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kWeld - "Next level" DIY battery spot welder

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    The JP Welder is also a nice unit.


      I'm Todd and I have a kWeld,

      I've never spot welded before but I thought I could do it. After assembling the welder, getting a battery to run it and a charger for the battery, I was ready to learn. I had purchased some .15 nickel strip and also have some cut 8mm pieces from Sunstone welding to weld with.

      Setting the welder at 20J then 30J then 10J and doing some test welds on strips I got it dialed in enough to try on cells.

      I have a Shark battery with PF cells that I looked inside and noticed it could benefit from some added nickel strips, this would be the first project. This is a 14s 4p battery that sagged from day one and some doubled up strip wouldn't hurt and I could practice.

      The cut strips work really well as it is the serial connections I'd be doing and 1 1/4, (30mm) fits well. I managed to add lots of strips, even desoldered and resoldered the bms wires with added strips, really nice welder with easy one knob control and the lipo battery lasts a while, I only charged when I was finished back to storage Lipo charge.

      Really happy with it but it is a DYI thing, you assemble it and take all responsibility for it's use. I have started adding strips to a second battery that needed it, until I blew a diode, whoops, I'm not sure how it happened but I've been emailing Frank the maker and there are a few new diodes in the mail that I will solder in place. I sent some testing videos for Frank to check and we found it was a blown diode, I have the diode desoldered from the board and waiting for the mail to finish the second battery.

      Then I have 2 custom shapes to make.

      This welder makes the welding of strips to cells easy but you still need to be very careful in every aspect of battery building, lots of care and clean habits, shorts can be prevented.


        Todd - Many thanks for your little review. That is very helpful!

        Had you ever used any other spot welders before? Any comments on how they compare? Ease of use? Quality of the connections?


          Originally posted by thebootfitter View Post
          Todd - Many thanks for your little review. That is very helpful!

          Had you ever used any other spot welders before? Any comments on how they compare? Ease of use? Quality of the connections?
          Here is a calculator for battery layout with different shapes.


          • Scoonie
            Scoonie commented
            Editing a comment
            It is shape layout only. Not for configuring battery connections. Just clarifying.

          Welder is up and running again after receiving parts from Frank at Keenlab. I had never removed and replaced parts on a circuit board before but after some you tube it worked out well.

          This is is also the first welder I’ve used, apparently I can break it and fix it, works for me.

          I’m going to check out that link above, thanks


            @Todd, thanks for your review here!

            For some unknown reason I didn't receive any notifications from this thread until just now.

            I hope that works again now, so please feel free to ask me any questions regarding my kWeld design.


            Todd is right, this is a DIY product without an expressed warranty. But if it breaks, then I will do my best to support my customers. If it is a production fault, like in Todd's case, then I will repair it free of charge and also carry shipping costs. Thanks to Todd's ability and generousity we found an easier way this time. If it is clear that it got damaged from misuse, for example by shorting one of the electrodes to the logic board, then I will still be happy to repair it, but ask for component cost and return shipping.

            Last edited by tatus1969; 02-12-2018, 02:16 AM.


            • Scoonie
              Scoonie commented
              Editing a comment
              Your commitment to support is very true. I know of two incidents where you stood tall and made the fix for the cost of shipping. A great unit!

            • Marin
              Marin commented
              Editing a comment
              cheers Frank

            I apologize for posting these units for sale and then not staying up to date and checking-in regularly. I will do better from here on out. I have been working 12-hour shifts at work, and last month I worked a month straight because one guy quit and another went to the hospital with a Krohns flare-up. That is no excuse, I could have still checked in here.

            I am selling the kWeld unit for slightly less than you can buy them from Germany. I am able to do this because I have made a bulk purchase and that saves on the per-unit shipping cost from Germany, and it also saves on the customs fees. I am selling these units for $229 plus $19 shipping (USPS). This is the same exact unit that Frank is selling from Germany, and I am only shipping within the USA.

            When the first batch were finally ready to ship from Germany, I had received a lot of interest in these, so I purchased 20 units, instead of the ten I originally reserved. I now have eight units left (12 sold). When they run out, I can purchase more at this price.

            One buyer realized that it was really more money than he wanted to spend, and he probably wouldn't actually use it, so...I refunded his payment, minus the shipping cost...once the unit was returned to me. ES member "Marin" experienced a blown diode, appears it was a simple manufacturing defect, so Frank sent him a new diode with instructions on how to swap them out. Marins' kWeld is back to working again.

            The initial reports of the performance are very good. I have been very frustrated that I have not been able to play with my own kWeld yet. All of the first 20 units I have purchased come with a 100% money-back guarantee, no questions asked. I simply want to facilitate getting some of these into the hands of real experimenters, so we can see what they can do.

            If you want to experiment with a kWeld spot-welder, you can contact me at, and please put "kWeld" somewhere in the email title so the spam filter doesn't hide it from me. I am located in Kansas, and a typical shipping arrival would be four days from payment (plus or minus).


              I just used my new KWeld today on a 14s5p pack. This is after practicing on 6 dead cells to get the feel for the welder. Overall, I’m very happy.

              After assembling the unit that spinningmagnets kindly sold and shipped to me I decided to go with a big lead acid 12v 720a power source. The settings are very easy to figure out, and it’s very nice that it’s all controlled with one knob. Turn it as needed, and press it when needed.

              My first practice welds were with .15 x 8mm pure nickel strips. I tried the power level at 100j, and I proceeded to melt large holes in the nickel. After scaling back I found that 35j worked perfectly for strip to cell. I used 40j when I overlapped strips on a cell.

              I’m right handed, and my left hand is very clumsy. On my very first real weld on PF cells, my left hand slipped causing the electrodes to make contact as the charge hit. I got a hole in the nickel, and I also got some clear battery goo hissing out of the negative end. Ive built quite a few packs, and this is the first time that happened to me, ever. It scared the crap out of me because of the firm respect I have for these little cells. So after that I made sure to plant the left one and then the right, and all was fine.

              I liked using the auto mode. When both electrodes made contact, the machine made a nice little wind-up sound, and then the cables jumped as it delivered the power. A solid beep confirms that it was a good weld. Unlike a stationary spot welder, I was able to put the entire pack together before making and welds because the leads for the electrodes allow a wide range of motion over my work area. This cut welding time dramatically, and it will be especially helpful with larger packs.

              My biggest complaint (and maybe I’m asking too much) is that the electrodes got very hot, and I had to allow cooldown periodically. This frustrated me a bit because I was really enjoying the fast rate of welds I could make.

              The 1/4” copper tips were a little loose in the connector, but I fixed that by sweating some solder into the gaps of each. I put a few more layers of heat shrink around each end as well to provide a better grip, and to help insulate the heat from my fingers. I wear medium weight runner gloves, and it although it wasn’t super comfortable to hold each electrode, it still worked quite well. The heat was what eventually got to me though, as stated before.

              I’m not sure if I’m pushing the machine too much by working until the electrodes get so hot, so if anyone can chime in on that I’d appreciate it. I really want this welder to last a long time, as I am already very fond of it. Perhaps I’ll make a second set of electrodes and simply swap them out when they heat up.

              So that’s my 2 cents. I highly recommend this welder to everyone who’s thinking about buying a cheap Chinese (Sunko) or other machine. It’s not even that much more expensive, and it delivers a whole lot more. Plus I image that it will far outlast a cheap machine, and parts are easy to see and replace as needed.