18650 spot welding -how to- ULTIMATE REPOSITORY

[Nobuo]

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-a-diy-electric-bicycle-lithium-battery-from-18650-cells/

I read the whole thing! you are an awesome communicator, as I wish I would ever be..

I really liked where you solder the BMS monitoring wires 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 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!

 

[mlt34]

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.

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!

 

[Nobuo]

I would like to clarify something:

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

 

[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


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)

 

[mlt34]

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!

 

[John in CR]

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.

 

[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

 

[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-spot-welder-61205.html
or
240 Volt version: http://www.harborfreight.com/240-volt-spot-welder-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!

 

[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-spot-welder-61205.html
or
240 Volt version: http://www.harborfreight.com/240-volt-spot-welder-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.

 

[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.

 

[litespeed]

Great idea.

Tom

 

[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.

 

[okashira]

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.

Wow... a scooter with the battery energy of a Volt.
What kind of controller/motor?

 

[999zip999]

150 volts 87ah wow.

 

[tomjasz]

Nickel on sale today! Verified source. Order using app for even more savings 10meters for $15 shipped!

http://aliexpress.com/item/Free-shipping-18650-battery-nickel-strip-0-15mm-nickel-plate-li-ion-cell-nickel-belt-Cylindrical/2050759694.html?recommendVersion=1

 

[Nobuo]

Really good deal for start welding, I bought them once, verified quality.

Thanks for sharing!

 

[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?

 

[ridethelightning]

can anyone recomend a source of 0.15-0.2mm Ni coated copper strip?

 

[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-SHIPPING-High-Quality-Pure-Nickel-Plate-Strap-Strip-Sheets-99-96-for-battery-spot/2054948107.html

 

[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.

 

[Punx0r]

Try a Type B circuit breaker - these are used for devices with large inrush currents (motors, transformers) to prevent nuisance tripping.

 

[meelis11]

Try a Type B circuit breaker - these are used for devices with large inrush currents (motors, transformers) to prevent nuisance tripping.

I had also similar problem - when turned welder on then breaker tripped. Connected welder to kitchen socket where normally electric oven is connected and no problem anymore, even when using 5m extension cord.

 

[Punx0r]

The oven is usually on a dedicated 30A circuit so will supply a welder with more current without tripping the breaker

 

[meelis11]

The oven is usually on a dedicated 30A circuit so will supply a welder with more current without tripping the breaker

I know - just use whatever you have to solve problem - it is easier to use already available socket with more powerful breaker than replace existing one with type B or more powerful one.

 

[Arlo1]

Thanks for all the info.