chicken Motor stickers soon. Sorry to make my 1st post sound like a know-it-all, but thought it might be useful to someone. Mostly I just learn lots from you guys, you are the top notch. Too much good info on ES.
Oh, and I also do the smashed copper pipe thing, quite handy 'cause I always have it around. Only problem sometimes is getting it to contact well with all the abuse.

I have posted a link to a small program in battery faq section to calculate bus bar through output. Best scenario it is 40% less conductive than copper. Here is complete list of aluminium alloy resistivity assuming copper has 100% conductivity.

I got a 5" length of 1/2" copper pipe at Home Depot for $8 today. That's about 24 busbars. It's clean, so no brushing it needed. I should be able to make a better system for knocking these out to cut down on the time.

Tin snips cut it easy. A sharp/ square ground drift punch will cleanly punch through it if you place the pipe on a stud.

I'll probably use a pipe cutter. I don't think my tin snips will cut it doubled (flattened). Or use a hacksaw.