Low-power no-solder idea...

[cal3thousand]

So what we need is a low temp solder to be made. Maybe graphene paste in the future?

[Punx0r]

At least it has been established just how bad a spring connection can be

There are some very low melting-point metal alloys, but I don't know if they will stick to other metals.

[Hillhater]

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/viewto ... 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.

[TheBeastie]

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?
Thanks.

[amberwolf]

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.

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.


Even so, because of the arcing across commutator/brushes, the springs often see a lot of heat--but that heat isn't because of anyting the spring does, electrically (as the spring isn't part of the circuit, as it would be in hte proposed battery pack).

[Matt Gruber]

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/viewto ... 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.

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.
.
i get JB WELD at wal-mart. the slow cure type, about $5.
on ebay it costs more, so maybe the price went up?

[dogman dan]

I get it. That could work. Especially for 1c type loads or less. Or you could use a furniture clamp, or other method of applying the pressure. JB weld can be amazingly strong in some applications. Still just a pressure connection, but with lower resistance copper hopefully doing a decent contact.

Interesting idea. Of course if you had a spot welder, like the factories in china, you'd just use that. I'll be very interested to see how this experiment turns out.

Just had a thought. Doesn't JB weld have metal in it? Maybe not. If it conducts, can't cover the can much on the + side. It won't stick so great to the plastic shrink cover. You might look at marine grade PC7. Very slow cure, and high temp.

[Matt Gruber]

my meter says jb has infinite ohms.
as for 1c, what fun is that? sony VTC4 or sony VTC5 30amp, 60 amp peak 2-2.5ah. i would test at 15amp as my scooter peaks at 15. if it works i can run 10s1p since last time at the car show it only used 0.9ah.
todays test 2 ring connectors, 1 is tinned copper, the other cheap thin aluminum. just experimenting on old dead cells. i was fixing my scooter and had a little JB left over. the hole in the center isn't ideal, but they were available in quantity
Looks like i'd do this in 2 stages.
1st epoxy connector with little JB.
test it. if it passes the v drop, slather on plenty of JB to insulate, and make a STRONG joint that won't come apart. If the connection gets worse over the long term, it will probably heat up and melt the JB just enough to kill power, alerting me that a repair is needed. that's just a guess as JB doesn't melt easily, they say 400F+ i think. it works on car radiators so it can take some heat.

[Matt Gruber]

so yesterday i charged one of these dead, 0v cells, before , it would go dead in 1 day. today it held the 4.06!
so why not do a discharge test thru the epoxy connection? BUT i was careless when i set it down, and the wires shorted
before i knew it there was a puff of smoke and one JB wire fell off! WOW this is FANTASTIC since it fell off before the built in thermal fuse could react! it got very warm, i'd guess 110-115F, there was a lot of amps flowing for about 3 seconds.
so the cell can be used for more LIVE experiments. it still has 4.02v. i used a razor blade to scrape off the JB.
SO THE JB WELD ACTS AS A FUSE! THIS IS GREAT! Like a dream come true!
for those that don't know, i'm using sony US18650V from makita packs. Once the thermal fuse blows, it can't be changed and the cell is trash.

[cal3thousand]

Pictures?

[marty]

http://endless-sphere.com/forums/viewto ... ry#p758973

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

[cal3thousand]

^ Some one is selling those very modules in the Market section right now

[dogman dan]

Interesting idea. Cut up road bike tube for 18650's?

[Matt Gruber]

JB changes the game for me. Now i can run any high power cell(not just Konions) and have a cheap effective external fuse, that happens to hold the wire firmly against the cell. And insulate the pack to prevent shorts. Those bare packs you guys are so proud of look scary to me.
My packs are small, so i dont mind the overnight set time. JB does sell a quick set epoxy for those in a hurry.
I tested some 15a fuses and the v drop was 70 mv on the best ones. others, the rejects were 90-110 mv.(at 15 amps)
I'm going to predict that it will be a long time until this catches on, like on that video where a guy could not make jb conduct to save his life. too dim witted to apply pressure to make a good connection
For now, i have an EXCLUSIVE method.

[Matt Gruber]

So i made up a wood holder and used a block of wood against the cell, and a spring to maintain pressure as it cured, 3 cells on this test, all working, 2 from the dead pile but now holding a charge.
good thing i used a red wire on the + because both ends looked the same, solid JB. very hard to find any bare area to measure the v drop...
so i cut a tiny spot, and they were all 4 -5 mv!
JB gives short protection as the JB wants to cover and insulate anything not pressed tight.
this is about 3C discharge, so no mercy. they got warm in 2 minutes, but the connections stayed either the same or maybe not as warm.
Will test again before i buy any cells without tabs. No bare copper on these, only factory tinned wire, so they should conduct excellent for years, I hope.
For now i'm testing in my -9 scooter. Gave it 5 seconds WOT for 5c and none of the fuses blew. Will not be doing this again, 3-4c is normal pulling away from a stop. That is plenty for 2011 sony konions. They are past their prime years. Due for old age home soon

[TheBeastie]

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.

You can try a macro lens for a camera phone from eBay http://www.ebay.com.au/sch/i.html?_trks ... o&_udhi=16
Or what about a USB microscope are pretty cheap, most don't have stands that don't get in the way.

http://www.ebay.com/sch/i.html?_trksid= ... &_from=R40

[kiwipete]

Or this: turn your smart phone into a microscope: http://www.instructables.com/id/10-Smar ... onversion/

[liveforphysics]

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]

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?

[cal3thousand]

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?

He is mentioning SOLDER. Much different process than spot welding. Spot welding uses a high current impulse to create a small weld. It's so fast that the heat build-up is minimal. Compare that to solder, which requires a certain melting temperature for solder to flow, and holds the heat on the joint for much longer.

[dnmun]

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.

[parabellum]

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.

And It is the reason why JB weld desapears in the gap right away when you glue neodymium magnet to iron core.

[Matt Gruber]

so i got my $1 18650 single cell holder. not worth $1 imo, but i see where a guy got 50 for $20.
easy to upgrade. there is a rivet on each end with a hole in it, that a 14awg fits. (comes with 24awg)
so i passed the bare 14 wire thru the rivet, and folded it over and soldered it to firm it up and reduce corrosion. On the neg it passes thru the spring, then folds over to contact the cell. the spring presses the copper wire against the cell. So if the OP wants to do this instead of spot weld or solder, i don't see a low-med power problem. would be easy to pop the cells out now and then, to clean contacts and test. I could see easy service as the pack weakens with age. Say the range is down 20%, after the ride, pop out the cells and do a 5 second high amp bench test. those that sag the most, get replaced. Or if they are pretty much even, you know it is time to replace, or add a 2nd pack in parallel.