LASER WELDING aluminum to copper battery tab

[Doctorbass]

Some guys from the electric motorcycle project called EMUS projet are using this technique to weld their battery connections.

It look pretty well!

 

[will_newton]

I just happen to own a laser welder and was wondering this very thing. Lasers have a lot of advantages, one of the main advantages for ebikes is that you can make a solderless connection. The laser is intense enough to make a fusion weld of the material, so there is a continuous connection with no voltage drop. I would say that in some cases you get a better connection than the original material because the laser burns out impurities as it welds.

It's very cool, you can fuse dissimilar metals such as steel to gold and as DocBass has shown above, copper to aluminum. The light beam actually creates a new alloy of the joined metals. The most similar process to lasering, as far as technique is TIG welding. You use a filler rod, but the rod is made from the same material as what you're welding and is very tiny, 28 gauge (.3 mm).

Another advantage is the VERY localized heat applied. I can weld with a .5 to 2 mm beam and hold the object in my bare hand while welding. This is useful for jewelry, since it allows you to work on items that would be impossible to repair using a traditional torch.

Only problem is that they are a bit cost prohibitive for the Average Joe. A small benchtop model from a reputable dealer can start as low as $16,000 and run on up into the stratosphere. Expect to spend $20-$25000 USD for your average lipo joining needs.

Here's mine: http://www.laserstar.net/welding-products/990-iweld.cfm I have the 80 joule model.

 

[Hillhater]

couldnt you do this tab connection (copper to Alu) with a spot Welder ??

 

[bigmoose]

Doc, I have been thinking about ultrasonic welding of the tabs. I have seen one used at work to ultrasonically weld a 6mm copper tube closed, but not to weld aluminum to copper. We need to come up with a good tab connection method that is better than what we have now.

I Googled it again, and hit the mother load. Manufacturer even shows the battery tab application!
http://www.techsonicultrasonic.com/index.php?option=com_content&task=view&id=12&Itemid=9&lang=en

Inside the machine http://www.powerultrasonics.com/content/ultrasonic-metal-welding

We can buy the raw ultrasonic rings here for 4 euro's each
http://www.ultrasonicsworld.com/index.php?main_page=index&cPath=3_5

I think this is a weld head generator for a little under 400 euros
http://www.ultrasonicsworld.com/index.php?main_page=index&cPath=1

Now we need Texas Pyro to build us a prototype ultrasonic tab welder for under $1,000 bucks in parts and were done!

 

[Doctorbass]

Doc, I have been thinking about ultrasonic welding of the tabs. I have seen one used at work to ultrasonically weld a 6mm copper tube closed, but not to weld aluminum to copper. We need to come up with a good tab connection method that is better than what we have now.

I Googled it again, and hit the mother load. Manufacturer even shows the battery tab application!
http://www.techsonicultrasonic.com/index.php?option=com_content&task=view&id=12&Itemid=9&lang=en

Inside the machine http://www.powerultrasonics.com/content/ultrasonic-metal-welding

We can buy the raw ultrasonic rings here for 4 euro's each
http://www.ultrasonicsworld.com/index.php?main_page=index&cPath=3_5

I think this is a weld head generator for a little under 400 euros
http://www.ultrasonicsworld.com/index.php?main_page=index&cPath=1

Now we need Texas Pyro to build us a prototype ultrasonic tab welder for under $1,000 bucks in parts and were done!

Hmmm that's interesting!

I found this one that is really interesting.. ! it is for coppe rto copper cable terminaisons:

( note the low harmonics sound that the camera audio recording system is making dur to the saturation!

Doc

[youtube]Fvw_ZadxFrQ[/youtube]

 

[texaspyro]

Now we need Texas Pyro to build us a prototype ultrasonic tab welder for under $1,000 bucks in parts and were done!

I once looked into what it would take to do an ultrasonic welder... definitely a lot of obstacles for a home builder. 1000W ultrasonic transducers don't seem to grown on trees. Maybe a surplus sonar transducer might be a start, but their operating freq is probably way too low. Instead of a piezo type transducer, you might be able to use some kind of voice coil arrangement... anybody got any kilowatt tweeters?

The driver electronics are doable. Not much different from what a BLDC controller does (10-40 KHz pwm signal) You do need some feedback circuitry to tune the freq to the resonant freq of the transducer.

Things start to slip into the Black Magic Ju-Ju Realm with things like the ultrasonic "booster" system and coupling the ultrasonics into the tooling. That gets back into resonant cavity designs, etc.

Another nasty show stopper is the tooling and clamping system. The fixed anvil and ultrasonic "hammer" are rather complex hardened tool steel with a magic textured surfaces. Also the clamping pressure tends to be rather high (like 1000+ pounds).

A related welding technique is friction stir welding. It uses a spinning hardened probe to heat the metal via friction. Used to weld aircraft panels, rocket boosters, etc. It can weld 2+ inch thick plate.

 

[bigmoose]

I am glad you joined in! I take your advice to heart. So to the scrap pile the thought of fabricating our own ultrasonic welder.

That brings us perhaps back to your magical spot welder? ... Now how do we get it to make a series of spots the width of the tab? With the "right" pressure, can we spot weld aluminum tabs to copper tabs? Can we fab conductive rollers and suitable loading pressures? Is your current capability too low? Do the spots have to be spaced apart to get enough current to fuse our tab materials?

Pyro, your good at this! It is just begging for a solution. These tabbed cells should start to hit the secondary market in a year or so in quantity... we sure could use a good tab connection solution!

 

[texaspyro]

I have not had a whole lot of success welding copper to aluminum. Most of my tests were .005-.010 copper to .032 Al... I would get good very bonding at the weld, but tug on the copper and it pulls off the Al. Firmly bonded to the copper is a pimple of Al and there is a corresponding divot in the Al. It looks like the Al melts at the weld, bonds to the copper, but at the point where the Al no longer melted it becomes brittle or separates from the welded material.

I don't know how the battery tab material would behave... nothing to try it on.

I'm not sure of the best mechanics for doing pouch cell tabs. Probably just do a series of spots on the tabs with opposed weld electrodes (or a tweezer) would be good.

You might be able to fab some linear electrodes that would weld a line of material. The tabs are fairly light weight material so you can get a lot of heat into them over an area bigger than a spot. One problem might be that would make a nice linear weld, but cut the tab at the weld line. Another issue would be making sure that the electrodes were nice and square to the material. I didn't have much success with flat ended hand-held electrodes...