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Re: 18650 spot welding -how to- ULTIMATE REPOSITORY

Posted: Jun 01 2015 2:18pm
by Electric Junk
Just a tip i was having problems stacking nickel strip for more amps so i sanded the top layer and it stuck better with less heat.

Re: 18650 spot welding -how to- ULTIMATE REPOSITORY

Posted: Jun 01 2015 8:50pm
by Nobuo
spinningmagnets wrote:I would like to add several things to take into consideration. The entire bottom and sides of an 18650 cell are the negative electrode. Only the "button" tip of the positive end is the positive elctrode. there is a small area of insulation between them on the positive end. The sides and even a small portion of the negative electrode that is at the edge of the positive end, is typically covered in a plastic sleeve, upon which the name and type is usually labeled.

Due to vibration over time, a short can develop across the positive central "button" electrode, and the circumferential negative "shell" that is very close to it. For this reason, many pack builders add some type of additional insulation. In the pic below, the 4-cell Paralleled string has a tan-colored paper insulator. Individual silicone "washers" are also available, at very affordable prices.

Image

In the pic below, the cell on the right has an additional "washer" style of insulator on the positive end.

Image

______________________________________________

The next item is adding a space between the places where the "two-probe" spot welder will create the welds. Due the variability of the thickness of the nickel strips, and also the resistance of one strip to the next, some of the spot-welding current will travel through the strip itself, rather than only through the places where the strip touches the exposed end of the cells. This is why production spot-welded packs have a short and thin "split" between one side and the other. This air-gap forces all of the spot-welding current to travel from one side, through the end of the cell, and then up through the other side. Doing it this way can create a more-consistent weld.

This slit can be added to plain nickel strip material with a dremel tool, using a thin abrasive disk.

Image
______________________________________________
Individual cell-fusing:

If one cell in the middle of a pack begins to short out and become very hot, very rapidly...having the connection between the cell and the rest of the pack formed as individual fuses can (in some cases) stop a runaway short from affecting the rest of the cells. The pack might still be ruined, but having only one cell overheat, rather than all of them....is a much more desirable situation.

The pic below is a design of a laser-cut nickel strip that connects one end of a collection of 12 cells, to form a 2S / 6P sub-group. The six tabs on the left side have the central split (described above), and those would be spot-welded onto the negative ends. The six tabs on the right side not only have a central split, they also have the connection from the center out to the rest of the cells formed with four thin "S" shaped strands. These are the fuses. All four strands would get very hot during a shorted cell, and...as soon as one of them melted completely through, the current flowing through fewer fuses would cause an immediate cascading failure of the remaining three strands. The fuse "strands" are to be located on the postive "button"

Image
Thank you very much with this extended considerations. I really appreciate how well explained it is. :o I actually had an idea of all you mentioned except about the small gap some nickel tabs have in the middle of the welding spots. That's really interesting.

About the insulation "washers" I would add, that some cells like Panasonic or LG ones had a double layer of insulation around the anode (it is really like a plastic spacer inside the insulation wrap) so if the pack is clever spot welded and then is consciously covered with anti-vibration pad, I think it would be made enough secured for years without the need to add spacers, although it is always a good improve.

The nickel gap I'm sure it make a difference on >=0.15mm thick strips, where sometimes nickel disintegrate making a hole, or stick harder on the pole than on the cell. For thinner strips as 0.1mm I have a stone-strong clean weldings with 20A - 25A welding current and standard pure nickel strips.

I really like the individual cell-fusing method for a very appreciable increase on security for a hard fail/short cell. The well-known discussed thing is that it makes resistance points, and it only would work for a specific max continuous amps cell range. (I don't know if that tabs are made in different thickness/fuse points sizes). Also are not a very reliable tab depending on your configuration / shape cells method, like offset "pyramidal" hot glued cells. I think that a pack with factory new, high quality, same batch, spot welded cells and a conservative max discharging rates with a good BMS, had a very low fatal fail rate.

Despite my small thoughts, this info is gold and essential for what a Ultimate repository must be! :D

I will add the information in the head post if you are agree.

I am, and sure the whole ES battery scene, truly grateful for your contribution spinningmagnets

Re: 18650 spot welding -how to- ULTIMATE REPOSITORY

Posted: Jun 01 2015 9:13pm
by Nobuo
mlt34 wrote:I'd like to submit a how-to I wrote up on building 18650 ebike packs - I took a lot of pictures along the way of one of my builds to try and make a very clear walk through: http://www.ebikeschool.com/how-to-build ... 650-cells/
I read the whole thing! you are an awesome communicator, as I wish I would ever be.. :evil:

I really liked where you solder the BMS monitoring wires :o I will take that into account for my next packs. Also the safety tips are consistent, I think the article itself has everything it really need to be a reference, I'm sure that will be a must for the future newcomers :wink:

I just have a small two appreciations. The one other just mentioned about cutting the strips a little more when are welded on the anodes, just for minimize the chance for a short there and also saving material!

Also what I think we talked before in our flash conversations :mrgreen: that I prefer to shrink wrap the pack directly over the spot welded cells. Because that really acts like another layer of glue, molding in the shape all is connected / soldered pushing everything to stay in its place and insulated. So I would add the anti-vibration pad after the shrink wrap.

I will link your article on the head post if I have your permission.

Thank you very much for sharing, it is a really honour!

Re: 18650 spot welding -how to- ULTIMATE REPOSITORY

Posted: Jun 02 2015 5:13am
by mlt34
Nobuo wrote:Also what I think we talked before in our flash conversations that I prefer to shrink wrap the pack directly over the spot welded cells. Because that really acts like another layer of glue, molding in the shape all is connected / soldered pushing everything to stay in its place and insulated. So I would add the anti-vibration pad after the shrink wrap.
That's true, I had forgotten about that but now I remember us talking about that. I will have to give that a try.
Nobuo wrote:I will link your article on the head post if I have your permission.
Absolutely, I'd appreciate it! I'm amazed by how much people have shared that article already. In less than a day it has as many hits as other articles I wrote over a year ago!

Re: 18650 spot welding -how to- ULTIMATE REPOSITORY

Posted: Jun 08 2015 3:06am
by usertogo
While not directly related to 'spot welding' but tangentially, as way to prevent shorts between cells, and possibly as good pack building measure in order to provide air circulation in between cells, I would like comments on the spacer brackets as they appear in a picture about 5 posts up, or can be seen here: http://www.aliexpress.com/item/18650-ba ... 48430.html
I have been thinking about the alternative to 3d print my own brackets, but since my printer is still 'work in progress' and my pack is materializing faster, I wonder if there are better alternatives, and what they are? The pack I am building is a 24S15P LiFePO 18650 based on 1500mAh Heter Goldencell (China)
Thanks! :P

Re: 18650 spot welding -how to- ULTIMATE REPOSITORY

Posted: Jun 08 2015 4:57am
by Nobuo
I would like to clarify something: :roll:

Enclosed and static air remaining between cells does not help them cooling better than if they are in contact. Since air does not flow (because the batteries commonly are finished with insulating wrapping/packaging), the heat transmission is actually reduced with air gaps.

When cells generate heat, the exterior is always cooler, so the heat is cooled down always from the exterior surface of the battery pack. So you need to transmit the heat to the exterior the faster the better. Air is indeed in essence a heat *insulator* if you compare with solids. Only flowing air can dissipate heat. So unless that air gaps between the cells are actively flowed, they are just heat containers.

So the brackets/holders help with the squaring, symmetric and organized shape of the pack, exchanging a cell slightly easily, and for welding the premade squared tabs, but not with the heat dissipation. I'm agree it would help a bit to avoid a short because the nickel tabs are not in contact with the surface, so they are not pressed.

So do you want alternatives to the brackets/holders? or another different ones?

Nowadays are cheaper and easy to use if you buy manufactured than making it with PLA/ABS on your 3D printer

Re: 18650 spot welding -how to- ULTIMATE REPOSITORY

Posted: Jun 08 2015 7:03am
by usertogo
Is just physics. When cells generate heat, the exterior is always cooler, so the heat is cooled down always from the exterior surface of the battery pack. So you need to transmit the heat to the exterior the faster the better. Air is indeed in essence a heat insulator if you compare with solids. Only flowing air can dissipate heat. So unless that air gaps between the cells are actively flowed, are just heat containers.
Not to worry, physics comes very natural to me, and I am thinking thermodynamics even when I cook or bake! So that's why I don't like tight packs either, because the cells on the perimeter are nice and cool while in the middle they are sweating blood! Of course I would have an escape for heat at the top possibly active cooling with sensors, Arduino controlled fan adding cool air, or maybe for the winter recirculation of heat from the top to the bottom!
Anyhow the cells are ordered, so is the BMS, Nickel and charger, I just hate that Aliexpress sellers don't seem to ship immediately like ebay sellers, and the brackets can never match my specs quite as well as my own design and neither be as cheap as if I could print them myself! So alternatives are sought while I wait that the bracket seller even responds to a question!

Re: 18650 spot welding -how to- ULTIMATE REPOSITORY

Posted: Jun 08 2015 9:33pm
by John in CR
I haven't worried about a physical separation between the two plastic "wrappers" unless the voltage difference is more than one cell in which case I simply add a layer of duct tape. I do glue the cells together with a couple of thin strips of polyurethane glue, and I typically opt for a staggered alignment instead of square for the minimum height as well as a stronger glued structure (each cell touches more cells).

I've received a lot of pre-made blocks of cells that are hot glued together, and hot glue doesn't work worth a damn on those plastic sleeves. It may seem like it holds at first, but it's not a good bond. I've pulled off hundreds of hot glue strips without damaging a single fragile plastic wrapper. I don't want my battery structure supported just by the tab welds, because then vibrations can cause movement between cells opening the door for different types of failures.

If you ever plan to solder something to the tabs near the button end, then yes add paper O-rings before tab welding. The plastic ones don't seem to have a very high melting point.

For great flexibility in pack shape, using building blocks of 5p or 7p in a trapezoid shape works great...like this
7p 18650 blocks.JPG
7p 18650 blocks.JPG (12.75 KiB) Viewed 6080 times
The red X's were to show my agent in China to make sure the tab doesn't extend into those spaces, which could cause issues later when stacking. The button end gets and extra few cm of tab consistently off to the same side, so you're soldering or welding that extra tab to the flat cell end of the next block.

Trapezoid blocks work great for making a cylindrical pack by making your series connections end-to-end forming one half, and then back, so the pos and neg terminals are at the same end of the cylinder. Plan your series connections very well ahead of time. With today's high capacity 18650's 5p trapezoids end-to-end wrapped in glass cloth, and then 2 strings of those wrapped in carbon to form the main tubes of an ebike sure is interesting to me. 8)

Re: 18650 spot welding -how to- ULTIMATE REPOSITORY

Posted: Jun 09 2015 2:16pm
by mlt34
John in CR wrote:For great flexibility in pack shape building blocks of 5p or 7p in a trapezoid shape works great...like this


...I seem to be missing any picture or diagram. Which is a shame, because this sounds very interesting!

Re: 18650 spot welding -how to- ULTIMATE REPOSITORY

Posted: Jun 09 2015 2:50pm
by John in CR
mlt34 wrote:
John in CR wrote:For great flexibility in pack shape building blocks of 5p or 7p in a trapezoid shape works great...like this
...I seem to be missing any picture or diagram. Which is a shame, because this sounds very interesting!
Sorry about that. I was running out as I submitted and forgot to upload the image. Now it's fixed.

Re: 18650 spot welding -how to- ULTIMATE REPOSITORY

Posted: Jun 09 2015 3:02pm
by spinningmagnets
I will add the information in the head post if you are agree
I only collected this information from the posts of others who are much more experienced than me. Feel free to use this info in any way that is helpful, and thank you for starting this helpful thread.

edit: here are some cell configurations for a 12S / 5P pack in a triangle shape (using just two sub-pack shapes). I was wondering about this when supower111 was spot-welding the 5P packs, and all the builder had to do is solder the sub-packs together.

OOOOO OOOOO OOO
OOOOO OOOOO OO
OOOOO OOOOO
OOOOO OOO
OOOOO OO
OOOOO
OOO
OO

OOOOO OOOOO OOOOO OOO
OOOOO OOOOO OOOOO OO
OOOOO OOOOO OOOOO
OOOOO OOOOO

Re: 18650 spot welding -how to- ULTIMATE REPOSITORY

Posted: Jun 10 2015 12:58pm
by StinkyGoalieGuy
Any idea if this crazy plan would work:
1) Buy a Harbor Freight Spot welder:

120 Volt version: http://www.harborfreight.com/120-volt-s ... 61205.html
or
240 Volt version: http://www.harborfreight.com/240-volt-s ... 61206.html

The 240 seems to have better reviews, but not everybody may have access to a 240 outlet. You also have to put your own plug on that one.

2) Attach a set of probes at then end of flexible wire to the existing probes so you can you weld with both probes in parallel as would be needed when welding batteries. I'm thinking maybe some copper needles at the end of some welder cable?

What I like about this is that Harbor Freight is near me and I can buy and warranty/return this if necessary, instead of dealing with shady Chinese companies. It's also cheap, especially when you add in the 20% coupons that are always floating around. I can also use it to spot weld sheet metal as well if I go back to the original probes.

Comments and critique please!

Re: 18650 spot welding -how to- ULTIMATE REPOSITORY

Posted: Jun 10 2015 3:33pm
by StinkyGoalieGuy
StinkyGoalieGuy wrote:Any idea if this crazy plan would work:
1) Buy a Harbor Freight Spot welder:

120 Volt version: http://www.harborfreight.com/120-volt-s ... 61205.html
or
240 Volt version: http://www.harborfreight.com/240-volt-s ... 61206.html

The 240 seems to have better reviews, but not everybody may have access to a 240 outlet. You also have to put your own plug on that one.

2) Attach a set of probes at then end of flexible wire to the existing probes so you can you weld with both probes in parallel as would be needed when welding batteries. I'm thinking maybe some copper needles at the end of some welder cable?

What I like about this is that Harbor Freight is near me and I can buy and warranty/return this if necessary, instead of dealing with shady Chinese companies. It's also cheap, especially when you add in the 20% coupons that are always floating around. I can also use it to spot weld sheet metal as well if I go back to the original probes.

Comments and critique please!
Looks like my idea would not work very well. Those Harbor Freight welders don't appear to have any pulse adjustment. It's a simple turn it on for however long you want, then turn it off.

Re: 18650 spot welding -how to- ULTIMATE REPOSITORY

Posted: Jun 14 2015 6:38am
by prensel
I'm creating an 36S30P pack of Samsung INR18650-29E for my Vectrix VX1 motorscooter.

For extra protection a drew up this in Illustrator and cut some black sticker material in the sign cutter.
foto-4.JPG
18650 cell stickers

Re: 18650 spot welding -how to- ULTIMATE REPOSITORY

Posted: Jun 14 2015 9:48am
by litespeed
Great idea.

Tom

Re: 18650 spot welding -how to- ULTIMATE REPOSITORY

Posted: Jul 20 2015 2:28pm
by rojitor
This is a kickass guide nobuo. Thanks a lot for posting it. I have no place at home right now for Spot welder and stuff but eventually I'd try to do my pack and I will count on this.
Tu molas tío.

Re: 18650 spot welding -how to- ULTIMATE REPOSITORY

Posted: Jul 20 2015 2:58pm
by okashira
prensel wrote:I'm creating an 36S30P pack of Samsung INR18650-29E for my Vectrix VX1 motorscooter.

For extra protection a drew up this in Illustrator and cut some black sticker material in the sign cutter.
foto-4.JPG
Wow... a scooter with the battery energy of a Volt.
What kind of controller/motor?

Re: 18650 spot welding -how to- ULTIMATE REPOSITORY

Posted: Jul 20 2015 3:33pm
by 999zip999
150 volts 87ah wow.

Re: 18650 spot welding -how to- ULTIMATE REPOSITORY

Posted: Aug 23 2015 4:16pm
by tomjasz
Nickel on sale today! Verified source. Order using app for even more savings 10meters for $15 shipped!

http://aliexpress.com/item/Free-shippin ... dVersion=1

Re: 18650 spot welding -how to- ULTIMATE REPOSITORY

Posted: Aug 24 2015 10:20am
by Nobuo
Really good deal for start welding, I bought them once, verified quality.

Thanks for sharing!

Re: 18650 spot welding -how to- ULTIMATE REPOSITORY

Posted: Aug 25 2015 2:15pm
by Synon
Nice! Thanks for sharing the nickle strip deal, just bought some.

Anyone know how to add a timer to a welder?
I recently made my own spot welder with a microwave transformer. I used one of the door switches to make a foot switch to turn on the welder, however my results are very inconsistent. If I could have the welder turn on for a specific amount of time I'm sure that would drastically help me get more consistent welds, I'm sure there is just a cheap ebay part I need to order to make this happen, anyone know what piece I need or where to find it?

Re: 18650 spot welding -how to- ULTIMATE REPOSITORY

Posted: Aug 26 2015 9:00am
by ridethelightning
can anyone recomend a source of 0.15-0.2mm Ni coated copper strip?

Re: 18650 spot welding -how to- ULTIMATE REPOSITORY

Posted: Aug 26 2015 2:59pm
by tomjasz
Best way to buy nickel and best price. Buy a kg! Micah calls this a great source. I couldn't invest that much right now but will soon. After I have more batts. I have to say the JP Welder is fantastic. Now that I have a deign for a 10s3p mini batt I'll weld it up as soon as the new material arrives.

I have 1kg of nickel plated but will likely just sell that off cheap.

http://www.aliexpress.com/item/FREE-SHI ... 48107.html

Re: 18650 spot welding -how to- ULTIMATE REPOSITORY

Posted: Aug 27 2015 8:13am
by Monstarr
I bought the $80 spotwelder for a 26650 LiFePO4 pack rebuild.
But I encounter a problem, hope someone here can help out.

I am using nickelstrip 0,15x10mm and current setting 25 A. As you may know in The Netherlands we have 230 VAC single phase with 16 A circuitbreakers at least.
But whenever I try to make a weld between batterycell and nickelstrip the circuit breaker trips.
The threshold seem to be at 23 A but this and lower setting don't give a good enough weld.
I see everybody here using and promoting 0,15mm nickelstrip.

What is causing this problem? Device is rated @ 1 KVA.

Re: 18650 spot welding -how to- ULTIMATE REPOSITORY

Posted: Aug 27 2015 9:54am
by Punx0r
Try a Type B circuit breaker - these are used for devices with large inrush currents (motors, transformers) to prevent nuisance tripping.