Author Topic: kWeld - "Next level" DIY battery spot welder  (Read 323393 times)

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Offline Mikko Saarisalo

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #375 on: September 18, 2017, 06:45:10 pm »
+1 for the waiting list for next production run.  I would not mind making and paying a pre-order for one or two units.

(Just registered to this site for this very purpose... :) )

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Offline mcinque

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #376 on: September 24, 2017, 05:07:30 pm »
SirJMD, my compliments to you about how you're handling this little issue with your customers  :-+

Can I take advantage of this post to ask you the role of this three components (D16,D6 and D7-12, TVSs and zener) in your schematic? TVS are there to clamp voltage of course, maybe to manage the wiring inductance kickback? And why the zener on the mosfets? Of course to protect them from overvoltages, but are they needed because of the inductive kickbacks coming from the welding pulses?

Sorry for my ingorance  ;D
« Last Edit: September 24, 2017, 05:50:15 pm by mcinque »
 

Offline tatus1969Topic starter

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #377 on: September 25, 2017, 11:51:39 am »
SirJMD, my compliments to you about how you're handling this little issue with your customers  :-+
Thanks  ;)

Can I take advantage of this post to ask you the role of this three components (D16,D6 and D7-12, TVSs and zener) in your schematic? TVS are there to clamp voltage of course, maybe to manage the wiring inductance kickback? And why the zener on the mosfets? Of course to protect them from overvoltages, but are they needed because of the inductive kickbacks coming from the welding pulses?

Sorry for my ingorance  ;D
Yes, the TVS is there to reduce the stress that the transistors see during inductive kickback at turn-off. The zeners are there to protect the MOSFET gates from overvoltage. As I had to assume fast transients at their drains, and the gates are only loosely driven, I am afraid of gate overvoltage from charge build up through their Miller capacitances.
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Offline Fraser

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #378 on: September 25, 2017, 12:55:51 pm »
When dealing with high energies, the 'belt and braces' approach is more than justified  :-+

I would place TVS diodes all over the unit if I thought it were needed, but you have already come up with an excellent robust design.

Sadly my kit is still in its box awaiting its turn on my to-do list.

Off topic but maybe of interest ?

I was demonstrating my Chinese Transformer based battery tab welder to my neighbour at the weekend. My first weld resulted in a loud BANG, from inside the unit and its lights went out. I thought I had blown the fuse but no, it was fine. House power was still on as well. The give-away was the lack of the neon light on the power switch ..... no mains power was getting to it.

A quick look inside revealed no smell of burning or obvious failure. A continuity check proved that the mains power cable Neutral wire was open circuit. Further investigation revealed that the blue insulation on the wire after it entered the units case looked slightly discoloured white in a couple of places. I pulled on the cable and the insulation could be seen to stretch ! I cut open the wires insulation and found just white powder inside at two separate locations. The copper wire had turned to powder ! No signs of heat damage.... the copper was gone. I looked at the cable quality and found that the manufacturer had used really low current cable with very little copper cross sectional area and very fine strands in the insulated wires. I am not certain of the failure mode, be it corrosion or gradual erosion of the fine wires, but it gave up in the end. I am fitting decent quality 13A rated cable to it instead.

Fraser
« Last Edit: September 25, 2017, 01:08:50 pm by Fraser »
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Offline tatus1969Topic starter

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #379 on: September 26, 2017, 06:50:39 pm »
Sadly my kit is still in its box awaiting its turn on my to-do list.
Then it's time to let the Tiger out  ;)

a loud BANG, from inside the unit and its lights went out.
That reassures me to continue my work! I am busy sourcing components for a 100 unit production batch.
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Offline Southerner

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #380 on: September 26, 2017, 07:32:11 pm »

That reassures me to continue my work! I am busy sourcing components for a 100 unit production batch.
Do you have an estimated cost for the next batch?  I would be interested in one.
 

Offline tatus1969Topic starter

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #381 on: September 26, 2017, 07:33:43 pm »

That reassures me to continue my work! I am busy sourcing components for a 100 unit production batch.
Do you have an estimated cost for the next batch?  I would be interested in one.
I'll publish that once I have all prices from my suppliers. I expect that to be completed in 1-2 weeks from now.
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Offline tatus1969Topic starter

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #382 on: September 27, 2017, 08:32:59 am »
Guess what this will become  8)



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Offline Bratster

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #383 on: September 27, 2017, 08:40:57 am »
Capacitor charging interface for a server power supply?

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Offline Kjelt

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #384 on: September 27, 2017, 02:27:23 pm »
A raspberry pi / beaglebone  kWeld shield?  :popcorn:
 

Offline tatus1969Topic starter

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #385 on: September 28, 2017, 09:56:34 pm »
Capacitor charging interface for a server power supply?
Bang on!

A raspberry pi / beaglebone  kWeld shield?  :popcorn:
Would that be another product idea?  ;)
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Offline anishkgt

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kWeld - "Next level" DIY battery spot welder
« Reply #386 on: September 28, 2017, 09:58:56 pm »
Curious, which cad do you use to get those 3D images ?


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Offline tatus1969Topic starter

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #387 on: September 29, 2017, 10:53:25 am »
Curious, which cad do you use to get those 3D images ?
I'm using old-fashioned Eagle and export into Sketchup.
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Offline anishkgt

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #388 on: September 29, 2017, 11:00:50 am »
Oh ok well that is a lot of work to do. Eagle is fine but moving it to sketchup is some work. I guess kicad is better with 3D but have to manually link the symbol to the layout.


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Offline tatus1969Topic starter

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #389 on: September 29, 2017, 11:09:48 am »
Oh ok well that is a lot of work to do. Eagle is fine but moving it to sketchup is some work. I guess kicad is better with 3D but have to manually link the symbol to the layout.
the export/import is automatic, you just have to download or draw the objects. I get most of them through the warehouse, some of them are STEP files from the manufacturers. For this project, I didn't draw a single object from scratch. The biggest work was refining the heat sinks, as the manufacturer model only had a solid block instead of the fins.

I only wish that I had done that before ordering the PCBs. Look closer how the large connector's pins poke through the board :wtf:
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Offline anishkgt

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #390 on: September 29, 2017, 11:13:20 am »
Yea can be quite hard. I guess some day I'll have to start with kicad just because of the new licensing of eagle and the advantage of 3D rendering of kicad. If altium was cheaper would have taken that.


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Offline tatus1969Topic starter

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #391 on: October 01, 2017, 11:46:35 am »
Capacitor charging interface for a server power supply?
The boards from Elecrow have arrived much earlier than I expected. Ordered on 23rd, received on 27th. :-+

Although I have to work on sourcing components for kWeld, I couldn't resist to build and power up one. It instantly came up with all four phases, and voltage regulation also works already ;D

Target specs: output voltage 6-10V adjustable (the design can do 0-12), current 0-80A adjustable. The design can operate in CV and CC modes. It fits all HP DPB800GB DPS800GB server PSU models that I found so far on the internet.

Apart from being a high power super capacitor charger, it can also be used to build a 12V / 80A current limited PSU for less than 100€.

I'll have to see how much current the design can do continuously, but it has a temperature monitoring circuit that linearly reduces current and regulates a max temperature. This makes it suitable for permanent short circuit under all load conditions.


« Last Edit: October 01, 2017, 01:41:09 pm by tatus1969 »
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Offline Fraser

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #392 on: October 01, 2017, 11:55:15 am »
Nice work Frank  :-+

Very neat design.

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Offline anishkgt

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #393 on: October 01, 2017, 12:08:04 pm »
Good job frank. With a little mode I guess it should fit other psu as well. But don't you think the power supply for kweld is a bit oversized. Just my opinion.


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Offline tatus1969Topic starter

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #394 on: October 01, 2017, 01:37:48 pm »
Good job frank. With a little mode I guess it should fit other psu as well. But don't you think the power supply for kweld is a bit oversized. Just my opinion.
I want the system to allow welding at 50J with one second repetition rate. This means that the PSU needs to supply 50J / 0.1 * 1sec = 500W on average. (The 0.1 is the system efficiency)
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Offline anishkgt

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #395 on: October 01, 2017, 01:42:02 pm »
Cool sounds good enough.


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Offline joddi

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #396 on: October 04, 2017, 12:12:46 am »
I want the system to allow welding at 50J with one second repetition rate. This means that the PSU needs to supply 50J / 0.1 * 1sec = 500W on average. (The 0.1 is the system efficiency)

Nice target, but it also means your whole system has to be capable to disipate continuously 500W of heat somewhere...

I'm waiting for next batch of your electronics to order one. I need to weld copper braid to brass sheet with oposite electrodes, so probably more pulse energy will be necessary, but I don't care much about repetition rate (30s would be ok). I'm thinking of 500J pulses or maybe more and I'm prepared to double power MOSFET switch if necessary.
 

Offline tatus1969Topic starter

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #397 on: October 04, 2017, 08:42:02 am »
your whole system has to be capable to disipate continuously 500W of heat somewhere...
Most of the heat is dissipated in the super capacitors, which is why they will receive a decent fan. And this 50J/1sec target is not a continuous one, because the electrodes also receive substantial heat from the weld spot itself. A fixed electrode system could handle this, but the handheld system needs regular cooling breaks. I have set the 1sec goal because I do not want to limit the usability because one constantly had to wait for the capacitors to recharge.

I'm waiting for next batch of your electronics to order one. I need to weld copper braid to brass sheet with oposite electrodes, so probably more pulse energy will be necessary, but I don't care much about repetition rate (30s would be ok). I'm thinking of 500J pulses or maybe more and I'm prepared to double power MOSFET switch if necessary.
I don't think that kWeld is up to this task. I tried to weld two 0.1mm copper sheets together without success. Copper requires a significantly higher output power, and 1500A is not enough.
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Offline anishkgt

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #398 on: October 04, 2017, 09:19:39 am »
Kweld is intended for battery tab spot welding. Maybe you could do a diy spot welder with a MOT.


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Offline tatus1969Topic starter

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #399 on: October 06, 2017, 05:08:53 pm »
The capacitor charger test load has arrived, and I couldn't resist to make a first test with a higher load. Results: 35A at 8.5V -> 297W. Hottest spot of the charger are the large heat sink and the inductors: 50°C. It amazes me how small power circuits can be with modern components  8)

Sadly, I had to stop here because the server PSU seems to have problems, it reaches 105°C at one spot of its PCB. I'll have to solve that before continuing. I have another ten bulbs waiting (these are 50W).
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