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Old 04-25-2005, 09:48 PM   #16
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I think braided gives a better contact "patch" on each cell. I think that this is where the difference lies between braided and solid bars. Solid bars also give a good contact patch if it is soldered the right way, by that I mean the bar has to sit very flat on the cell, or else the solid bar may have a contact patch the size of a pin head. Which would result in resistance.
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Old 04-25-2005, 09:52 PM   #17
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Quote:
Originally posted by Soviet
There would be no difference if both the wire tested and the bar contain the exact same amount of metal.

The difference would be that in high-amperage situations, higher than what we see in RC (Aircraft for example), solid connections are preferable to wire. (Or at least super-thick gauge wire).
the purpose for braid being better is the material content is more pure... pure copper is the best material you can use.. people seem to think silve bars work best... break a silver bar in half.. you will notice they are copper on the inside.. the silver is there for looks,, it keeps the bar from tarnishing...pure copper is very soft an pliable... there is a company now making copper bars.. promatch i think./. they are buying copper braid and melting it down to make the purest bars available..

chewck the link.. i started a thread on this subject a while back.. there is alot of info and test info on the thread..

also.. braid will flow more power then a bar...just look at the car stereo industry... 12 batteries in a car, all hooked with massive wire.. the oblect for car audio is efficiency...


http://www.hobbytalk.com/bbs1/showthread.php?t=109451
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Old 04-25-2005, 09:57 PM   #18
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actually your contact path is through the solder. If you look a comercial switch gear (very large breaker panels) they use solid bars instead of wires becuase the resistance is lower and the contact paths are larger. I would think that because as someone mentioned, the braided wire would soak up much of the solder and increase the resistance due to the solder having more resistance than the material is soldered to.
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Old 04-25-2005, 09:59 PM   #19
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Quote:
Originally posted by Pro4Capece
Actually, shoe-goo and glue are not good ideas for building batteries. The cells get hotter. It is harder to make the pack fit in a tight chassis. If you need to dissasemble the pack, the shrink wrap is ruined. When have you ever seen a pro using glue to keep his (or her) cells in-line?


PRO's dont pay for cells... there packs are run a few times then gone... they do not have to worry about care of the cells..

3300 cells like heat... so this cells get to hot talk is bogus...

also disasembly is easy as can be.. the shrink wrap breaks right open when you twist.. so number one.. if you rematch, you dont have to sit and cut off each shrink wraped cell. they do it themselfs on disasembly... and if you get in a bad wreck, you can be sure your pack will make it through.. over 17 years of racing i cant even count how many guys packs turn into a slinky in a big wreck.. good luck making a pack fit well after that...
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Old 04-25-2005, 10:19 PM   #20
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Quote:
actually your contact path is through the solder

using the proper solder is definatley a major thing..
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Old 04-26-2005, 06:37 AM   #21
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Not a Pro or even a high level racer, but what I am is an avid racer. I love and have tried just about every thing out there....
I have used the Acer Braid in question....and have used and am using the Promatch Bars.
They Acer Braid had less resistance Yes.....Problem....You have to use a large amount of solder to get a good solid connection which is very important in battery building...(solder does not have low resistance by the way)
That is why I use the Promatch bars now....I need very little solder to make the crutial connection.
The Shoe Goo debate.....hog wash....That is why you use indiviual shrink wrap in the cells. I would rather have a stable pack than a slinky look-a-like after you get hit...
In fact saw it happen the last race I was at....we had the same debate and this guy who swore that glue was bad....He changed his tone after a big crash..
Just my two pennies...
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Old 04-26-2005, 06:38 AM   #22
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In fact I have some left over Acer Braid if anyone want to buy some cheep. PM me...LOL
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Old 04-26-2005, 07:00 AM   #23
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what do pros use? battery bars instead of braids. this is enough to prove that bars are better than braids, if there actually is any resistance difference.
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Old 04-26-2005, 07:18 AM   #24
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Quote:
Originally posted by billtc3
what do pros use? battery bars instead of braids. this is enough to prove that bars are better than braids, if there actually is any resistance difference.


If you use bars properly and asseble your pack straight and true, with bars that contact flat and you solder with flux, you will have a perfect battery. End of story.
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Old 04-26-2005, 07:38 AM   #25
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None of us are "pro's" and it really isnt something to worry about. You nor they will notice the extreemly small difference in performance. Your all arguing a null point.
Yea braid may flow better but in our aplication and the level at which most people drive you all could be driving Tamiya connectors and it wouldn matter a rats azz!
Using a braid will reqire more solder which in turn will make a heavier pack.
Which would defeat the purpose anyway.
Using a bar is cleaner and lighter. I take a dremel before soldering a bar and grind away the silver so the copper is exposed. So when you apply the solder you have a better mechanical connection and less resistance because the current doesnt have to go thru the silver. And since you scuffed the bar , do the cell also you'll require less solder, cleaner looking, and better flow.

Like I said earlier 98% of us dont need to worry about petty things just practice and get better! Enjoy your toys and stop burnin brain cells on things that dont matter. Wether you jump of the bridge follwing the pro's or not. There is a method behind the madness on why they use bars instead. THey are the worlds best for a reason. I doubt they would use a bar if braids were that much better.
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Old 04-26-2005, 07:50 AM   #26
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Ideally, the bar is suppose to touch the battery with no solder in between. The solder is only to hold the two together along the top and edges (not easy to do). With braid it seems as though the connection is all solder but I like the fact that the braid lets the pack flex a little and takes the stress of the joint.
I've tried both and I'm not good enough to notice any difference.
I'm using bars right now because they look better and are easier to use.
My $0.02
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Old 04-26-2005, 08:13 AM   #27
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Quote:
Originally posted by jag88
Ideally, the bar is suppose to touch the battery with no solder in between.
Surely this isn't right? The solder will give you conductivity at a molecular level - just holding the bar in place against the cell isn't up to the same standard. Obviously you want to keep the amount of solder used to a minimum as solder is not as conductive as copper.

Just out of interest, what dimension copper braid are people using? The most appropriate size I can easily get my hands on the the UK is 6x0.15mm (2mm square), but is only rated for 30A. 63A and 90A ratings are too wide to be practical.
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Old 04-26-2005, 08:33 AM   #28
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could someone please put these materials, in their pure form, in order of greatest to least resistance?

a) copper
b) gold
c) silver
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Old 04-26-2005, 09:01 AM   #29
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Silver
copper
Gold
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Old 04-26-2005, 09:06 AM   #30
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Seaball - Hey, Chris. I've done quite a bit of studying on this subject in recent weeks and the answer is that copper, gold and silver are really very, very close to one another in terms of resistivity.

One source I'll site says the following:

'The resistance characteristic of metals is called resistivity. The resistivity of copper is 1.7 microohm-cm. Silver is very slightly lower, 1.6. Gold is a bit higher, 2.4.'

Most sources you read will explain it this way: gold is generally the most desirable since a) it does not corrode over time and b) it is the most maleable (flexible) of the three allowing it to 'spread' itself over the contact surface.

Silver has the least resistance, *BUT* it does tarnish/oxidize over time. Having said that silver oxide is still very, very conductive, so that's not necessarily bad.

Copper is nearly the same as silver in its resistivity profile, but it tarnishes terribly and the oxide isn't nearly as conductive as silver's. I never use copper bars.

For the past six months, my favorite bar has been the Promatch bar. We'll be selling that on our website in the next few weeks. It has a very large contact patch allowing there to be flush contact between the bar and the cell surface as well as adequate room for a strong solder connection. It's also reasonably priced compared to the gold bars.
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