cal3thousand
10 MW
So what we need is a low temp solder to be made. Maybe graphene paste in the future?
Matt Gruber said:i tested a spring from a flashlight!
at 2.5A 208 mv drop! (remember my epoxy copper is 6 mv)
at 7 amps 608 mv drop and it burned my finger! (coppery/epoxy 12 mv)
i had this spring lying around because i soldered the wires last year direct to the cell, and put in a real switch and took out the spring. flashlight works perfect ever since. no flickers ever. next flashlight i'll use epoxy.
So sounds like that epoxy is pretty good compared to spring, do you have a URL for it?Matt Gruber said:i tested a spring from a flashlight!
at 2.5A 208 mv drop! (remember my epoxy copper is 6 mv)
at 7 amps 608 mv drop and it burned my finger! (coppery/epoxy 12 mv)
i had this spring lying around because i soldered the wires last year direct to the cell, and put in a real switch and took out the spring. flashlight works perfect ever since. no flickers ever. next flashlight i'll use epoxy.
In that application, hte braid is the current-carrying path, not hte spring, htough. The braid is typically embedded in hte carbon brush's core, and simply fed thru the center of the spring that pushes the brush down onto the commutator. The other end of the braid is often bradded/riveted to a connector for the actual power wire to the motor brushes, sometimes it is soldered or crimped directly to that wire.docnjoj said:I have no idea about an epoxy connection but most brushed electric motors use a spring and a copper braid and motors carry a lot of current.
as i've said many times before, at the beach salt air corrodes everything, even remote controls in the house! So i can't use any contacts exposed to the air. By covering and sealing the contact area with JB WELD i hope to eliminate or delay for years corrosion. and as i said before, i've ordered a cell holder with spring to use as a jig to apply pressure TO A COPPER WIRE while the JB sets. once the joint is "shrink wrapped" in JB the spring is REMOVED and the cell is installed. i tested a spring because some people like flashlight springs, and didn't know how to test it. i rip them out because they are so bad.Hillhater said:Matt Gruber said:i tested a spring from a flashlight!
at 2.5A 208 mv drop! (remember my epoxy copper is 6 mv)
at 7 amps 608 mv drop and it burned my finger! (coppery/epoxy 12 mv)
i had this spring lying around because i soldered the wires last year direct to the cell, and put in a real switch and took out the spring. flashlight works perfect ever since. no flickers ever. next flashlight i'll use epoxy.
Matt, it has been said many times before,..you dont use the spring as the conductor, only to apply pressure to the contacts..like the way springs on a motor commutator work... or the way a rubber "spring" was used to apply pressure for the pack snath built here...
http://endless-sphere.com/forums/viewtopic.php?f=14&t=57810
If you are serious about cold contact systems, i suggest you redo your tests using a separate contact/conductor with the spring to just apply the pressure....then let us know what the volt drop is.
Doctorbass said:2009-2010-2011 ZERO MOTORCYCLES BATTERY ASSEMBLY METHOD:
One great and ingenious method that already was in use by zero motorcycle is to use copper braided strap with rubber ring to hold them on the top of neg and po of the cells! Then you can add a heatshrink to add pressure and avoid rubber to move.
Easy, cheap and easy to repair your pack.
for the rubber they used some bicycle tire rubber tube sliced to form some ring ! the advantage is that these rubber do not dry very fast and they are not too affected by moisture or temperature so they sustain pressure between the copper braided strap and cell tab very well!
Here is couples of pictures i took when i had to do some maintnance on a ZERO battery for a friend of mine. This battery was made to take 300A burst and i s a12P config meaning about 25A per cell tab and only holded by a rubber tensil pressure!
Please note that these are 26700 cells and each cylinder is in fact 2s1p ( 7.4V):
Doc
You can try a macro lens for a camera phone from eBay http://www.ebay.com.au/sch/i.html?_trksid=p2050601.m570.l1311.R1.TR11.TRC1.A0.H0.Xmacro%20&_nkw=macro%20lens&_sacat=0&_from=R40&_udlo&_udhi=16Matt Gruber said:i thinking of buying a CLOSE UP camera- any low price models u guys can recommend? I'd like you to see this JB up close.
liveforphysics said:No solder is the only way a pack can be manufactured and have acceptable cell failure rates for any lithium ion cell IMHO.
If you are getting the electrolyte above 120degC you are decomposing it as well as causing initiation points for other latent failure modes from solvent decomposition by-products that are now contaminating the cell.
I no longer consider it a pack construction topology I could recommend for any application.
Some guy on here has a brilliant easy DIY dimpled copper strip and the precisely critical low-compression-set foam that serves the function of the spring coil in your arrangement. A fat copper strip is multiple orders of magnitude less R than a coil of any of the springy metals.
cwah said:liveforphysics said:No solder is the only way a pack can be manufactured and have acceptable cell failure rates for any lithium ion cell IMHO.
If you are getting the electrolyte above 120degC you are decomposing it as well as causing initiation points for other latent failure modes from solvent decomposition by-products that are now contaminating the cell.
I no longer consider it a pack construction topology I could recommend for any application.
Some guy on here has a brilliant easy DIY dimpled copper strip and the precisely critical low-compression-set foam that serves the function of the spring coil in your arrangement. A fat copper strip is multiple orders of magnitude less R than a coil of any of the springy metals.
Even spot welding is non acceptable? but so many factories are doing that. Are they all wrong?
And It is the reason why JB weld desapears in the gap right away when you glue neodymium magnet to iron core.dnmun said:JB Weld does have metal in it. a fine powdered form of highly magnetic iron is incorporated into the resin. that is part of the reason it is used to repair metal fatigue cracks or cracked water jackets on engine block.