kWeld - "Next level" DIY battery spot welder

[cs.dk]

Just courious about your product, but can you reliably weld 2 thicker plates together, lets say 0,8 mm sheet metal? If so, i could in deed be interested in one.

[Fraser]

Interesting to read about the 8mm2 size. That explains why that size is not present in the 8T version of my crimper I wanted the smaller sizes for when I do projects that require a metal tube to be crimped down onto a cable or rod. The tubes can be non standard diameters so having the 8mm2 die just looked to be useful

For smaller automotive type terminals I use the insulated ones and have the correct good quality crimping tool to compress them. The crimper even indents the plastic sleeve with the die details ! That crimping too was quite expensive but when dealing with automotive electrical connections, I take no chances.

I managed to get nice quality bootlace ferrule crimping tool a few years ago. Using bootlace ferrule crimps certainly tidies up my terminal block connections. Love that tool

Fraser

[tatus1969]

Just courious about your product, but can you reliably weld 2 thicker plates together, lets say 0,8 mm sheet metal? If so, i could in deed be interested in one.

I'm afraid but I have no experience with that. Do you know what current levels and pulse times are required for that? The power switch of my welder electronics can reliably withstand 2kA for 200ms.

I found this interesting site: http://www.portablewelders.com/spot-welding-technical

It suggests at least 6kA for 200ms. The switch resistance of my welder is 120 microOhms. A current of 6kA would result in a power dissipation of 4.3kW, or 720W per transistor (assuming equal distribution, which is not the case). According to the datasheet of the used transistors, they allow a maximum pulse duration of 10ms at this power level. Which means: no, the kWeld circuit cannot do that for the required 200ms.

I managed to get nice quality bootlace ferrule crimping tool a few years ago. Using bootlace ferrule crimps certainly tidies up my terminal block connections. Love that tool

I'm still searching for the one that crimps well and is affordable. I have very good professional work experience with the Knipex 5512, that is in my opinion the one and only. Because that one is very expensive, I bought a "clone" for personal use - and I am quite disappointed. It is not machined precisely enough to do >=22AWG crimps.

[Kjelt]

The even more expensive knipex with six crimpsides was half price on amazon a half year back perhaps still. The reason was they made a new one that went two steps in awg further but who needs that. So scored one for 105 euros instead of al ost 200 and every crimp is a pure delight.

[cs.dk]

I'm afraid but I have no experience with that. Do you know what current levels and pulse times are required for that?

I have no idea - But you have a working device next to you

[tatus1969]

I'm afraid but I have no experience with that. Do you know what current levels and pulse times are required for that?

I have no idea - But you have a working device next to you

That, yes. But no .8mm sheet metal

[Fraser]

My 10T hydraulic lug crimping tool arrived today.

I must say I am very impressed with it. How do they manage to make such a relatively complex tool and sell it for so little ? The tool is well designed and made from what I can see. The pump action Is quick as apparently the design provides fast initial movement until resistance is felt, then the action slows down. Turning the pressure release knob results in very quick retraction of the lower die and piston. On the10T version, the die locating pins appear to be a better design than those seen on the 8T version. They snap into the die holders and the dies remain well retained and aligned.

For occasional use, I can certainly recommend this tool.

Fraser

[tatus1969]

My 10T hydraulic lug crimping tool arrived today.

I must say I am very impressed with it. How do they manage to make such a relatively complex tool and sell it for so little ? The tool is well designed and made from what I can see. The pump actio. Is quick as apparently the desig. Provides fast initial movement until resistance is felt, then the action slows down. Turning the pressure release knob results in very quick retraction of the lower die and piston. On the10T version, the die locating pins appear to be a better design than those seen on the 8T version. They snap in to the die holders and the dies remain well retained and aligned.

For occasional use, I can certainly recommend this tool.

Fraser

I already regret it that I went for the cheaper option...

[tatus1969]

A quick progress update on this project:
- production of 25 copies electronic module is progressing well. I had a delay of one week here waiting for the microprocessors from Arrow, but the parcel is now at customs clearance here in Germany (there was some annoyance regarding export control restrictions, I had to calm Mr Trump that I will not be building any rockets from them). The PCBs have been manufactured in the mean time.
- I have completed the firmware update functionality. All that is needed for that is a terminal program that can talk YMODEM (extraPutty and TeraTerm do this job well), an adapter cable (will be added to the shop for a few €), and an Arduino style FT232 USB->UART adapter configured for 3.3V operation (I will also sell them via the shop for convenience).
- I have designed a housing for the welder, see these pictures and please tell me how you like it. I'll upload it so that anyone can print it. I'll not be selling them in my shop, as I don't have a 3D printer.

I still wait for the new battery and some parts to make a video showing the new stuff, hopefully by this weekend 

[Fraser]

I like the case. Very nice design.

Thank you for the update on the first 25 modules . I am in no great rush as I have other projects in flow along with selling off my excess test gear on eBay I will be happy to receive my module whenever it is convenient for you to ship it. I am just pleased that I have pre-ordered one to ensure I get it.

Fraser

[tatus1969]

I think that it will still be possible to keep delivery by mid August, I will keep you updated. Had to call DHL customs yesterday to hear that they have high workload and would have eventually contacted me the next days because they need an EORI number from me. 

[tatus1969]

I've been working on the assembly manual, and have just uploaded a first (incomplete) version to the kicksurfer website. I have made this a downloadable product in my store that is free of charge for all registered users: https://www.kicksurfer.de/index.php/product/assembly-manual/  That'll not help much against far east copiers, but maybe a bit...

And I have tested a different approach to manufacture the bus bars, the brass bars are just too expensive to finish. I have attached first pictures. These are laser-cut from 4mm x 12mm x 75mm aluminum bars. The first tests are very promising, the switch resistance goes up from 0.12 to 0.145 micro-ohms. That is just 25 micro-ohms more. They don't heat up noticeably during heavy firing.

Their price is quite good, so that for all people who have already purchased the brass bars, I can offer the following:
- if you have ordered them "raw" you can choose to receive the finished aluminum bars at no extra cost
- if you have ordered them "finished", I'll additionally refund the labor cost

Of course it'll also be okay to leave an order untouched.

I'll create a separate mail to all customers to ask for their wishes.

[Fraser]

My only concern regarding using Aluminium for the buss bars is the high reactivity of aluminium with the atmosphere. Aluminium oxide is a very poor conductor. Brass will also oxidise. Copper buss bars may be the best option, but also the most expensive.

I was considering what protection the bars may need to prevent such oxidisation becoming an issue over time. The old trick was to cover the area around the contact surface with an air excluder such as vaseline petrolium jelly. This may need to be considered but I do not think it is good to use it on the actual contact surface itself.

Fraser

[Kjelt]

I've been working on the assembly manual, and have just uploaded a first (incomplete) version to the kicksurfer website. I have made this a downloadable product in my store that is free of charge for all registered users: https://www.kicksurfer.de/index.php/product/assembly-manual/  That'll not help much against far east copiers, but maybe a bit...

Great  , I just can't find the download button but ordered it so I expect you will mail it ? 

And I have tested a different approach to manufacture the bus bars, the brass bars are just too expensive to finish.

What was the problem, the milling is it to tough or does the bit bite into the metal? It might be good as Fraser indicates to switch to Copper, but I will look into this myself.
Can you provide me (us) with the exact mechanical layout (thickness, length, wideness, and position of the holes and diameter) of the bars, than I can look at my local metaldump if I can find a suitable copper donorpiece and already start cutting it up and working on that   
Do you think it would matter if the barr is made out of two or three parallel parts or perhaps made thicker, since it is the overall resistance that counts right?

[Fraser]

Kjelt,

You need to 'order' the manual and go through checkout as if you were buying it. You then see a link to click for the download in your checkout receipt. No charge is made to you and no card/PayPal is needed. It just requires you to log in.

Fraser

[Kjelt]

Yes thanks, the email had some delay but it is all clear now 

[tatus1969]

Kjelt,

You need to 'order' the manual and go through checkout as if you were buying it. You then see a link to click for the download in your checkout receipt. No charge is made to you and no card/PayPal is needed. It just requires you to log in.

Fraser

thanks for helping me out 

[tatus1969]

My only concern regarding using Aluminium for the buss bars is the high reactivity of aluminium with the atmosphere. Aluminium oxide is a very poor conductor. Brass will also oxidise. Copper buss bars may be the best option, but also the most expensive.

I was considering what protection the bars may need to prevent such oxidisation becoming an issue over time. The old trick was to cover the area around the contact surface with an air excluder such as vaseline petrolium jelly. This may need to be considered but I do not think it is good to use it on the actual contact surface itself.

I've got the same feedback on other places, and I have started investigating it. I found a shop that sells galvanic articles, and it would be possible to add chemical zinc, and then galvanize with gold. That would be a good match for the gold PCB traces.

On the other hand, I have built an audio amplifier decades ago, and I still have the bulk capacitors with screw terminals that are connected with aluminum bars. The capacitor's screw terminals were made from tinned brass.

That makes me think: would it prevent contact corrosion if I would order tinned PCB's instead of gold plated next time?

What was the problem, the milling is it to tough or does the bit bite into the metal? It might be good as Fraser indicates to switch to Copper, but I will look into this myself.
Can you provide me (us) with the exact mechanical layout (thickness, length, wideness, and position of the holes and diameter) of the bars, than I can look at my local metaldump if I can find a suitable copper donorpiece and already start cutting it up and working on that   
Do you think it would matter if the barr is made out of two or three parallel parts or perhaps made thicker, since it is the overall resistance that counts right?

I indeed had problems with drills biting into the metal, but meanwhile I have specialized soft metal drills that perform much better. The work steps on the brass bars are the following:
- cut to length
- measure and centerpunch all drill positions (I will use a template instead for "mass" production)
- drill 4.5mm holes
- drill 6.5mm holes
- deburr with countersink drill
- sand all faces

That sums up, wich was why I decided to set the price for that work relatively high. Also to prevent myself from drowning in machining work.

Here are the dimensions of the original brass bars. The new aluminm bar is identical but is only 4mm thick (the maximum that my provider can laser with this contour).

[Kjelt]

Thanks for the info Frank  Itsure takes time if you do all those steps,almost time for a CNC 

[tatus1969]

almost time for a CNC 

definitely!!

[Fraser]

I have been looking at the cost and availability of 12.7mm x 12.7mm copper bar. In the UK it will cost me around £10 inc postage. As I am doing the machining myself I am tempted to go with copper bars. I may find some thinner copper bar cheaper as 12.7 x 12.7 is overkill. One nice property of copper is that its ovidation does not interfere with conduction. Hence its use in building utility mains bus bars

Fraser

[kony]

Get the aluminium busbars nickel plated. Cheap & effective corrosion protection.

[tatus1969]

I just ordered some bottles of chemical nickel plating solvent, it is not very expensive and I will treat all sold aluminum bus bars with that. For aluminium, they sell an "activator" fluid.

[tatus1969]

I have been looking at the cost and availability of 12.7mm x 12.7mm copper bar. In the UK it will cost me around £10 inc postage. As I am doing the machining myself I am tempted to go with copper bars. I may find some thinner copper bar cheaper as 12.7 x 12.7 is overkill.

The  wisdom A Lot Helps A Lot is in fact true here  Anyhow, I have calculated the ohmic resistance of the new 4x12x75mm alu bus bars with 48 micro ohms...

One nice property of copper is that its ovidation does not interfere with conduction. Hence its use in building utility mains bus bars

The problem was that I have a cheap laser cutting service at hand, and they don't offer copper. They're already ordered as aluminum.

[tatus1969]

Just wanted to share this with you before going to sleep. Today the XT90 plugs arrived that I was waiting for. As the battery came with them, I wanted to test the suitability of these before cutting the wires and soldering XT150. First conclusion: they do not support insertion of AWG8.

What is more interesting is the first data that I captured from the new Turnigy nano-tech 3S / 5Ah / 130C (=650A) battery. The welder has measured an impressive current of 1230A. The oscilloscope diagram taken from (almost) the battery terminals shows a voltage drop of 6.56V at this current. This results in an internal resistance of these beasts of only 5.3mOhm. That is comparable to what is achievable with supercapacitors. Now the battery has to show how well it likes currents at this level (as specified, this is only 1.9 times of rated current). I will do a stress test in a new video this weekend.