Author Topic: kWeld - "Next level" DIY battery spot welder  (Read 323546 times)

0 Members and 2 Guests are viewing this topic.

Offline carracing111

  • Contributor
  • Posts: 21
  • Country: ch
Re: kWeld - "Next level" DIY battery spot welder
« Reply #525 on: April 09, 2018, 09:43:33 pm »
Hi.

I charge the capacitors at 10V and 20A with a 60V, 20A power supply connected to another stepdown power supply (RD DPS5020)
At the moment it seems to work very well.

Regards
 

Offline carracing111

  • Contributor
  • Posts: 21
  • Country: ch
Re: kWeld - "Next level" DIY battery spot welder
« Reply #526 on: April 10, 2018, 11:15:18 pm »
I just tried Kweld with the supplied electrodes.
Everything seems to work fine, the calibration was successful although I believe that my capacitors are not able to supply the adequate power.

When I exceed 25J, after each welding Kweld restarts. It seems that the voltage falls below a minimum for a brief moment and this causes the restart.
With my old spot welder I do not have this problem since it uses an independent power supply. How can I solve this with Kweld? Is it possible to add an independent power supply?

I hope that with the supercapacitors works better.
I also need to set a power of 100J to get acceptable welds in pure nickel 0.15mm.

I have a feeling that Kweld needs a more powerful power supply.
Maybe the problem is in the added cable. My old welder connects directly to the capacitors and uses a much thicker electrode wire.

I have to continue testing but leaving aside the restart problem, the welds look great.

Regards
 

Offline tatus1969Topic starter

  • Super Contributor
  • ***
  • Posts: 1273
  • Country: de
  • Resistance is futile - We Are The Watt.
    • keenlab
Re: kWeld - "Next level" DIY battery spot welder
« Reply #527 on: April 11, 2018, 09:02:13 am »
I just tried Kweld with the supplied electrodes.
Everything seems to work fine, the calibration was successful although I believe that my capacitors are not able to supply the adequate power.
If you press and hold down the trigger switch when welding, then you should can read out the measured current. Use a low energy setting like 5J for that to obtain the current for fully charged capacitors.

The stock kWeld wires are optimized for the right current level with high current 3S Lipos. A significant part of the energy delivered by the power source is lost there. In your case, lower wire gauge will reduce that, allowing to use the stored energy more efficiently. How much Farad do the capacitors have?

The standard kWeld configuration with the Turnigy nanotech 3S has a system efficiency of approx 15%, which means that the power source needs to deliver 25J / 0.15 = 167J of energy per 25J pulse. It is important not to discharge the capacitors too deep, because weld power will drop with current raised to the power of 2. Your weld pulse should be as short as possible, in order not to allow heat spread away from the spot. You want the energy to stay concentrated in the small spot area. A good rule of thumb is to use 1/3 of the available capacitor voltage. When initially charged to 12V, you need at least a capacitance of C=2*167J / (12V^2 - (12V*2/3)^2) = 4.175F to achieve that.

When I exceed 25J, after each welding Kweld restarts. It seems that the voltage falls below a minimum for a brief moment and this causes the restart.
With my old spot welder I do not have this problem since it uses an independent power supply. How can I solve this with Kweld? Is it possible to add an independent power supply?
kWeld restarts when the input voltage drops below 3V approximately. But this also means, that the current flow has dropped down to a level that will probably not be enough to melt any more metal. This the reason why I think that it is does not make sense to add an auxiliary power input. It is possible though, you could directly attach a 12V supply to the electrolytic capacitor on the left, preferably with a series diode.


I hope that with the supercapacitors works better.
I also need to set a power of 100J to get acceptable welds in pure nickel 0.15mm.
The capacitor bank that I am developing has more than 200F, which means that there will be no significant voltage drop, even from big welds.

I have a feeling that Kweld needs a more powerful power supply.
Maybe the problem is in the added cable. My old welder connects directly to the capacitors and uses a much thicker electrode wire.
Yes, bigger wires help as explained above. The power switch has less resistance than any other similar device, but this advantage is being eaten up by the resistance of the 300A fuse. You could of course bridge that, but I wouldn't recommend it.
We Are The Watt - Resistance Is Futile!
 

Offline carracing111

  • Contributor
  • Posts: 21
  • Country: ch
Re: kWeld - "Next level" DIY battery spot welder
« Reply #528 on: April 11, 2018, 04:49:00 pm »
The values of the tests are the following:

CAL:
OFFS = 67, R = 2.84mR

Test 5J in nickel of different thicknesses

Test 1:
E = 5J, T = 2.19m, I = 1357A, R = 1.17mR

Test 2:
E = 5J, T = 2.34, I = 1370A, R = 1.07mR

The capacitors are 0.5F. They come from a very cheap car-audio brand, I buy them on offer at € 10 each pair. With luck there will be 3F among the 6 capacitors.

It is assumed that with 100J I could weld nickel of 0.3mm and this power is the one I need to weld nickel of 0.15. It seems that the capacitors deliver enough power (1370A), or not?

At the moment I do not intend to weld thicker nickel and the solderings to 100J in nickel of 0.15mm serve me.
The problem is that if I add Kweld in my welding head and restart it to each solder, then the power will be mismatched again, and I would have to reconfigure the soldering iron after each solder! That's why I've thought about adding a small independent source of energy.

Can you think of a better solution?

When will the supercapacitors be ready?

Thank you
« Last Edit: April 11, 2018, 04:52:54 pm by carracing111 »
 

Offline tatus1969Topic starter

  • Super Contributor
  • ***
  • Posts: 1273
  • Country: de
  • Resistance is futile - We Are The Watt.
    • keenlab
Re: kWeld - "Next level" DIY battery spot welder
« Reply #529 on: April 11, 2018, 07:02:28 pm »
The current level is very good, but as the capacitance is only 3F, this means that the voltage will drop very quickly, and the power that they can deliver into a weld is limited. You wrote that you are charging them to 10V. When they get discharged to 5V during a pulse (current will be only half at that moment), then the delivered energy is 0.5 * 3F * (10V^2 - 5V^2) = 112.5J. With an assumed system efficiency of 15%, this means that you should be able to reliably weld with up to 17J (kWeld setting). This is just enough for 0.1mm pure nickel, but thicker material needs bigger capacitors.


It is assumed that with 100J I could weld nickel of 0.3mm and this power is the one I need to weld nickel of 0.15. It seems that the capacitors deliver enough power (1370A), or not?
Your current capacitors have too little capacitance to hold up voltage during the pulse. They drain too quickly, and the current drops linearily with the voltage of course. Power into a resistive load (the weld spot) is proportional to current to the power of two, so that drops even quicker. So the answer is no, it is not enough for 0.15mm nickel.

At the moment I do not intend to weld thicker nickel and the solderings to 100J in nickel of 0.15mm serve me.
For 0.15mm nickel, the required energy should be 20-30J (estimated, I don't have that available), not 100J.

The problem is that if I add Kweld in my welding head and restart it to each solder, then the power will be mismatched again, and I would have to reconfigure the soldering iron after each solder! That's why I've thought about adding a small independent source of energy.
As I described, you can add an aux power supply if you like. But I would not recommend to discharge the caps to such a low voltage during a pulse, as described above and in my previous posts. Limit yourself to 17J and see what nickel thickness you can do with that. If you go higher, the results will not be as repeatable as you would expect, which is because the pulses get too long, current gets too low, and heat gets spreaded around the spot too much.

Can you think of a better solution?
Add more capacitance. I gave you a formula in my last post that allows you to calculate how much you need based on the pulse energy that you want.

When will the supercapacitors be ready?
I will receive the PCBs for the first prototype tomorrow, and the further timing depends on the results that I get.


I've made a quick simulation to visualize how quickly the output power from your capacitors drops. You can see that after just 4 Milliseconds, you are down from 13.6kW to 4.1kW:
« Last Edit: April 11, 2018, 07:10:13 pm by tatus1969 »
We Are The Watt - Resistance Is Futile!
 

Offline carracing111

  • Contributor
  • Posts: 21
  • Country: ch
Re: kWeld - "Next level" DIY battery spot welder
« Reply #530 on: April 11, 2018, 07:57:40 pm »
Thank you very much for all the explanations, I am learning a lot!

I will wait for the arrival of your capacitorsto continue the tests.

What I do not quite understand is because my Arduino Spot Welder works well with my capacitors. I can make good welds in 0.15mm nickel between 10-12ms. Maybe shorter pulses would be better but I think 10-12ms is within an acceptable range.

Regards
 

Offline tatus1969Topic starter

  • Super Contributor
  • ***
  • Posts: 1273
  • Country: de
  • Resistance is futile - We Are The Watt.
    • keenlab
Re: kWeld - "Next level" DIY battery spot welder
« Reply #531 on: April 11, 2018, 09:53:42 pm »
What I do not quite understand is because my Arduino Spot Welder works well with my capacitors. I can make good welds in 0.15mm nickel between 10-12ms. Maybe shorter pulses would be better but I think 10-12ms is within an acceptable range.
Have you wired up kWeld with the same beefy wires that you have been using with the Arduino welder? If not, then it would be like comparing apples and oranges. The losses in the stock kWeld cables are too high when you connect it to a limited power source like your capacitors. Both kWeld and the Arduino welder use a MOSFET switch, so you can expect the same welding result for the same pulse duration with both welders, and with the same wiring and power source.
We Are The Watt - Resistance Is Futile!
 

Offline tatus1969Topic starter

  • Super Contributor
  • ***
  • Posts: 1273
  • Country: de
  • Resistance is futile - We Are The Watt.
    • keenlab
Re: kWeld - "Next level" DIY battery spot welder
« Reply #532 on: April 12, 2018, 07:44:25 pm »
The supercapacitor PCBs arrived today, and I went to populate one. One remark if you are going to solder your own BCAP0310 parts: I used my 150W soldering iron for that task, the solder joints pull a lot of heat from the tip.

Getting the balancer to work properly took just a little longer than I anticipated, as it needed a few tiny (almost unnoticeable) tweaks:


Err, is it really already 10pm? What have I done during the last five hours? :o

Anyway... ready now for a full load test:

We Are The Watt - Resistance Is Futile!
 

Offline Kjelt

  • Super Contributor
  • ***
  • Posts: 6459
  • Country: nl
Re: kWeld - "Next level" DIY battery spot welder
« Reply #533 on: April 12, 2018, 09:35:45 pm »
Looks  8)
 

Offline tatus1969Topic starter

  • Super Contributor
  • ***
  • Posts: 1273
  • Country: de
  • Resistance is futile - We Are The Watt.
    • keenlab
Re: kWeld - "Next level" DIY battery spot welder
« Reply #534 on: April 13, 2018, 03:10:56 pm »
I am currently running an endurance test of the entire system, including the server PSU, the charger running at full power (average power delivery is around 500W), the new capacitor module with cooling fan (Scythe SY1225SL12SH), and the welder.

The system generates a 50J welding pulse into an artificial load once every two seconds. This is the maximum that the capacitor module can do continuously. It's steady state temperature is 58.5°C, which leaves enough headroom to their rated 70°C (room temperature is 25.0°C).

Without the fan, the capacitors are limited to a continuous repetiotion rate of once every 4 seconds. But as mentioned, this is the maximum average over several minutes of use, their thermal capacity is quite high and the welding electrodes heat up way quicker (I am currently working on improving this), so it is okay to make a series of welds as quickly as it can be handled.

Without a charger, the welding current measures 1050A. With the mentioned charger connected in parallel, the current is 1250A instead, as the charger helps to stabilise the capacitor voltage by delivering an additional 80A during the pulse. When using a different charger with less current, the results will be somewhere inbetween.

The 1050A is good enough for up to 100J welds or 0.3mm pure nickel strips. As the capacitors do not drop in voltage during the pulse (due to their high capacitance), the pulse duration is approximately linear: 5J = 3ms, 30J = 25ms, 100J = 94ms (each into a weld spot resistance of 1.2 mOhms).

Please let me know if you would like to get any other number that I haven't measured yet.

I plan to let the test make at least 10,000 pulses because I want to know if the capacitors experience any sort of damage or degradation from their use in this exotic application. Current pulse count is 2373, and there is no sign yet that the current would start dropping.

Here is a picture of the setup. This is actually a custom design that I am doing for a client project. The final setup will use two welders simultaneously (attached to the same one capacitor module) in an automated system.

We Are The Watt - Resistance Is Futile!
 

Offline tatus1969Topic starter

  • Super Contributor
  • ***
  • Posts: 1273
  • Country: de
  • Resistance is futile - We Are The Watt.
    • keenlab
Re: kWeld - "Next level" DIY battery spot welder
« Reply #535 on: April 16, 2018, 05:54:03 pm »
Endurance testing has finished after 10,000 pulses, and the capacitors held up very well! Here is how the weld current developed throughout the test. The starting current with fresh cells is 1250A. I have extrapolated the curve, and it would hit the 1000A mark after roughly 40,000 pulses. This is at full load and running the capacitors at a permanent temperature of approx 55°C (25°C ambient temp).

We Are The Watt - Resistance Is Futile!
 
The following users thanked this post: mzzj

Offline bicycleguy

  • Frequent Contributor
  • **
  • Posts: 265
  • Country: us
Re: low cost DIY battery spot welder [guesses on ... - solved]
« Reply #536 on: April 23, 2018, 12:47:27 am »
..
Thanks  :D It is performing extremely well. Even when doing a full pull (1kA for 200ms) the MOSFETs don't get even slightly warm. I am considering doing a test row by removing one after another to see how much I overdid it. ...

Hi, looks nice.  Did you ever try removing some MOSFETs
 

Offline SirJMD

  • Contributor
  • Posts: 26
  • Country: dk
Re: kWeld - "Next level" DIY battery spot welder
« Reply #537 on: April 26, 2018, 06:39:23 pm »
Perfect, thanks for the quick response.

I will order two boards without condensers plus a full board.
I could try 4S3P with my capacitors. I guess I can make some kind of adapter, so that the pins of my capacitors match.

I attach a couple of photos of my current capacitor configuration and with the welding head that will inherit my new Kweld!

If someone is interested in a head like mine, I can send detailed photos, explain how it works and offer a good price.

Regards

https://preview.ibb.co/hZaJ4x/20180330_122252.png

Where did you get the pneumatic head? And price?
 

Offline tatus1969Topic starter

  • Super Contributor
  • ***
  • Posts: 1273
  • Country: de
  • Resistance is futile - We Are The Watt.
    • keenlab
Re: kWeld - "Next level" DIY battery spot welder
« Reply #538 on: May 02, 2018, 08:04:24 am »
Just wanted to let you know that the capacitor module is now available for pre-orders at https://www.keenlab.de/index.php/product/kweld-ultracapacitor-module/! I expect to be able to deliver by beginning of June. The production batch size for this first round is not too big, and I expect not to be able to build up regular stock yet.
We Are The Watt - Resistance Is Futile!
 

Offline tatus1969Topic starter

  • Super Contributor
  • ***
  • Posts: 1273
  • Country: de
  • Resistance is futile - We Are The Watt.
    • keenlab
Re: low cost DIY battery spot welder [guesses on ... - solved]
« Reply #539 on: May 02, 2018, 08:11:05 am »
Hi, looks nice.  Did you ever try removing some MOSFETs
I did intensive robustness testing at current levels above its rating (which is 2000A), where I purposely destroyed a welder. kWeld failed after a few hundred pulses at 2800A. This is equivalent to an overload of a factor 2, because ohmic losses are proportional to the current squared. It was actually a MOSFET that failed, and this is the reason why I consider the number of paralleled transistors to be appropriate.
We Are The Watt - Resistance Is Futile!
 
The following users thanked this post: bicycleguy

Offline Kjelt

  • Super Contributor
  • ***
  • Posts: 6459
  • Country: nl
Re: kWeld - "Next level" DIY battery spot welder
« Reply #540 on: May 02, 2018, 05:49:28 pm »
Just wanted to let you know that the capacitor module is now available for pre-orders at https://www.keenlab.de/index.php/product/kweld-ultracapacitor-module/! I expect to be able to deliver by beginning of June. The production batch size for this first round is not too big, and I expect not to be able to build up regular stock yet.
Old news I ordered it already  :)  8)
 

Offline parasole

  • Contributor
  • Posts: 48
  • Country: md
Re: kWeld - "Next level" DIY battery spot welder
« Reply #541 on: May 04, 2018, 04:45:19 pm »
Here is my power bank setup, 100pcs of 10000uf cheap capacitors, provide perfect weld at 12.6V...
 

Offline tatus1969Topic starter

  • Super Contributor
  • ***
  • Posts: 1273
  • Country: de
  • Resistance is futile - We Are The Watt.
    • keenlab
Re: kWeld - "Next level" DIY battery spot welder
« Reply #542 on: May 04, 2018, 05:12:01 pm »
Here is my power bank setup, 100pcs of 10000uf cheap capacitors, provide perfect weld at 12.6V...
That is 1F in total, and when you charge them to 12.6V and allow them to discharge to 8V (I won't recommend to go lower, because current drops proportionally, hence output power drops quadratically), this corresponds to an energy delivery of 47 joules. I typically calculate a ballpark system efficiency number of 15% (the remaining 85% is lost in capacitor ESR, cabling, fuse, and welder switch), this allows you to weld with a pulse energy of up to 7.1 joules. This is just enough for 0.1mm nickel, but I doubt that you can do 0.2mm or 0.3mm with your setup.
We Are The Watt - Resistance Is Futile!
 

Offline parasole

  • Contributor
  • Posts: 48
  • Country: md
Re: kWeld - "Next level" DIY battery spot welder
« Reply #543 on: May 04, 2018, 08:29:54 pm »
That is 1F in total, and when you charge them to 12.6V and allow them to discharge to 8V (I won't recommend to go lower, because current drops proportionally, hence output power drops quadratically), this corresponds to an energy delivery of 47 joules. I typically calculate a ballpark system efficiency number of 15% (the remaining 85% is lost in capacitor ESR, cabling, fuse, and welder switch), this allows you to weld with a pulse energy of up to 7.1 joules. This is just enough for 0.1mm nickel, but I doubt that you can do 0.2mm or 0.3mm with your setup.

Sure you are right in your calculations, I just shared my experience and it serves me well. Having 100 caps helps greatly to reduce the ESR and operate with safe currents on individual capacitors. In the attempt to minimise the losses, I use quality awg6 welding cables and no fuse. Instead, I do charge the bank by using automotive bulb which provide quick recharge (about 5-7 sec, just enough time to prepare next welding position) and safety in case of any eventual FET failures and power sourse shorts.
The bank is dischaged to about 5V and provide robust and repeated result with 0.15mm I have used for my battery. I did not try thicker nickel since did not have it, however the way out is quite simple, or more capacitance or little bit more voltage, there is some room for it with 16V capacitors.
 

Offline tatus1969Topic starter

  • Super Contributor
  • ***
  • Posts: 1273
  • Country: de
  • Resistance is futile - We Are The Watt.
    • keenlab
Re: kWeld - "Next level" DIY battery spot welder
« Reply #544 on: May 05, 2018, 02:46:57 pm »
That is 1F in total, and when you charge them to 12.6V and allow them to discharge to 8V (I won't recommend to go lower, because current drops proportionally, hence output power drops quadratically), this corresponds to an energy delivery of 47 joules. I typically calculate a ballpark system efficiency number of 15% (the remaining 85% is lost in capacitor ESR, cabling, fuse, and welder switch), this allows you to weld with a pulse energy of up to 7.1 joules. This is just enough for 0.1mm nickel, but I doubt that you can do 0.2mm or 0.3mm with your setup.

Sure you are right in your calculations, I just shared my experience and it serves me well. Having 100 caps helps greatly to reduce the ESR and operate with safe currents on individual capacitors. In the attempt to minimise the losses, I use quality awg6 welding cables and no fuse. Instead, I do charge the bank by using automotive bulb which provide quick recharge (about 5-7 sec, just enough time to prepare next welding position) and safety in case of any eventual FET failures and power sourse shorts.
The bank is dischaged to about 5V and provide robust and repeated result with 0.15mm I have used for my battery. I did not try thicker nickel since did not have it, however the way out is quite simple, or more capacitance or little bit more voltage, there is some room for it with 16V capacitors.
The calculations result from my experiments, and findings that I came to with a customer here in Germany who was using 5 x 1F (huge) electrolytic audio capacitors. Even they don't provide enough energy for one 50 joulse pulse to weld 0.3mm nickel.

If you use 6AWG and no fuse, then this helps improving the efficiency and explains why you can do 0.15mm nickel.

Please don't get me wrong, I don't want to critizise your impressive design, just want to share my experience with smaller capacitors.
We Are The Watt - Resistance Is Futile!
 

Offline parasole

  • Contributor
  • Posts: 48
  • Country: md
Re: kWeld - "Next level" DIY battery spot welder
« Reply #545 on: May 06, 2018, 04:00:47 pm »
The calculations result from my experiments, and findings that I came to with a customer here in Germany who was using 5 x 1F (huge) electrolytic audio capacitors. Even they don't provide enough energy for one 50 joulse pulse to weld 0.3mm nickel.

If you use 6AWG and no fuse, then this helps improving the efficiency and explains why you can do 0.15mm nickel.

Please don't get me wrong, I don't want to critizise your impressive design, just want to share my experience with smaller capacitors.

Don't worry, I do not take it as critics, and sharing mutual experience I beleive is beneficial for the community... And your work and effort is no way to be underestimated.
Using audio caps may be the answer for poor performance, unfortunatelly almost all "modern" audio caps are just piece of junk and very few brands do provide the declared values. Before I built my caps bank I dig out as much as possible on this subject and got pretty good insight of audio caps quality from endless-sphere thread devoted to an SCR variant spot welder: https://endless-sphere.com/forums/viewtopic.php?f=2&t=2633. And on page 34 is an impressive report by Toorbough ULL-Zeveigh about their real quality: https://endless-sphere.com/forums/viewtopic.php?f=2&t=2633&start=825
Initially I bought 3pcs 0.49F caps, just to find out they are about 0.2F with quite high leakage, still not bad but quite not as declared for their cost :-) I even did try to open one, however found it to be fully embedded in paraffin without an aluminium can (and no brick inside ;), so decided better I will live it as is and use it considering measured capacity.
Any way, check out on page 40 green666 solution, his implementation nail down my decision to go by this route, real 1F (or more who wish for it) with very low ESR and leakage is proven to be an effective solution, altough it take more work to build it up.
« Last Edit: May 06, 2018, 04:09:25 pm by parasole »
 

Offline branadic

  • Super Contributor
  • ***
  • Posts: 2378
  • Country: de
  • Sounds like noise
Re: kWeld - "Next level" DIY battery spot welder
« Reply #546 on: May 06, 2018, 06:30:07 pm »
Just wanted to let you know that the capacitor module is now available for pre-orders at https://www.keenlab.de/index.php/product/kweld-ultracapacitor-module/! I expect to be able to deliver by beginning of June. The production batch size for this first round is not too big, and I expect not to be able to build up regular stock yet.

Question: The module available is a redesign of the pcb shown or the version with bodge wires? How do you charge the capacitor bank? Are there plans to offer a charger in near future as well as a complete welding system?

-branadic-
Computers exist to solve problems that we wouldn't have without them. AI exists to answer questions, we wouldn't ask without it.
 

Offline tatus1969Topic starter

  • Super Contributor
  • ***
  • Posts: 1273
  • Country: de
  • Resistance is futile - We Are The Watt.
    • keenlab
Re: kWeld - "Next level" DIY battery spot welder
« Reply #547 on: May 07, 2018, 08:15:32 am »
Using audio caps may be the answer for poor performance
My customer had been measuring them, and their ESR and capacitance was as expected. The initial current was >1000A. In his case, it is just the limited amount of capacitance that is keeping him from welding thicker material.

impressive report by Toorbough ULL-Zeveigh about their real quality: https://endless-sphere.com/forums/viewtopic.php?f=2&t=2633&start=825
Yes, they are very creative when it comes to alienate their customers: https://www.eevblog.com/forum/projects/kcube-led-cube-design-revisited/msg1482458/#msg1482458

Just imagine them putting that much effort and creativity into designing real products. That would be a real threat to the Western industry!

Question: The module available is a redesign of the pcb shown or the version with bodge wires? How do you charge the capacitor bank? Are there plans to offer a charger in near future as well as a complete welding system?
Yes of course :-) You'll only be able to buy professionally made and tested stuff from me (guaranteed without bricks or sand).

I am actually working on a charger (https://www.eevblog.com/forum/projects/guesses-on-what-i-am-attempting-here/msg1314337/#msg1314337) and have a prototype running under full load. But there is one problem with it. Its specifications are matched to allow full load operation of welder and capacitor module (one weld of 50J every second), and therefore it is capable of delivering 80A at 8.1V. This comes at a cost and I wouldn't be able to sell the charger module for less thanj 70€. But as many will be using the welder for casual operation and would rather spend some time waiting for recharge instead of spending that much extra money, this project is currently not at the top of my list.

My current low-cost proposal is to take an old AXT power supply, and feed the 12V into an adjustable buck converter. There are many of these like https://www.amazon.com/Aideepen-Constant-Current-Adjustable-Converter/dp/B0747QDRW9
« Last Edit: May 07, 2018, 08:17:37 am by tatus1969 »
We Are The Watt - Resistance Is Futile!
 

Offline HDRW

  • Newbie
  • Posts: 2
  • Country: gb
Re: kWeld - "Next level" DIY battery spot welder
« Reply #548 on: May 10, 2018, 01:37:51 pm »
Hi, newbie to this place (but not to electronics - learned which end of a soldering-iron gets hot at the age of 8!).

I want to "repair" cordless-drill battery packs, so Sub-C NiMH rather than the 18650s that a lot of people seem to be doing, and this project looks great for this.  I am very impressed with Frank's engineering and experimental approach.  I wish I was as conscientious!  :)

I see the kits are out of stock and I have signed up to be notified when the board-only kits are back in (I hope - haven't seen an acknowledgement).

Is there an ETA for the next batch of boards?

I'm on a tight budget (so the €100 capacitor kit is too much) and I'm not fond of mistreating Lithium batteries, but I have quite a selection of Sealed Lead Acid Batteries (SLAB) from my other hobby of Amateur Radio, but I haven't seen anyone mentioning this much, such as size of battery, using them in parallel, etc.

I have choices from about 7Ah to 80Ah (all 12V) but am mindful of how impressive shorting one of these can be!  Would it make more sense to mount the 300A fuse directly onto a battery terminal in this case, and connect the cable from it to the "far" side of where it would usually be?  That way a short anywhere, apart from directly across the battery terminals, would be protected.

Thoughts?

Cheers,
Howard
 

Offline carracing111

  • Contributor
  • Posts: 21
  • Country: ch
Re: kWeld - "Next level" DIY battery spot welder
« Reply #549 on: May 11, 2018, 10:16:39 am »
Perfect, thanks for the quick response.

I will order two boards without condensers plus a full board.
I could try 4S3P with my capacitors. I guess I can make some kind of adapter, so that the pins of my capacitors match.

I attach a couple of photos of my current capacitor configuration and with the welding head that will inherit my new Kweld!

If someone is interested in a head like mine, I can send detailed photos, explain how it works and offer a good price.

Regards

https://preview.ibb.co/hZaJ4x/20180330_122252.png

Where did you get the pneumatic head? And price?

Hi.

The machine, I get directly from the manufacturer Will Best. It is a brand that has been in the construction of welding machines for 19 years and it seems that the quality is quite good. I am very happy with my welding head.

They have offered me to distribute their machines in Europe, it's not something I'm going to take seriously...
The price that I offer is exactly the price they give me without earning anything. The idea is to get a discount on other machines that I plan to buy, such as a nickel cutter and ultrasonic welding machine.

The price of the welding head with double pneumatic system is of 880 dollars and the shipment by DHL (3 or 4 days) costs 121 dollars.
Maybe you can get a lower price with the system by springs. I think about 50-80 dollars less, like the one on the photos on my machine. I have both systems and soon I will install the double pneumatic system.

If you want detailed photos of any part or information do not hesitate to ask!

I add some pictures of the machine with the double pneumatic system

WBT_Q03_1_1" border="0

WBT_Q03_2_1" border="0

WBT_Q03_3" border="0
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf