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Author Topic: kWeld - "Next level" DIY battery spot welder  (Read 26151 times)

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Offline ovnr

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #350 on: September 12, 2017, 08:52:37 AM »
Tatus: I haven't kept up with the thread as much as I probably should have, but any plans for another batch of kWelds?
I wanted one, but had already spent a bit too much money on other frivolous things that month.
 

Offline ozwolf

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #351 on: September 12, 2017, 08:58:42 AM »
Tatus: I haven't kept up with the thread as much as I probably should have, but any plans for another batch of kWelds?
I wanted one, but had already spent a bit too much money on other frivolous things that month.

Same here...
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Offline HackedFridgeMagnet

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #352 on: September 12, 2017, 09:07:16 AM »
+1 for me
 

Offline tatus1969

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #353 on: September 12, 2017, 08:29:13 PM »
+1 for me
Tatus: I haven't kept up with the thread as much as I probably should have, but any plans for another batch of kWelds?
I wanted one, but had already spent a bit too much money on other frivolous things that month.

Same here...
Tatus: I haven't kept up with the thread as much as I probably should have, but any plans for another batch of kWelds?
I wanted one, but had already spent a bit too much money on other frivolous things that month.
I'm already busy sourcing components : :)
Your living is determined not so much by what life brings to you as by the attitude you bring to life; not so much by what happens to you as by the way your mind looks at what happens.

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Offline tatus1969

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #354 on: September 13, 2017, 02:06:16 AM »
A customer had reported a kWeld that had its main voltage regulator broken (see picture). He is using a 6S Lipo instead of the recommended 3S. After some research, I realized that I paid much attention to the robustness of the power switch while overlooking what is happening at the battery terminals. Of course that also sees high voltage spikes from inductive kickback, which is exceeding the main regulator's input voltage ratings.

Although it never happened to me during all my experiments that the regulator broke down, I highly recommend applying the modification that I summarized in the attached document. If you do not have the resources to do this by yourself, then of course I offer to have the unit sent back to me, modified, and delivered back to you, all free of charge.

Your living is determined not so much by what life brings to you as by the attitude you bring to life; not so much by what happens to you as by the way your mind looks at what happens.

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Online Fraser

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #355 on: September 13, 2017, 02:20:15 AM »
Frank,

You are a true Gentleman. It is obvious from your posts.

Your design is, by its very nature, a kind of ongoing development project. It is not unreasonable to expect the odd issue or two, in spite of your careful and thorough testing before production.

If I were wishing to return a board to you for rework, I would want to pay all postage costs. It just seems unfair to expect you to pay such on this project. It is not like you are making some huge profit on the kit is it ! That is just my old fashioned way I suppose. I can implement any changes needed myself anyway so you will not be receiving a board from me :)

Keep up the great work and thank you again for sharing this excellent project with us. Doing so risks experiencing undiscovered issues that can be a hassle to sort out for 'customers'. I hope you do not suffer any hassle due to sharing your unit with us. You do not deserve such.

Fraser
 
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Offline SirJMD

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #356 on: September 13, 2017, 04:24:34 AM »
A customer had reported a kWeld that had its main voltage regulator broken (see picture). He is using a 6S Lipo instead of the recommended 3S. After some research, I realized that I paid much attention to the robustness of the power switch while overlooking what is happening at the battery terminals. Of course that also sees high voltage spikes from inductive kickback, which is exceeding the main regulator's input voltage ratings.

Although it never happened to me during all my experiments that the regulator broke down, I highly recommend applying the modification that I summarized in the attached document. If you do not have the resources to do this by yourself, then of course I offer to have the unit sent back to me, modified, and delivered back to you, all free of charge.



Very nice of you to support your "customers" the way you offer to. Highly appreciated.

Great work!
 
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Offline tatus1969

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #357 on: September 13, 2017, 06:57:09 AM »
Your design is, by its very nature, a kind of ongoing development project. It is not unreasonable to expect the odd issue or two, in spite of your careful and thorough testing before production.
Yes, which is why I wanted to wait for your all feedback and also you all (ab)using it, before ordering a next, larger batch. Although I should do this timely, there are so many people knocking on my door now  :)
Your living is determined not so much by what life brings to you as by the attitude you bring to life; not so much by what happens to you as by the way your mind looks at what happens.

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Online Fraser

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #358 on: September 13, 2017, 07:07:34 AM »
Frank,

I will always be using my kWeld on 14V or less so is there any reason why I should not fit a lower voltage TVS better matched to my maximum intended supply ? I was thinking of one that engaged at say 20V and fully clamped at say around 22V. It's working voltage of 18V would prevent any unwelcome issues with a fully charged car battery p.d.

Best Wishes

Fraser
« Last Edit: September 13, 2017, 07:13:04 AM by Fraser »
 

Offline tatus1969

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #359 on: September 13, 2017, 07:16:23 AM »
Frank,

I will always be using my kWeld on 14V or less so is there any reason why I should not fit a lower voltage TVS better matched to my maximum intended supply ? I was thinking of one that engaged at say 16V and fully clamped at say around 20V.

Best Wishes

Fraser
Yes, that would leave much more safety margin. And it would also allow you using a PTC / resettable fuse of lets say 0.5~2 ohm instead of a resistor. The 10 ohm resistor adds ~0.5V of voltage drop from the battery (operating current is 40-50mA, with pulses of ~300mA during holdup capacitor recharge). I'll revise the entire supply circuit in the next revision, and tend to use a linear regulator with enough input voltage rating instead. Power dissipation will be 1W at 30V, but who cares at welding power in the kW range...
Your living is determined not so much by what life brings to you as by the attitude you bring to life; not so much by what happens to you as by the way your mind looks at what happens.

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Online Fraser

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #360 on: September 13, 2017, 07:48:02 AM »
Many thanks Frank. That is what I will do on my kWeld them.

Fraser
 

Offline anishkgt

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #361 on: September 13, 2017, 11:19:15 AM »
silly question here. Forgive me for that.

what does the ohm mean here ? resistance of the nickel between the two points at which the elctrodes touch ? or the wire during weld ?
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Offline tatus1969

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #362 on: September 13, 2017, 05:21:46 PM »
silly question here. Forgive me for that.

what does the ohm mean here ? resistance of the nickel between the two points at which the elctrodes touch ? or the wire during weld ?
It displays the measured resistance between the electrode tips. EDIT: this is true when welding. During calibration, it displays the combined wiring/electrode holder resistance at the output. So somehow both of your answers are correct. And it shows that your question was not silly  :)
« Last Edit: September 13, 2017, 07:02:36 PM by tatus1969 »
Your living is determined not so much by what life brings to you as by the attitude you bring to life; not so much by what happens to you as by the way your mind looks at what happens.

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Offline tatus1969

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #363 on: September 13, 2017, 07:10:23 PM »
Many thanks Frank. That is what I will do on my kWeld them.
One more thought: a 0.5R polyfuse is maybe too little resistance. You have to assume that the inductively driven voltage at the input is ~50V. When your TVS clamps at 20V, then the current would be (50-20)/0.5=60A. If the TVS can sufficiently clamp this current, then you're fine. Otherwise it may be wise to increase the resistance. At 2 Ohms, the current is reduced to 15A which I like much more. Power dissipation is not an issue, because the voltage spikes last less than 20 microseconds.
Your living is determined not so much by what life brings to you as by the attitude you bring to life; not so much by what happens to you as by the way your mind looks at what happens.

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Online Fraser

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #364 on: September 13, 2017, 08:49:23 PM »
Hi Frank,

Thanks for the advice. I will add a little resistance as you suggest.

I have elected to use a P6KE18A TVS rated at 100A so it is quite robust. I already have them in my component stock so may as well use them 🙂

Best Wishes

Fraser
« Last Edit: September 14, 2017, 05:35:46 AM by Fraser »
 

Offline anishkgt

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #365 on: September 14, 2017, 01:23:13 AM »
Maybe a bit off topic.

Just need to clear my doubts on getting amps and resistance put into the nickel strips by this formula
I = U * diameter [mm2] / (0.0175 * length [m])

with that i get this result
I = 0.29 * 25 / (0.0175 * 0.13)
  = 3,186A for 20ms


How true is this ? i did start a thread on this but am just curious and lost at the same time as to how to calculate it without any additional components or costly gadgets.
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Offline tatus1969

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #366 on: September 14, 2017, 03:02:35 AM »
I = 0.29 * 25 / (0.0175 * 0.13)
Please elaborate more on the numbers, except for the specific resistance of copper (not nickel) I cannot see how you came to them.
Your living is determined not so much by what life brings to you as by the attitude you bring to life; not so much by what happens to you as by the way your mind looks at what happens.

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Offline anishkgt

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #367 on: September 14, 2017, 03:16:50 AM »
Oh i am sorry that i missed that out

I = 0.29 * 25 / (0.0175 * 0.13)
V = 0.29 (on a cable with two tapping 13cm apart)
size of cable in mm2 = 25
0.0175 is a constant (not sure what it is but i got the formula from here http://avdweb.nl/contact/12-contacts/1-avandalen.html)
distance between two taps on the cable = 13cm (here 0.13m)
« Last Edit: September 14, 2017, 03:21:00 AM by anishkgt »
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Offline SirJMD

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #368 on: September 14, 2017, 06:33:46 AM »
Just finished testing copper strips and copper wire. No success at all. I think the copper conducts way too good.
 

Offline tatus1969

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #369 on: September 14, 2017, 07:26:23 PM »
Just finished testing copper strips and copper wire. No success at all. I think the copper conducts way too good.
I did some quick research on this. To weld copper strips, one supposedly needs 2500A+, tungsten electrodes, an inert gas. There is also an interesting thread here: https://endless-sphere.com/forums/viewtopic.php?t=84680
Your living is determined not so much by what life brings to you as by the attitude you bring to life; not so much by what happens to you as by the way your mind looks at what happens.

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Offline tatus1969

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #370 on: September 14, 2017, 07:29:07 PM »
Oh i am sorry that i missed that out

I = 0.29 * 25 / (0.0175 * 0.13)
V = 0.29 (on a cable with two tapping 13cm apart)
size of cable in mm2 = 25
0.0175 is a constant (not sure what it is but i got the formula from here http://avdweb.nl/contact/12-contacts/1-avandalen.html)
distance between two taps on the cable = 13cm (here 0.13m)
That is Ohm's law combined with https://en.wikipedia.org/wiki/Electrical_resistivity_and_conductivity
Your living is determined not so much by what life brings to you as by the attitude you bring to life; not so much by what happens to you as by the way your mind looks at what happens.

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Offline anishkgt

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #371 on: September 14, 2017, 07:30:42 PM »
Yes but how reliable would it be ?
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Offline tatus1969

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #372 on: September 14, 2017, 07:33:15 PM »
Yes but how reliable would it be ?
What do you mean by that?
Your living is determined not so much by what life brings to you as by the attitude you bring to life; not so much by what happens to you as by the way your mind looks at what happens.

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Offline anishkgt

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #373 on: September 14, 2017, 07:34:50 PM »
I mean can we determine the amp draw using this method, that is with that formula ?
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Offline tatus1969

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Re: kWeld - "Next level" DIY battery spot welder
« Reply #374 on: September 14, 2017, 07:36:28 PM »
I mean can we determine the amp draw using this method, that is with that formula ?
Did you take the time to understand the wiki article and relate it to the formula? That should answer your question.
Your living is determined not so much by what life brings to you as by the attitude you bring to life; not so much by what happens to you as by the way your mind looks at what happens.

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