I’ve been in the process of building a 14S7P 18650 GA 50 Amp Cont soft pack for some time now. In the process I’ve learned a whole lot about battery building and exactly how challenging it can be. Once of the real struggles I’ve had is finding a decent battery spot welder that doesn’t break the bank. For this project, I ended up using 2 different battery spot welders, both purchased from eBay. This article will discuss the pros and cons of both welders as well as making suggestions of what you shouldn’t waste your money on.
This is the first spot welder I purchased off ebay, it was not worth the $126 I paid for it
The first spot welder I purchased was off eBay since that was the cheapest place I could find. There are a plethora of welders out there on eBay and Aliexpress just search for “battery spot welders”. This welder had some serious limitations. The biggest problem I found was that the welding tips only go two cells deep. This works fine if you’re building a hot glue pack and can just glue on cells as you go, but if you are using a plastic stencil pack then it can be seriously difficult to build a large pack. The pack I was building used a total of 98 cells, was 5 cells deep and weighed about 12 lbs. It was incredibly difficult and fatiguing to try to spot weld that pack. I ended up bending the metal contacts so that it would go 3 cells deep, but it was very difficult to do that and often it would slip and make a big spark. The welds with this unit were very good, because the electricity did not have to travel very far, the power you set at the machine tends to be close to what you get on the welds. With the second welder I purchased with remote battery welding leads, I would only get about 1/2 the energy I set the welder at because of the long wires that the remote leads had.
You can bend the tips to get more reach with your leads
After using this first welder for a few hundred welds, blowing 3 fuses, and tripping the circuit breaker in my house several times the unit just died. Since it had been more than 30 days since I bought it there was really no recourse, I emailed ontheway_2012 on eBay who said I was out of luck. I would not buy from them again, nor would I recommend this welder even to someone I didn’t like. For giggles I took it apart and the inside construction of this unit was laughably bad. They used hot glue everywhere to hold things together and everything about the inside of this unit looked very sketchy.
The second spot welder I purchased for $239 from eBay didn’t totally suck and hasn’t died … yet
I finally decided to splurge as my pack was now half built, and not being very useful to me in that state. I ended up settling on a welder with remote leads because it was such a pain to have to hold the battery up for several hours on end while I was welding it. It was also very tricky getting that third row of welds in with the bent leads. This new welder was much nicer and even comes with a cheapo soldering iron which I have yet to test. You can use it with the leads on the box and weld it like you used the first welder by pushing the battery pack up and the welds automatically zapping the battery when there was adequate pressure. It also shipped with a foot switch which in tandem with the remote leads. At first, it was a little unnerving watching the lead wires jump every time I did a weld, but after a while I got used to it and was able to focus on the task at hand. I messed around with the settings but ended up setting it to 8 pulses with the power up at maximum with the remote leads. Full power is a complete overkill if you are using the leads mounted directly on the box because you end up getting a lot more of the power through the welds. It worked fine just a bit over 1/2 way up when welding cells using the pressure sensitive welding leads directly the box. Higher than that and you will start melting through the nickel strips.
Instead of doing multiple welds on same 18650 battery in quick succession I ended up doing one weld at a time on each battery and then jumping to the next one. The batteries got pretty hot from the welds and I was worried that the batteries would blow up in my face if they got too hot. Speaking of batteries blowing up in your face you should ALWAYS use eye protection when working with welding lithium batteries. If you don’t do this then really there is no hope for you. Really.
Hot glue, the construction material of choice for millions of Chinese electrical products. Ahhhh China.
The remote welding leads got very hot when I was doing too many welds in a row too quickly. At first, it was unsettling but it was a great way to get me to slow down. I suspect that I destroyed the first welder by doing too many welds too quickly and burned out something in the welder. When the first welder stopped working it would act like it was working but then it just wouldn’t actually weld. Kind of like me, at a real job. I would pretend to work as soon as the boss walked in, then as soon as they walked out, it was right back to the video games. That’s why I have to work for myself, because no one else can put up with me.
The one thing I’ve learned through the whole battery building process is that it’s really not worth your time and energy to undertake a battery building project. If you can find a decent 18650 pack already built then chances are it will be cheaper and less frustrating to just buy and use that battery than to try to make your own from scratch. If you’re interested in learning about how to build batteries yourself and are looking for a cool and fun ebike project, then by all means, you should do it, but if you’re looking to save money & time then you’re going to be disappointed. Kind of like the time I really, really wanted that Optimus Prime transformer for Christmas and then when I finally got it and realized it wasn’t a real living robot I cried myself to sleep.
Ride On.
UPDATE : I loaned the expensive battery welder to a friend of mine and the fuse blew, then after it was replaced the fuse holder actually melted. I guess you get what you pay for.
ElectricBike-Blog.com 
Thanks for another good read! Since batteries will need replacement every two years or so I think it’s definitely worth to build it yourself. The initial investment of tools and parts make the first battery a bit more expensive than if you bought it at the shop. The following packs are about 1/3 of that price. That being said, I love the fact that I’m now able to build batteries for my sailboat or future RV. That I’ve learned how to solder and understand battery chemistry, W, V and Ah. I also like how it tickels in my toes when I weld and knowing it’s my own pack laying there in my backpack propelling me to work every day.
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I was lucky enough after an Aliexpress ripoff to buy a JP Welder from a great Croatian lad. Works like a champ off a 12v car battery. Super for repairs and adequate for new builds. In the end if Luna has a similar pack available thats the better deal, but since 36V are largely unobtanium, I’m glad I can build my own
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Thank you for the article. Really now need to be ostarozhny buying such products, it is necessary to buy from reliable people.
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Thanks for the review. Very informative. I haven’t decided yet, whether I’m going to build batteries or not. I don’t have any electric vehicle projects. I do have an interest in emergency lighting, and perhaps building a solar charged battery bank with inverter for computer backup power.
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Too much can go wrong with that battery pack you bought with your hard earned money. Seems very wise to learn to rebuild the damaged pack or build from scratch saving money and heart ache.
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Would it be possible to weld 2 thin (0.005″) strips of brass together with this machine? I notice on one description of either this machine or a similar one that it cannot be used to weld copper or aluminum. I need something to tack some brass sheets together while I silver solder the joints to form a liquid seal. Thanks.
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I don’t know. Probably.
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What nickel strip did you end up using? I stupidly bought .2 x 8mm but the battery holder I’m using only has gaps for 6mm and my diy spot welder struggles with the thick nickel 😦
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Hi
Great reviews. I’m interested in that silver one, but all the reviews on Amazon suggest they pop fuses, pop circuit breakers and even pop RCDs which tells me these things are really badly put together. But the choice seems to be either one of these things < $200 or one of the "pro" ones that are $3000+
So I'm wondering what your experience is with RCDs and circuit breakers when using the SUNKKO one ?
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Yeah in that price range these units are garbage. They hot glue the pieces together inside. I have not had circuit breakers blow, but they are on independent 20 Amp circuits when I’m working. The fuse holder melted though….
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Hi,
I believe that the main reason that the welders pop CB’s & RCD’s is that they momentarily draw too much current for most domestic consumer units – some of the Sunkko ads even state that they are not suitable for home use. I had that trouble despite plugging into the cooker circuir @ home which had a32 amp RCD. I replaced the 32 amp RCD with a 50 amp one of the same brand and it has not popped since.
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Have the mongoose dolomite 7 speed, has too much resistance for my (lack of) stamina (age & heart ussues). Though with some assistance at appropriate times this would be a fun time with grands on bikeway and my coffee shop visits. Reading everthing ebike i can, and wanting to start my conversion with some learning tips from your group.
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I think you may find the K-weld spot welder is a tool worth the investment. I’m sure it’s on your radar by now, but here is a ES thread on it anyway https://endless-sphere.com/forums/viewtopic.php?t=89039. Also, have been meaning to thank you. About a year ago, stumbled onto a build article of yours here on a Google search. I was searching because i had interest but knew nothing about e-bikes. Your personality and life in the articles kept me reading, and that lead to me being a darn good Luna customer over this year, so i learned tons about bikes and putting together damn good e-bikes. It may have started some other way, but it all did start for me from reading you decided to play everyday in the snow. Thanks
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I couldn’t do it without people like you. Thanks for reading and contributing.
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Keeled is in its 3rd or 4th revision. While the first endless sphere version, the J P Welder rocks on. My keels needs shipped back for updates, my two JP keep on keeping on.
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You can certainly see your skills in the work you write. The world hopes for more passionate writers like you who are not afraid to say how they believe. Always follow your heart.
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how do I make these 18650 unprotected batteries suck less with BMS? glue?
sure, your story’s inspired answer is just buy a better protected battery and swap it out. Ok, then use spring tension to connect modules?
I really like the spot welded tab with lead on the battery I extracted from another device. 😦
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Awww poor little tyke. So sad about Optimus. I cried myself to not sleep after my babysitter let me stay up and watch American werewolf in London when I was about 9yrs old. When you think buddy wakes up and that nazi zombie thing jumps out of the curtains and knifes her up after a bunch of them off his family is still with me to this day 35yrs later. Bloody babysitter.
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Do you understand what “you get what you pay for ” means. Sure you do. what naive person would think you pay 100 for something that is worth a 1000. You get what you pay for is the best you can hope for…as opposed to paying 100 and getting 10 worth of material…gown up
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Nice bblog thanks for posting
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I’m ready to blow myself up. Ok so where do I start? I’m thinking I can yank out a microwave transformer and rewire the secondary’s on it to make whatever I’m trying to weld just melt on contact. Or, I can try soldering these batteries together with… I don’t know, uhm… lamp cord maybe. I been also thinking that its going to just take way to long to charge all these batteries before assembling them so heck with that. I’m living wild and dangerous. Just piece it together sound like a fun idea. So anyways I’m going to create a 96v 2,200ah battery and from what I’ve read running batteries in series gets me my voltage. that is 26 in series. Now for my amp hours I will need roughly about… I don’t know, uhm… anyone have the answer? I’ll figure it out later. But for now I better start collecting these batteries from all them old laptops at the electronic recycling center down the street and I’ll need me some dark clothing because I’m hopping the fence tonight at 2am. This is soo exciting, isn’t it?! I’m actually not spending much money at all either on this build. They have microwaves over there to so making a welder from a transformer is going to ne free, the batteries are going to be free and heck, if I manage to not get arrested I’ll be free to. anyways wish me luck gang.
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Be careful, a lot of people get messed up trying to build welders out of microwave transformers.
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