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teddillard
10 July 2011, 0338
Can someone tell me why this is not a good idea? Seems awesome to me… First, take a copper tube with an ID of around .135 (for 12-14awg wire). Drill it like this:

http://evmc2.files.wordpress.com/2011/07/picture-21.png?w=640&h=202

Next, feed the wire through, like this, and crimp and solder:

http://evmc2.files.wordpress.com/2011/07/picture-3.png?w=640&h=236

Slip the whole thing through some heat-shrink and you have a bulletproof, low-profile bus. No?

I want to use this for the balance leads for the Turnigy packs. There are copper tube buses available for huge industrial applications, but I haven't been able to find anything for small gauge wire... seems like it would be a pretty slick way to make up pigtails. Am I missing something?

teddillard
10 July 2011, 0435
V.2.0: with a simple copper pipe hanger:

http://evmc2.files.wordpress.com/2011/07/picture-13.png?w=640&h=418

http://evmc2.files.wordpress.com/2011/07/picture-22.png?w=640&h=412

http://evmc2.files.wordpress.com/2011/07/picture-31.png?w=640&h=413

Not quite as pretty...

teddillard
10 July 2011, 0638
Duh.

These little babies I got from Lowes.

http://evmc2.files.wordpress.com/2011/07/picture-4.png?w=640&h=422

http://evmc2.files.wordpress.com/2011/07/picture-5.png?w=640&h=420

I know Adam's laughing at me. :p

Nuts & Volts
10 July 2011, 0708
What do you need us for Ted :) you're figuring everything out

Only bad thing I see about the copper tube is that it may not be the most electrically conductive alloy of copper. for the balance leads your last idea is definitely the best. For the power leads you just need something a little bit bigger

mpipes
10 July 2011, 0715
Nice and compact much cleaner than stripping more jacket away to twist them all together then solder-bomb! :)

kd8cgo
10 July 2011, 0910
I had a backup electric system I was using a few years ago for power outages and the like, it was just a 12V inverter, couple thousand watt cheapo deal, combined with some group 27 deep cycles. I had used the cheapest battery cables you can buy at auto parts stores, 8 gauge copper wires IIRC. I was getting low voltage cut under heavy load, so I replaced those with some flattened 3/4" rigid copper wall water pipe I had laying around from an old plumbing project with some holes drilled in it and covered with heat shrink, no more LVC on the inverter until the batteries hit a much lower SOC. I might still have those laying around in fact - but it did work very well. I didn't use solder at any point, just mechanical through hole connections. I imagine if your going to try some crimping, the soft walled copper tubing might be better for that.

I also used those copper crimp deals from Lowe's before on an e-bike project to join a leaded Maxi-style fuse holder to some 8 or 10 gauge wire, they seemed to work O.K. for that, never loosened or heated badly, but that was a relatively minor 20-40A load range.

podolefsky
10 July 2011, 0936
Crimp tube is the way to go, at least for small low current wiring. You might use adhesive heat shrink, just because it'll keep it from corroding and makes a better bond (maybe you did? I can't tell).

Not sure this will work for the power wiring. But it might. What gauge are the power cables from the cells?

Tony Coiro
10 July 2011, 1044
(Tony returns from the dead.)

Only issue I see with this is when you go to solder the main power cables, all the solder on the 8 or 10 AWG will go molten as well, potentially making the process fraught with peril but if your crimps are good, it should be legit. I am still deciding how I will do mine but I've got a plus or minus decent idea. My Katana will be alive tonight. Back to work.

frodus
10 July 2011, 1235
why not use copper grounding bar? It's tapped and has screws for everything. They're fairly cheap and they're great for making busses.

http://www.flickr.com/photos/free-stock/5000494972/

teddillard
10 July 2011, 1429
Too big and bulky. Too not permanent (screws vs solder/crimp).

podolefsky
10 July 2011, 1432
non permanent might be nice if you have to replace a cell

teddillard
10 July 2011, 1629
I'm thinking more vibration issues...

podolefsky
10 July 2011, 1633
Lock washers?

DaveAK
10 July 2011, 1635
Screws are used for all kinds of connections in vibration prone conditions. All of Ed's Headway cells for example. And all of my cells and controller connections. There may be other reasons to prefer soldered/crimped over bolted, but vibration doesn't seem like a good one to me. Especially since I can't solder worth a damn. :D

teddillard
10 July 2011, 1707
Sure. If there's no other better option, then screws (with lock washers, or whatever) are fine. But considering the size, simplicity, weight and reliability (not to mention the speed of assembly) I can't see that a screw bus bar is a better solution than those little crimp connectors and some solder. They eliminate the issue entirely.

DaveAK
10 July 2011, 1721
Clearly you've never seen my crimping/soldering! :D

I don't think there's anything wrong with what you propose at all, in fact it looks like an excellent solution. I just don't think there's an issue that needs eliminating.

frodus
10 July 2011, 1932
Thats just a lot of soldering, with heavy gauge wire. Get a good hot solder iron.

And consider that you might have to replace a cell, can it easily be replaced?

I do think a solder or a heavy crimp connection is better than a screw connection. I'm just lazy and a screw is quicker.

podolefsky
10 July 2011, 2252
I think it's fine too, just not easy to take apart. And with all those lipo packs, I'm anticipating having to replace at least one. But hey, it's your project...as long as you leave enough cable, you can always cut a cell out and redo the connection.

If your soldering anything bigger than 8 AWG, or several 10 AWG together, use a torch. Otherwise it'll take you all day.

And don't just solder - if you're worried about vibration, that might be the worst thing you can do. Soldered connections are brittle. Crimp first then solder the crimp.

I realized, if you hadn't already thought of this - four 10 AWG cables equals one 4 AWG. So you could use a 4 AWG crimp tool. Or five 10 AWG equals 3 AWG. Basically x4 in cross-section, go up by 6 AWG, x5 go up by 7.

You could even...probably...I think...use a 4 AWG battery lug with 4 10 AWG cables stuffed in there. Crimp that and you have a bombproof connector.

teddillard
11 July 2011, 0229
Umm, this is for the small balance leads. Haven't got to the power leads yet. But all good points.

Allen_okc
11 July 2011, 0540
why not use copper grounding bar? It's tapped and has screws for everything. They're fairly cheap and they're great for making busses.

http://www.flickr.com/photos/free-stock/5000494972/

you can buy these at Home Depot, fairly inexpensive... i thought about using them simply because if you need to remove or take apart your units, it makes it easier to work on... just my opinion... as the newbie gets slapped upside the head...

frodus
11 July 2011, 0829
Umm, this is for the small balance leads. Haven't got to the power leads yet. But all good points.

oh, didn't see that at first.... just the balance leads.

Can you get some proto board and some pins and make a plug in board for them? Super simple.

teddillard
11 July 2011, 0835
True, and how a lot of guys do it, but again, it's big, and stuff can come unplugged, and it's not at all sealed.

I know. I'm a freak. :D

Tony Coiro
11 July 2011, 0922
oh, didn't see that at first.... just the balance leads.

Can you get some proto board and some pins and make a plug in board for them? Super simple.

I thought about this but I'm like Ted *overcomes brief moment of panic* in that I like soldered and sealed. However unlikely it would be, if a balance pin came off, I can't think of any good way to detect it.

frodus
11 July 2011, 0949
wait, they don't carry much current right?

hmmm, are the balance leads like ribbon cable or separated? work blocks your pictures, so I don't see a lot.

teddillard
11 July 2011, 1002
wait, they don't carry much current right?

right.


hmmm, are the balance leads like ribbon cable or separated?

they're separated.


work blocks your pictures, so I don't see a lot.

that essplains a lot.

:D

teddillard
11 July 2011, 1011
All the alternate solutions aside, though, I'd still love to know why this tube bus idea isn't something everybody uses. Seems like a really good solution, where you do actually need a bus.

Tony Coiro
11 July 2011, 1022
The only issue I could see is the balance leads are 24AWG which would make for a pretty tough crimp job, solder should be fine. You planning this for power leads too?

teddillard
11 July 2011, 1037
... the balance leads are 24AWG ...

Alrighty then. That answers that question. (My batts are still on BO.)


You planning this for power leads too?

No. Haven't got to that point yet, but I might if you were to tell me the gauge of the power leads. :D

Nuts & Volts
11 July 2011, 1103
Alrighty then. That answers that question. (My batts are still on BO.)



No. Haven't got to that point yet, but I might if you were to tell me the gauge of the power leads. :D

20C and 25C packs have 12AWG i believe. Make sure that the copper tube has a large enough cross sectional area at the places between the leads (ie not crimped) to handle the current

teddillard
11 July 2011, 1132
Good point. The industrial strength (for substation use) ones are quite thick... wish I could find that page again.

edit. here: http://www.stormcopper.com/CopperTubing.htm

http://www.stormcopper.com/storm_copper.bus-tube.jpg

Allen_okc
11 July 2011, 1134
this is a connector set up that Kim used on his bicycle - i thought its a pretty clean set up...

__Tango
11 July 2011, 1200
Ted, why a tube? In your original couple of posts, i can't see why you'd need a tube over the flat copper with holes?

teddillard
11 July 2011, 1218
Ted, why a tube? In your original couple of posts, i can't see why you'd need a tube over the flat copper with holes?

um. cause... um ummmm. cause... i like it? yeah, that's it... no, wait. cause it's cool lookin? well, it's small and compact, right? like basically the same diameter of the wire with the insulation. ummmmm. oh crap.

__Tango
11 July 2011, 1222
um. cause... um ummmm. cause... i like it? yeah, that's it... no, wait. cause it's cool lookin? well, it's small and compact, right? like basically the same diameter of the wire with the insulation. ummmmm. oh crap.

Heh. it just seems that your second post with the copper hangers seems simpler and easier to solder (since you can get at the back side. I like it though. :)

Allen_okc
12 July 2011, 0702
i just like the thinking outside of the box, there is always room for improvement - i think thats what Ted was trying to say?